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- Committer: Bazaar Package Importer
- Author(s): Dirk Eddelbuettel
- Date: 2002-04-13 11:33:49 UTC
- Revision ID: james.westby@ubuntu.com-20020413113349-hl2r1t730b91ov68
Tags: upstream-1.06
Import upstream version 1.06
- files added:
- Examples
- Test
- bc
- dc
- doc
- h
- lib
added
removed
doc/bc.info
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This is bc.info, produced by makeinfo version 4.0 from bc.texi.
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File: bc.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
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* Menu:
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* Introduction::
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* Basic Elements::
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* Expressions::
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* Statements::
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* Functions::
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* Examples::
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* Readline and Libedit Options::
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* GNU `bc' and Other Implementations::
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* Limits::
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* Environment Variables::
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File: bc.info, Node: Introduction, Next: Basic Elements, Prev: Top, Up: Top
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Introduction
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************
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* Menu:
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* Description::
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* Command Line Options::
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File: bc.info, Node: Description, Next: Command Line Options, Prev: Introduction, Up: Introduction
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Description
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===========
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`bc' [ -hlwsqv ] [long-options] [ FILE ... ]
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`bc' is a language that supports arbitrary precision numbers with
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interactive execution of statements. There are some similarities in
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the syntax to the C programming language. A standard math library is
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available by command line option. If requested, the math library is
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defined before processing any files. `bc' starts by processing code
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from all the files listed on the command line in the order listed.
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After all files have been processed, `bc' reads from the standard
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input. All code is executed as it is read. (If a file contains a
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command to halt the processor, `bc' will never read from the standard
47
input.)
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49
This version of `bc' contains several extensions beyond traditional
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`bc' implementations and the POSIX draft standard. Command line
51
options can cause these extensions to print a warning or to be
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rejected. This document describes the language accepted by this
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processor. Extensions will be identified as such.
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55
The author would like to thank Steve Sommars
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(<Steve.Sommars@att.com>) for his extensive help in testing the
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implementation. Many great suggestions were given. This is a much
58
better product due to his involvement.
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Email bug reports to <bug-bc@gnu.org>. Be sure to include the word
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"bc" somewhere in the "Subject:" field.
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File: bc.info, Node: Command Line Options, Next: Numbers, Prev: Description, Up: Introduction
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Command Line Options
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====================
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`bc' takes the following options from the command line:
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`-h, --help'
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Print the usage and exit.
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`-l, --mathlib'
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Define the standard math library.
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`-w, --warn'
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Give warnings for extensions to POSIX `bc'.
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`-s, --standard'
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Process exactly the POSIX `bc' language.
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`-q, --quiet'
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Do not print the normal GNU `bc' welcome.
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`-v, --version'
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Print the version number and copyright and quit.
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File: bc.info, Node: Basic Elements, Next: Expressions, Prev: Introduction, Up: Top
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Basic Elements
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**************
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* Menu:
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* Numbers::
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* Variables::
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* Comments::
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File: bc.info, Node: Numbers, Next: Variables, Prev: Command Line Options, Up: Basic Elements
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Numbers
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=======
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The most basic element in `bc' is the number. Numbers are arbitrary
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precision numbers. This precision is both in the integer part and the
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fractional part. All numbers are represented internally in decimal and
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all computation is done in decimal. (This version truncates results
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from divide and multiply operations.) There are two attributes of
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numbers, the length and the scale. The length is the total number of
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significant decimal digits in a number and the scale is the total number
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of decimal digits after the decimal point. For example, .000001 has a
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length of 6 and scale of 6, while 1935.000 has a length of 7 and a scale
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of 3.
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File: bc.info, Node: Variables, Next: Comments, Prev: Numbers, Up: Basic Elements
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Variables
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=========
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Numbers are stored in two types of variables, simple variables and
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arrays. Both simple variables and array variables are named. Names
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begin with a letter followed by any number of letters, digits and
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underscores. All letters must be lower case. (Full alphanumeric names
127
are an extension. In POSIX `bc' all names are a single lower case
128
letter.) The type of variable is clear by the context because all
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array variable names will be followed by brackets ( [ ] ).
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There are four special variables, SCALE, IBASE, OBASE, and LAST.
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SCALE defines how some operations use digits after the decimal point.
