1
Specifications of SigScheme
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===========================
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Supports LL64, LLP64, LP64 and ILP64 on both storage-fatty and storage-compact.
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Addressable memory space
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~~~~~~~~~~~~~~~~~~~~~~~~
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Ordinary storage implementation can address any Scheme object scattered on
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whole memory space. Both storage-fatty and storage-compact have no
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limitation on any 32 and 64-bit data models. But it may be limited if a
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storage implementation is designed to do so for some specific advantages,
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as like GNU Emacs' 28-bit tagged pointer does.
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Current implementation only supports fixnum, and its range varies by the
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user-selected underlying storage implementation. The range can be known via
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R6RS (R5.91RS) compatible `(fixnum-width)`, `(least-fixnum)` and
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Supported. But the conformance of `eval` procedure is uncertain. See the
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comments of `scm_p_eval()` and `rec-by-eval` of `test-tail-rec.scm` for further
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information about `eval`.
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Limited to nested use due to its setjmp/longjmp implementation. If a
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continuation that is not an ancestor of current continuation called, all
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continuation objects lying between the curent and the common ancestor of
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the destination are invalidated. Calling an invalidated continuation object
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The hygienic macros are fully supported. But although the macro expansion
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engine itself works well and can be expected as R5RS-conformant, its
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integration into SigScheme is not fully validated yet. It is likely having a
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problem on identifier references.
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SigScheme supports only the integer part of the numerical tower.
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SigScheme recognizes only these limited part of numerical forms of "7.1.1
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Lexical structure" section of R5RS. Other valid R5RS forms for numbers produce
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----------------------------------------------------------------
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<number> --> <num 2>| <num 8>
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<num R> --> <prefix R> <complex R>
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<complex R> --> <real R>
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<real R> --> <sign> <ureal R>
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<ureal R> --> <uinteger R>
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<uinteger R> --> <digit R>+ #* ;; '#' must not occur
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<prefix R> --> <radix R>
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<sign> --> <empty> | + | -
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<radix 10> --> <empty> | #d
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<digit 8> --> 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7
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<digit 10> --> <digit>
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<digit 16> --> <digit 10> | a | b | c | d | e | f
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<digit> --> 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
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----------------------------------------------------------------
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SigScheme accepts only lower case alphabets as radices as follows. But
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hexadecimal digits can be written as either lower or upper.
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----------------------------------------------------------------
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----------------------------------------------------------------
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SigScheme uses a fixed-size buffer for number literals parsing. Due to the
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implementation, it can accept only one optional '0' prefix for maximum-length
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binary number literals. Two or more '0' prefixes causes an error as follows.
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----------------------------------------------------------------
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;; storage-compact on ILP32 env
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(greatest-fixnum) ==> 2147483647
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#b11111111000000001111111100000000 ==> 4278255360
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#b011111111000000001111111100000000 ==> 4278255360
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#b0011111111000000001111111100000000 ==> error
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#b00011111111000000001111111100000000 ==> error
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----------------------------------------------------------------
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The procedures '-' and '/' support following optional form.
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----------------------------------------------------------------
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6.2.5 Numerical operations
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optional procedure: - z1 z2 ...
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optional procedure: / z1 z2 ...
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----------------------------------------------------------------
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All character category-sensitive procedures and predicates (such as
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char-upcase) work correctly only in ASCII range. i.e. Neither Unicode
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processing specified in SRFI-75 nor other non-Unicode multibyte character
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processing are supported in such procedures/predicates.
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Case-insensitive character comparison
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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SigScheme's case-insensitive comparison conforms to the foldcase'ed
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comparison described in SRFI-75 and SRFI-13, although R5RS does not specify
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comparison between alphabetic and non-alphabetic char.
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See the description in operations.c for further details.