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The default value of SCALE is 0. IBASE and OBASE define the conversion
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base for input and output numbers. The default for both input and
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output is base 10. LAST (an extension) is a variable that has the
136
value of the last printed number. These will be discussed in further
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detail where appropriate. All of these variables may have values
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assigned to them as well as used in expressions.
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File: bc.info, Node: Comments, Prev: Variables, Up: Basic Elements
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Comments
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========
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Comments in `bc' start with the characters `/*' and end with the
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characters `*/'. Comments may start anywhere and appear as a single
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space in the input. (This causes comments to delimit other input
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items. For example, a comment can not be found in the middle of a
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variable name.) Comments include any newlines (end of line) between
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the start and the end of the comment.
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To support the use of scripts for `bc', a single line comment has
154
been added as an extension. A single line comment starts at a `#'
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character and continues to the next end of the line. The end of line
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character is not part of the comment and is processed normally.
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File: bc.info, Node: Expressions, Next: Statements, Prev: Basic Elements, Up: Top
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Expressions
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***********
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* Menu:
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* About Expressions and Special Variables::
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* Basic Expressions::
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* Relational Expressions::
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* Boolean Expressions::
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* Precedence::
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* Special Expressions::
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File: bc.info, Node: About Expressions and Special Variables, Next: Basic Expressions, Prev: Expressions, Up: Expressions
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About Expressions and Special Variables
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=======================================
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The numbers are manipulated by expressions and statements. Since
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the language was designed to be interactive, statements and expressions
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are executed as soon as possible. There is no main program. Instead,
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code is executed as it is encountered. (Functions, discussed in detail
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later, are defined when encountered.)
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A simple expression is just a constant. `bc' converts constants into
186
internal decimal numbers using the current input base, specified by the
187
variable IBASE. (There is an exception in functions.) The legal values
188
of IBASE are 2 through 16. Assigning a value outside this range to
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IBASE will result in a value of 2 or 16. Input numbers may contain the
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characters 0-9 and A-F. (Note: They must be capitals. Lower case
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letters are variable names.) Single digit numbers always have the
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value of the digit regardless of the value of IBASE. (i.e. A = 10.)
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For multi-digit numbers, `bc' changes all input digits greater or equal
194
to IBASE to the value of IBASE-1. This makes the number `FFF' always
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be the largest 3 digit number of the input base.
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Full expressions are similar to many other high level languages.
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Since there is only one kind of number, there are no rules for mixing
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types. Instead, there are rules on the scale of expressions. Every
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expression has a scale. This is derived from the scale of original
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numbers, the operation performed and in many cases, the value of the
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variable SCALE. Legal values of the variable SCALE are 0 to the maximum
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number representable by a C integer.
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File: bc.info, Node: Basic Expressions, Next: Relational Expressions, Prev: About Expressions and Special Variables, Up: Expressions
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Basic Expressions
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=================
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In the following descriptions of legal expressions, "expr" refers to
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a complete expression and "VAR" refers to a simple or an array variable.
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A simple variable is just a
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NAME
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and an array variable is specified as
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219
NAME[EXPR]
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221
Unless specifically mentioned the scale of the result is the maximum
222
scale of the expressions involved.
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`- expr'
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The result is the negation of the expression.
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`++ VAR'
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The variable is incremented by one and the new value is the result
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of the expression.
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`-- VAR'
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The variable is decremented by one and the new value is the result
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of the expression.
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`VAR ++'
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The result of the expression is the value of the variable and then
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the variable is incremented by one.
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`VAR --'
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The result of the expression is the value of the variable and then
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the variable is decremented by one.
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`expr + expr'
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The result of the expression is the sum of the two expressions.
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`expr - expr'
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The result of the expression is the difference of the two
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expressions.
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`expr * expr'
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The result of the expression is the product of the two expressions.
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`expr / expr'
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The result of the expression is the quotient of the two
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expressions. The scale of the result is the value of the variable
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`scale'
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`expr % expr'
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The result of the expression is the "remainder" and it is computed
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in the following way. To compute a%b, first a/b is computed to
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SCALE digits. That result is used to compute a-(a/b)*b to the
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scale of the maximum of SCALE+scale(b) and scale(a). If SCALE is
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set to zero and both expressions are integers this expression is
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the integer remainder function.
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`expr ^ expr'
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The result of the expression is the value of the first raised to
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the second. The second expression must be an integer. (If the
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second expression is not an integer, a warning is generated and the
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expression is truncated to get an integer value.) The scale of the
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result is SCALE if the exponent is negative. If the exponent is
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positive the scale of the result is the minimum of the scale of the
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first expression times the value of the exponent and the maximum of
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SCALE and the scale of the first expression. (e.g. scale(a^b) =
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min(scale(a)*b, max(SCALE, scale(a))).) It should be noted that
276
expr^0 will always return the value of 1.
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`( expr )'
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This alters the standard precedence to force the evaluation of the
280
expression.
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`VAR = expr'
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The variable is assigned the value of the expression.
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`VAR <op>= expr'
286
This is equivalent to "VAR = VAR <op> expr" with the exception
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that the "VAR" part is evaluated only once. This can make a
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difference if "VAR" is an array.
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File: bc.info, Node: Relational Expressions, Next: Boolean Expressions, Prev: Basic Expressions, Up: Expressions
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Relational Expressions
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======================
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Relational expressions are a special kind of expression that always
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evaluate to 0 or 1, 0 if the relation is false and 1 if the relation is
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true. These may appear in any legal expression. (POSIX `bc' requires
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that relational expressions are used only in `if', `while', and `for'
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statements and that only one relational test may be done in them.) The
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relational operators are
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`expr1 < expr2'
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The result is 1 if expr1 is strictly less than expr2.
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`expr1 <= expr2'
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The result is 1 if expr1 is less than or equal to expr2.
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`expr1 > expr2'
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The result is 1 if expr1 is strictly greater than expr2.
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`expr1 >= expr2'
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The result is 1 if expr1 is greater than or equal to expr2.
314
315
`expr1 == expr2'
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The result is 1 if expr1 is equal to expr2.
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`expr1 != expr2'
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The result is 1 if expr1 is not equal to expr2.
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File: bc.info, Node: Boolean Expressions, Next: Precedence, Prev: Relational Expressions, Up: Expressions
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Boolean Expressions
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===================
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Boolean operations are also legal. (POSIX `bc' does NOT have
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boolean operations). The result of all boolean operations are 0 and 1
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(for false and true) as in relational expressions. The boolean
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operators are:
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`!expr'
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The result is 1 if expr is 0.
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`expr && expr'
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The result is 1 if both expressions are non-zero.
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`expr || expr'
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The result is 1 if either expression is non-zero.
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File: bc.info, Node: Precedence, Next: Special Expressions, Prev: Boolean Expressions, Up: Expressions
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Precedence
345
==========
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The expression precedence is as follows: (lowest to highest)
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|| operator, left associative
350
&& operator, left associative
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! operator, nonassociative
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Relational operators, left associative
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Assignment operator, right associative
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+ and - operators, left associative
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*, / and % operators, left associative
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^ operator, right associative
357
unary - operator, nonassociative
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++ and -- operators, nonassociative
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360
This precedence was chosen so that POSIX compliant `bc' programs
361
will run correctly. This will cause the use of the relational and
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logical operators to have some unusual behavior when used with
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assignment expressions. Consider the expression:
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a = 3 < 5
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Most C programmers would assume this would assign the result of "3 <
368
5" (the value 1) to the variable "a". What this does in `bc' is assign
369
the value 3 to the variable "a" and then compare 3 to 5. It is best to
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use parentheses when using relational and logical operators with the
371
assignment operators.
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File: bc.info, Node: Special Expressions, Prev: Precedence, Up: Expressions
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Special Expressions
377
===================
378
379
There are a few more special expressions that are provided in `bc'.
380
These have to do with user-defined functions and standard functions.
381
They all appear as "NAME`('PARAMETERS`)'". *Note Functions::, for
382
user-defined functions. The standard functions are:
383
384
`length ( expression )'
385
The value of the length function is the number of significant
386
digits in the expression.
387
388
`read ( )'
389
The `read' function (an extension) will read a number from the
390
standard input, regardless of where the function occurs. Beware,
391
this can cause problems with the mixing of data and program in the
392
standard input. The best use for this function is in a previously
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written program that needs input from the user, but never allows
394
program code to be input from the user. The value of the `read'
395
function is the number read from the standard input using the
396
current value of the variable IBASE for the conversion base.
397
398
`scale ( expression )'
399
The value of the `scale' function is the number of digits after the
400
decimal point in the expression.