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Case-sensitive identifiers
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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SigScheme does distinguish letter case in indentifiers. Although case
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insensitivity is required in R5RS as follows, it is hard to accept for the
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----------------------------------------------------------------
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2. Lexical conventions
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Upper and lower case forms of a letter are never distinguished except
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within character and string constants. For example, `Foo' is the same
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identifier as `FOO', and #x1AB is the same number as #X1ab.
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----------------------------------------------------------------
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SigScheme treats string literals as constant as specified in R5RS.
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================================================================
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sscm> (string-set! "foo" 0 #\F)
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Error: in string-set!: attempted to modify immutable string: "foo"
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sscm> (string-set! (string-copy "foo") 0 #\F)
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================================================================
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SigScheme inhibits modification of constant list object by default as
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specified in R5RS, if the storage implementation suports it. storage-fatty
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supports it, but storage-compact does not due to no bit space for pair
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The behavior can be changed by `SCM_CONST_LIST_LITERAL`.
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----------------------------------------------------------------
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4.1.2 Literal expressions
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`(quote <datum>)' may be abbreviated as '<datum>. The two notations
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are equivalent in all respects.
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'#(a b c) ==> #(a b c)
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'(quote a) ==> (quote a)
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As noted in section 3.4 Storage model, it is an error to alter a
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constant (i.e. the value of a literal expression) using a mutation
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procedure like `set-car!' or `string-set!'.
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6.3.2 Pairs and lists
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procedure: set-car! pair obj
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Stores obj in the car field of pair. The value returned by `set-car!'
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(define (g) '(constant-list))
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(set-car! (g) 3) ==> error
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----------------------------------------------------------------
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SigScheme inhibits modification of constant vector object by default as
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specified in R5RS, if the storage implementation suports it. storage-fatty
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supports it, but storage-compact is not yet.
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The behavior can be changed by `SCM_CONST_VECTOR_LITERAL`.
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----------------------------------------------------------------
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procedure: vector-set! vector k obj
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(vector-set! '#(0 1 2) 1 "doe")
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==> error ; constant vector
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----------------------------------------------------------------
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SigScheme allows quote-less null list by default for convenience and
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performance. But it can be error as specified in R5RS, when `SCM_STRICT_R5RS`
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.SCM_STRICT_R5RS disabled
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================================================================
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================================================================
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.SCM_STRICT_R5RS enabled
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================================================================
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Error: eval: () is not a valid R5RS form. use '() instead
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================================================================
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Quote-less vector literal
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~~~~~~~~~~~~~~~~~~~~~~~~~
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Sigscheme inhibits quote-less vector literal by default, as specified in
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The behavior can be changed by `SCM_STRICT_VECTOR_FORM`.
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----------------------------------------------------------------
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Vectors are written using the notation #(obj ...). For example, a vector
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of length 3 containing the number zero in element 0, the list `(2 2 2 2)'
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in element 1, and the string `"Anna"' in element 2 can be written as
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#(0 (2 2 2 2) "Anna")
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Note that this is the external representation of a vector, not an
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expression evaluating to a vector. Like list constants, vector constants
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'#(0 (2 2 2 2) "Anna")
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==> #(0 (2 2 2 2) "Anna")
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----------------------------------------------------------------
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================================================================
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Error: eval: #() is not a valid R5RS form. use '#() instead
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================================================================
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Environment specifiers
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~~~~~~~~~~~~~~~~~~~~~~
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`(null-environment)` and `(scheme-report-environment)` does not return correct
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environemnt specified in R5RS. Current implementation returns same object
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of `(interaction-environment)`.
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SigScheme strictly conforms to the 'internal definitions' defined in R5RS
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(cited below) if `SCM_STRICT_DEFINE_PLACEMENT` is enabled (default). It can be
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disabled to get the syntax loosen, shrink the footprint and reduce runtime
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----------------------------------------------------------------
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5.2.2 Internal definitions
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Definitions may occur at the beginning of a <body> (that is, the body of a
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lambda, let, let*, letrec, let-syntax, or letrec-syntax expression or that of
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a definition of an appropriate form). Such definitions are known as internal
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definitions as opposed to the top level definitions described above.