401
402
`sqrt ( expression )'
403
The value of the `sqrt' function is the square root of the
404
expression. If the expression is negative, a run time error is
405
generated.
406
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File: bc.info, Node: Statements, Next: Functions, Prev: Expressions, Up: Top
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Statements
411
**********
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* Menu:
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* Pseudo Statements::
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Statements (as in most algebraic languages) provide the sequencing of
418
expression evaluation. In `bc' statements are executed "as soon as
419
possible." Execution happens when a newline in encountered and there
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is one or more complete statements. Due to this immediate execution,
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newlines are very important in `bc'. In fact, both a semicolon and a
422
newline are used as statement separators. An improperly placed newline
423
will cause a syntax error. Because newlines are statement separators,
424
it is possible to hide a newline by using the backslash character. The
425
sequence "\<nl>", where <nl> is the newline appears to `bc' as
426
whitespace instead of a newline. A statement list is a series of
427
statements separated by semicolons and newlines. The following is a
428
list of `bc' statements and what they do: (Things enclosed in brackets
429
( [ ] ) are optional parts of the statement.)
430
431
EXPRESSION
432
This statement does one of two things. If the expression starts
433
with "<variable> <assignment> ...", it is considered to be an
434
assignment statement. If the expression is not an assignment
435
statement, the expression is evaluated and printed to the output.
436
After the number is printed, a newline is printed. For example,
437
"a=1" is an assignment statement and "(a=1)" is an expression that
438
has an embedded assignment. All numbers that are printed are
439
printed in the base specified by the variable OBASE. The legal
440
values for OBASE are 2 through BC_BASE_MAX (*note Environment
441
Variables::). For bases 2 through 16, the usual method of writing
442
numbers is used. For bases greater than 16, `bc' uses a
443
multi-character digit method of printing the numbers where each
444
higher base digit is printed as a base 10 number. The
445
multi-character digits are separated by spaces. Each digit
446
contains the number of characters required to represent the base
447
ten value of "OBASE -1". Since numbers are of arbitrary
448
precision, some numbers may not be printable on a single output
449
line. These long numbers will be split across lines using the "\"
450
as the last character on a line. The maximum number of characters
451
printed per line is 70. Due to the interactive nature of `bc',
452
printing a number causes the side effect of assigning the printed
453
value to the special variable LAST. This allows the user to
454
recover the last value printed without having to retype the
455
expression that printed the number. Assigning to LAST is legal
456
and will overwrite the last printed value with the assigned value.
457
The newly assigned value will remain until the next number is
458
printed or another value is assigned to LAST. (Some installations
459
may allow the use of a single period (.) which is not part of a
460
number as a short hand notation for for LAST.)
461
462
STRING
463
The string is printed to the output. Strings start with a double
464
quote character and contain all characters until the next double
465
quote character. All characters are taken literally, including
466
any newline. No newline character is printed after the string.
467
468
`PRINT' LIST
469
The `print' statement (an extension) provides another method of
470
output. The LIST is a list of strings and expressions separated by
471
commas. Each string or expression is printed in the order of the
472
list. No terminating newline is printed. Expressions are
473
evaluated and their value is printed and assigned to the variable
474
`last'. Strings in the print statement are printed to the output
475
and may contain special characters. Special characters start with
476
the backslash character (\e). The special characters recognized
477
by `bc' are "a" (alert or bell), "b" (backspace), "f" (form feed),
478
"n" (newline), "r" (carriage return), "q" (double quote), "t"
479
(tab), and "\e" (backslash). Any other character following the
480
backslash will be ignored.
481
482
{ STATEMENT_LIST }
483
This is the compound statement. It allows multiple statements to
484
be grouped together for execution.
485
486
`IF' ( EXPRESSION ) STATEMENT1 [`ELSE' STATEMENT2]
487
The if statement evaluates the expression and executes statement1
488
or statement2 depending on the value of the expression. If the
489
expression is non-zero, statement1 is executed. If statement2 is
490
present and the value of the expression is 0, then statement2 is
491
executed. (The `else' clause is an extension.)
492
493
`WHILE' ( EXPRESSION ) STATEMENT
494
The while statement will execute the statement while the expression
495
is non-zero. It evaluates the expression before each execution of
496
the statement. Termination of the loop is caused by a zero
497
expression value or the execution of a `break' statement.
498
499
`FOR' ( [EXPRESSION1] ; [EXPRESSION2] ; [EXPRESSION3] ) STATEMENT
500
The `for' statement controls repeated execution of the statement.
501
EXPRESSION1 is evaluated before the loop. EXPRESSION2 is
502
evaluated before each execution of the statement. If it is
503
non-zero, the statement is evaluated. If it is zero, the loop is
504
terminated. After each execution of the statement, EXPRESSION3 is
505
evaluated before the reevaluation of expression2. If EXPRESSION1
506
or EXPRESSION3 are missing, nothing is evaluated at the point they
507
would be evaluated. If EXPRESSION2 is missing, it is the same as
508
substituting the value 1 for EXPRESSION2. (The optional
509
expressions are an extension. POSIX `bc' requires all three
510
expressions.) The following is equivalent code for the `for'
511
statement:
512
513
expression1;
514
while (expression2) {
515
statement;
516
expression3;
517
}
518
519
`BREAK'
520
This statement causes a forced exit of the most recent enclosing
521
`while' statement or `for' statement.
522
523
`CONTINUE'
524
The `continue' statement (an extension) causes the most recent
525
enclosing `for' statement to start the next iteration.
526
527
`HALT'
528
The `halt' statement (an extension) is an executed statement that
529
causes the `bc' processor to quit only when it is executed. For
530
example, "if (0 == 1) halt" will not cause `bc' to terminate
531
because the `halt' is not executed.
532
533
`RETURN'
534
Return the value 0 from a function. (*Note Functions::.)
535
536
`RETURN' ( EXPRESSION )
537
Return the value of the expression from a function. (*Note
538
Functions::.) As an extension, the parenthesis are not required.
539
540
541
File: bc.info, Node: Pseudo Statements, Prev: Statements, Up: Statements
542
543
Pseudo Statements
544
=================
545
546
These statements are not statements in the traditional sense. They
547
are not executed statements. Their function is performed at "compile"
548
time.
549
550
`limits'
551
Print the local limits enforced by the local version of `bc'. This
552
is an extension.
553
554
`quit'
555
When the `quit' statement is read, the `bc' processor is
556
terminated, regardless of where the `quit' statement is found. For
557
example, "if (0 == 1) quit" will cause `bc' to terminate.
558
559
`warranty'
560
Print a longer warranty notice. This is an extension.
561
562
563
File: bc.info, Node: Functions, Next: Examples, Prev: Statements, Up: Top
564
565
Functions
566
*********
567
568
* Menu:
569
570
* Math Library Functions::
571
572
Functions provide a method of defining a computation that can be
573
executed later. Functions in `bc' always compute a value and return it
574
to the caller. Function definitions are "dynamic" in the sense that a
575
function is undefined until a definition is encountered in the input.
576
That definition is then used until another definition function for the
577
same name is encountered. The new definition then replaces the older
578
definition. A function is defined as follows:
579
580
`define' NAME `(' PARAMETERS `)' `{' NEWLINE
581
AUTO_LIST STATEMENT_LIST `}'
582
583
A function call is just an expression of the form "`name'
584
`('PARAMETERS`)'".
585
586
Parameters are numbers or arrays (an extension). In the function
587
definition, zero or more parameters are defined by listing their names
588
separated by commas. Numbers are only call by value parameters.
589
Arrays are only call by variable. Arrays are specified in the
590
parameter definition by the notation "NAME`[ ]'". In the function
591
call, actual parameters are full expressions for number parameters.
592
The same notation is used for passing arrays as for defining array
593
parameters. The named array is passed by variable to the function.
594
Since function definitions are dynamic, parameter numbers and types are
595
checked when a function is called. Any mismatch in number or types of
596
parameters will cause a runtime error. A runtime error will also occur
597
for the call to an undefined function.
598
599
The AUTO_LIST is an optional list of variables that are for "local"
600
use. The syntax of the auto list (if present) is "`auto' NAME, ... ;".
601
(The semicolon is optional.) Each NAME is the name of an auto
602
variable. Arrays may be specified by using the same notation as used
603
in parameters. These variables have their values pushed onto a stack
604
at the start of the function. The variables are then initialized to
605
zero and used throughout the execution of the function. At function
606
exit, these variables are popped so that the original value (at the
607
time of the function call) of these variables are restored. The
608
parameters are really auto variables that are initialized to a value
609
provided in the function call. Auto variables are different than
610
traditional local variables because if function A calls function B, B
611
may access function A's auto variables by just using the same name,
612
unless function B has called them auto variables. Due to the fact that
613
auto variables and parameters are pushed onto a stack, `bc' supports
614
recursive functions.