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----------------------------------------------------------------
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Superfluous arguments
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~~~~~~~~~~~~~~~~~~~~~
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Superfluous or dotted arguments are strictly rejected as an error if
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`SCM_STRICT_ARGCHECK` is enabled. Otherwise ignored. Resource-sensitive
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apprication could disable it.
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.SCM_STRICT_ARGCHECK enabled
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================================================================
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sscm> (car '(1 2) 3 4)
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Error: in (function call): superfluous argument(s): (3 4)
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sscm> (symbol? 'foo . #t)
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Error: in (function call): improper argument list terminator: #t
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Error: in (reduction): improper argument list terminator: 5
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================================================================
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.SCM_STRICT_ARGCHECK disabled
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================================================================
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sscm> (car '(1 2) 3 4)
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sscm> (symbol? 'foo . #t)
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================================================================
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Syntaxes/procedures not implemented
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Following R5RS syntaxes and procedures are not implemented (yet).
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- *procedure:* complex? obj
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- *procedure:* real? obj
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- *procedure:* rational? obj
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- *procedure:* exact? z
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- *procedure:* inexact? z
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- *library procedure:* gcd n1 ...
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- *library procedure:* lcm n1 ...
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- *procedure:* numerator q
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- *procedure:* denominator q
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- *procedure:* floor x
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- *procedure:* ceiling x
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- *procedure:* truncate x
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- *procedure:* round x
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- *library procedure:* rationalize x y
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- *procedure:* asin z
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- *procedure:* acos z
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- *procedure:* atan z
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- *procedure:* atan y x
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- *procedure:* sqrt z
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- *procedure:* expt z1 z2
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- *procedure:* make-rectangular x1 x2
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- *procedure:* make-polar x3 x4
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- *procedure:* real-part z
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- *procedure:* imag-part z
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- *procedure:* magnitude z
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- *procedure:* angle z
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- *procedure:* exact->inexact z
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- *procedure:* inexact->exact z
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- *library syntax:* delay <expression>
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- *library procedure:* force promise
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- *optional procedure:* transcript-on filename
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- *optional procedure:* transcript-off
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Although a C implementation `module-srfi1.c` is existing, it is still broken
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and should not use for production codes. To get SRFI-1 working with SigScheme,
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use SLIB version of the library (will be made available after some
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SRFI-22 Running Scheme Scripts on Unix
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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SigScheme only supports the prelude line interpretation. All options written in
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the line are applied as same as commandline invocation of sscm. But the `main`
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procedure invocation is not supported (yet).
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.Prelude line is interpreted as follows
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================================================================
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#! /usr/bin/env sscm -C UTF-8
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==> Character encoding for the file is changed to UTF-8 temporarily.
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================================================================
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SRFI-23 Error Reporting Mechanism
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If srfi-34 is provided, the `error` procedure throws a SigScheme-specific error
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object in cooperate with "SRFI-34 Exception Handling for Programs". Otherwise
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it simply calls scm_fatal_error(). Since the error objects are represented as a
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list, be careful on catching an exception based on its type. If you want to
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distinguish the error objects from ordinary lists, use SigScheme-specific
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`%%error-object?` predicate.
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.Error objects are also caught as a list
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================================================================
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sscm> (guard (obj ((pair? obj) obj)) (error "reason" 1 2 3))
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#<error "reason" 1 2 3>
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================================================================
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.Error object internal
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================================================================
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sscm> (define err (guard (err (#t err)) (error "reason" 1 2 3)))
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#<error "reason" 1 2 3>
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(#<undef> . #<undef>)
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sscm> (%%error-object? err)
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================================================================
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SRFI-28 Basic Format Strings
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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SigScheme fully supports SRFI-28. A directive-less tilde at end of a format
455
string causes an error as same as the reference implementation of SRFI-28.