615
616
The function body is a list of `bc' statements. Again, statements
617
are separated by semicolons or newlines. Return statements cause the
618
termination of a function and the return of a value. There are two
619
versions of the return statement. The first form, "`return'", returns
620
the value 0 to the calling expression. The second form, "`return' (
621
EXPRESSION )", computes the value of the expression and returns that
622
value to the calling expression. There is an implied "`return' (0)" at
623
the end of every function. This allows a function to terminate and
624
return 0 without an explicit `return' statement.
625
626
Functions also change the usage of the variable IBASE. All
627
constants in the function body will be converted using the value of
628
IBASE at the time of the function call. Changes of IBASE will be
629
ignored during the execution of the function except for the standard
630
function `read', which will always use the current value of IBASE for
631
conversion of numbers.
632
633
As an extension, the format of the definition has been slightly
634
relaxed. The standard requires the opening brace be on the same line
635
as the `define' keyword and all other parts must be on following lines.
636
This version of `bc' will allow any number of newlines before and after
637
the opening brace of the function. For example, the following
638
definitions are legal.
639
640
define d (n) { return (2*n); }
641
define d (n)
642
{ return (2*n); }
643
644
645
File: bc.info, Node: Math Library Functions, Prev: Functions, Up: Functions
646
647
Math Library Functions
648
======================
649
650
If `bc' is invoked with the `-l' option, a math library is preloaded
651
and the default SCALE is set to 20. The math functions will calculate
652
their results to the scale set at the time of their call. The math
653
library defines the following functions:
654
655
`s (X)'
656
The sine of X, X is in radians.
657
658
`c (X)'
659
The cosine of X, X is in radians.
660
661
`a (X)'
662
The arctangent of X, arctangent returns radians.
663
664
`l (X)'
665
The natural logarithm of X.
666
667
`E (X)'
668
The exponential function of raising E to the value X.
669
670
`J (N,X)'
671
The bessel function of integer order N of X.
672
673
674
File: bc.info, Node: Examples, Next: Readline and Libedit Options, Prev: Functions, Up: Top
675
676
Examples
677
********
678
679
In /bin/sh, the following will assign the value of "pi" to the shell
680
variable PI.
681
682
pi=$(echo "scale=10; 4*a(1)" | bc -l)
683
684
The following is the definition of the exponential function used in
685
the math library. This function is written in POSIX `bc'.
686
687
688
scale = 20
689
690
/* Uses the fact that e^x = (e^(x/2))^2
691
When x is small enough, we use the series:
692
e^x = 1 + x + x^2/2! + x^3/3! + ...
693
*/
694
695
define e(x) {
696
auto a, d, e, f, i, m, v, z
697
698
/* Check the sign of x. */
699
if (x<0) {
700
m = 1
701
x = -x
702
}
703
704
/* Precondition x. */
705
z = scale;
706
scale = 4 + z + .44*x;
707
while (x > 1) {
708
f += 1;
709
x /= 2;
710
}
711
712
/* Initialize the variables. */
713
v = 1+x
714
a = x
715
d = 1
716
717
for (i=2; 1; i++) {
718
e = (a *= x) / (d *= i)
719
if (e == 0) {
720
if (f>0) while (f--) v = v*v;
721
scale = z
722
if (m) return (1/v);
723
return (v/1);
724
}
725
v += e
726
}
727
}
728
729
The following is code that uses the extended features of `bc' to
730
implement a simple program for calculating checkbook balances. This
731
program is best kept in a file so that it can be used many times
732
without having to retype it at every use.
733
734
735
scale=2
736
print "\nCheck book program\n!"
737
print " Remember, deposits are negative transactions.\n"
738
print " Exit by a 0 transaction.\n\n"
739
740
print "Initial balance? "; bal = read()
741
bal /= 1
742
print "\n"
743
while (1) {
744
"current balance = "; bal
745
"transaction? "; trans = read()
746
if (trans == 0) break;
747
bal -= trans
748
bal /= 1
749
}
750
quit
751
752
The following is the definition of the recursive factorial function.
753
754
755
define f (x) {
756
if (x <= 1) return (1);
757
return (f(x-1) * x);
758
}
759
760
761
File: bc.info, Node: Readline and Libedit Options, Next: GNU `bc' and Other Implementations, Prev: Examples, Up: Top
762
763
Readline and Libedit Options
764
****************************
765
766
GNU `bc' can be compiled (via a configure option) to use the GNU
767
`readline' input editor library or the BSD `libedit' library. This
768
allows the user to do more editing of lines before sending them to
769
`bc'. It also allows for a history of previous lines typed. When this
770
option is selected, `bc' has one more special variable. This special
771
variable, HISTORY is the number of lines of history retained. A value
772
of -1 means that an unlimited number of history lines are retained.
773
This is the default value. Setting the value of HISTORY to a positive
774
number restricts the number of history lines to the number given. The
775
value of 0 disables the history feature. For more information, read
776
the user manuals for the GNU `readline', `history' and BSD `libedit'
777
libraries. One can not enable both `readline' and `libedit' at the
778
same time.
779
780
781
File: bc.info, Node: GNU `bc' and Other Implementations, Next: Limits, Prev: Readline and Libedit Options, Up: Top
782
783
GNU `bc' and Other Implementations
784
**********************************
785
786
This version of `bc' was implemented from the POSIX P1003.2/D11
787
draft and contains several differences and extensions relative to the
788
draft and traditional implementations. It is not implemented in the
789
traditional way using `dc'. This version is a single process which
790
parses and runs a byte code translation of the program. There is an
791
"undocumented" option (-c) that causes the program to output the byte
792
code to the standard output instead of running it. It was mainly used
793
for debugging the parser and preparing the math library.
794
795
A major source of differences is extensions, where a feature is
796
extended to add more functionality and additions, where new features
797
are added. The following is the list of differences and extensions.
798
799
LANG ENVIRONMENT
800
This version does not conform to the POSIX standard in the
801
processing of the LANG environment variable and all environment
802
variables starting with LC_.
803
804
NAMES
805
Traditional and POSIX `bc' have single letter names for functions,
806
variables and arrays. They have been extended to be
807
multi-character names that start with a letter and may contain
808
letters, numbers and the underscore character.
809
810
STRINGS
811
Strings are not allowed to contain NUL characters. POSIX says all
812
characters must be included in strings.
813
814
LAST
815
POSIX `bc' does not have a \fBlast variable. Some implementations
816
of `bc' use the period (.) in a similar way.
817
818
COMPARISONS
819
POSIX `bc' allows comparisons only in the `if' statement, the
820
`while' statement, and the second expression of the `for'
821
statement. Also, only one relational operation is allowed in each
822
of those statements.
823
824
IF STATEMENT, ELSE CLAUSE
825
POSIX `bc' does not have an `else' clause.
826
827
FOR STATEMENT
828
POSIX `bc' requires all expressions to be present in the `for'
829
statement.
830
831
&&, ||, !
832
POSIX `bc' does not have the logical operators.
833
834
READ FUNCTION
835
POSIX `bc' does not have a `read' function.
836
837
PRINT STATEMENT
838
POSIX `bc' does not have a `print' statement.
839
840
CONTINUE STATEMENT
841
POSIX `bc' does not have a continue statement.
842
843
ARRAY PARAMETERS
844
POSIX `bc' does not (currently) support array parameters in full.
845
The POSIX grammar allows for arrays in function definitions, but
846
does not provide a method to specify an array as an actual
847
parameter. (This is most likely an oversight in the grammar.)
848
Traditional implementations of `bc' have only call by value array
849
parameters.
850
851
FUNCTION FORMAT
852
POSIX `bc' requires the opening brace on the same line as the
853
`define' key word and the `auto' statement on the next line.
854
855
=+, =-, =*, =/, =%, =^
856
POSIX `bc' does not require these "old style" assignment operators
857
to be defined. This version may allow these "old style"
858
assignments. Use the `limits' statement to see if the installed
859
version supports them. If it does support the "old style"
860
assignment operators, the statement "a =- 1" will decrement `a' by
861
1 instead of setting `a' to the value -1.
862
863
SPACES IN NUMBERS
864
Other implementations of `bc' allow spaces in numbers. For
865
example, "x=1 3" would assign the value 13 to the variable x. The
866
same statement would cause a syntax error in this version of `bc'.
867
868
ERRORS AND EXECUTION
869
This implementation varies from other implementations in terms of
870
what code will be executed when syntax and other errors are found
871
in the program. If a syntax error is found in a function
872
definition, error recovery tries to find the beginning of a
873
statement and continue to parse the function. Once a syntax error
874
is found in the function, the function will not be callable and
875
becomes undefined. Syntax errors in the interactive execution
876
code will invalidate the current execution block. The execution
877
block is terminated by an end of line that appears after a
878
complete sequence of statements. For example,
879
880
a = 1
881
b = 2
882
883
has two execution blocks and
884
885
{ a = 1
886
b = 2 }
887
888
has one execution block. Any runtime error will terminate the
889
execution of the current execution block. A runtime warning will
890
not terminate the current execution block.
891
892
INTERRUPTS
893
During an interactive session, the SIGINT signal (usually
894
generated by the control-C character from the terminal) will cause
895
execution of the current execution block to be interrupted. It
896
will display a "runtime" error indicating which function was
897
interrupted. After all runtime structures have been cleaned up, a
898
message will be printed to notify the user that `bc' is ready for
899
more input. All previously defined functions remain defined and
900
the value of all non-auto variables are the value at the point of
901
interruption. All auto variables and function parameters are
902
removed during the clean up process. During a non-interactive
903
session, the SIGINT signal will terminate the entire run of `bc'.
904
905
906
File: bc.info, Node: Limits, Next: Environment Variables, Prev: GNU `bc' and Other Implementations, Up: Top
907
908
Limits
909
******
910
911
The following are the limits currently in place for this `bc'
912
processor. Some of them may have been changed by an installation. Use
913
the `limits' statement to see the actual values.
914
915
`BC_BASE_MAX'
916
The maximum output base is currently set at 999. The maximum
917
input base is 16.
918
919
`BC_DIM_MAX'
920
This is currently an arbitrary limit of 65535 as distributed. Your
921
installation may be different.
922
923
`BC_SCALE_MAX'
924
The number of digits after the decimal point is limited to INT_MAX
925
digits. Also, the number of digits before the decimal point is
926
limited to INT_MAX digits.
927
928
`BC_STRING_MAX'
929
The limit on the number of characters in a string is INT_MAX
930
characters.
931
932
`exponent'
933
The value of the exponent in the raise operation (^) is limited to
934
LONG_MAX.
935
936
`multiply'
937
The multiply routine may yield incorrect results if a number has
938
more than LONG_MAX / 90 total digits. For 32 bit longs, this
939
number is 23,860,929 digits.
940
941
`variable names'
942
The current limit on the number of unique names is 32767 for each
943
of simple variables, arrays and functions.
944
945
946
File: bc.info, Node: Environment Variables, Prev: Limits, Up: Top
947
948
Environment Variables
949
*********************
950
951
The following environment variables are processed by `bc':
952
953
`POSIXLY_CORRECT'
954
This is the same as the -s option (*note Command Line Options::).
955
956
`BC_ENV_ARGS'
957
This is another mechanism to get arguments to `bc'. The format is
958
the same as the command line arguments. These arguments are
959
processed first, so any files listed in the environent arguments
960
are processed before any command line argument files. This allows
961
the user to set up "standard" options and files to be processed at
962
every invocation of `bc'. The files in the environment variables
963
would typically contain function definitions for functions the user
964
wants defined every time `bc' is run.
965
966
`BC_LINE_LENGTH'
967
This should be an integer specifing the number of characters in an
968
output line for numbers. This includes the backslash and newline
969
characters for long numbers.
970
971
972
973
Tag Table:
974
Node: Top65
975
Node: Introduction354
976
Node: Description515
977
Node: Command Line Options1969
978
Node: Basic Elements2533
979
Node: Numbers2704
980
Node: Variables3467
981
Node: Comments4576
982
Node: Expressions5317
983
Node: About Expressions and Special Variables5597
984
Node: Basic Expressions7333
985
Node: Relational Expressions10274
986
Node: Boolean Expressions11279
987
Node: Precedence11834
988
Node: Special Expressions12994
989
Node: Statements14376
990
Node: Pseudo Statements21001
991
Node: Functions21649
992
Node: Math Library Functions25703
993
Node: Examples26413
994
Node: Readline and Libedit Options28431
995
Node: GNU `bc' and Other Implementations29458
996
Node: Limits34700
997
Node: Environment Variables35953
998
999
End Tag Table
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