458
================================================================
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(format "~") ==> error
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(format "a~") ==> error
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================================================================
463
SRFI-38 External Representation for Data with Shared Structure
464
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Only `write-with-shared-structure` is implemented and
467
`read-with-shared-structure` is not. The optional alias `write/ss` described in
468
SRFI-38 is also defined. The optional `optarg` argument is simply ignored.
470
The shared index starts with #1 (not #0).
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.Shared index starts with #1
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================================================================
474
sscm> (define lst (list 'a 'b))
476
sscm> (set-cdr! lst lst)
480
================================================================
482
SRFI-48 Intermediate Format Strings
483
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
485
SigScheme fully supports SRFI-48.
487
The 'd' part of '~w,dF' directive is acceptable, but completely ignored on
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output format. Since SigScheme only supports integer currently, number is
489
always formatted as integer even if the 'd' part is specified.
492
================================================================
493
(format "~3F" 3) ==> " 3"
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(format "~3,2F" 3) ==> "3.00"
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================================================================
498
================================================================
499
(format "~3F" 3) ==> " 3"
500
(format "~3,2F" 3) ==> " 3"
501
================================================================
503
Although the reference implementation of SRFI-48 allows directive-less tilde at
504
end of a format string, SigScheme rejects it as an error since it decreases
505
user-code portability, and is confusable due to that the behavior is different
506
to the reference implementation of SRFI-28.
508
.Reference implementation of SRFI-48
509
================================================================
511
(format "a~") ==> "a~"
512
================================================================
515
================================================================
516
(format "~") ==> error
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(format "a~") ==> error
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================================================================
521
SRFI-60 Integer as Bits
522
~~~~~~~~~~~~~~~~~~~~~~~
524
Only following procedures are implemented.
527
* *procedure:* logand n1 ...
528
* *procedure:* bitwise-and n1 ...
529
* *procedure:* logior n1 ...
530
* *procedure:* bitwise-ior n1 ...
531
* *procedure:* logxor n1 ...
532
* *procedure:* bitwise-xor n1 ...
533
* *procedure:* lognot n
534
* *procedure:* bitwise-not n
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* *procedure:* bitwise-if mask n0 n1
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* *procedure:* bitwise-merge mask n0 n1
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* *procedure:* logtest j k
538
* *procedure:* any-bits-set? j k
540
And the others listed below are not.
543
* *procedure:* logcount n
544
* *procedure:* bit-count n
545
* *procedure:* integer-length n
546
* *procedure:* log2-binary-factors n
547
* *procedure:* first-set-bit n
550
* *procedure:* logbit? index n
551
* *procedure:* bit-set? index n
552
* *procedure:* copy-bit index from bit
555
* *procedure:* bit-field n start end
556
* *procedure:* copy-bit-field to from start end
557
* *procedure:* ash n count
558
* *procedure:* arithmetic-shift n count
559
* *procedure:* rotate-bit-field n count start end
560
* *procedure:* reverse-bit-field n start end
563
* *procedure:* integer->list k len
564
* *procedure:* integer->list k
565
* *procedure:* list->integer list
566
* *procedure:* booleans->integer bool1 ...
568
SRFI-75 R6RS Unicode data
569
~~~~~~~~~~~~~~~~~~~~~~~~~
571
SRFI-75 is partially implemented. But since SRFI-75 had already been obsoleted,
572
it is not validated deeply. It will be replaced with stable R6RS implementation
573
once the specifications have been stabilized
575
Current SRFI-75 status
576
^^^^^^^^^^^^^^^^^^^^^^
578
- Supports Unicode character literals such as #\λ
579
- Supports #xXX, #\uXXXX and #\UXXXXXXXX literals
580
- Supports Unicode identifiers (lacks character category validation)
581
- Supports all named chars such as #\backspace, #\esc, and #\nul
582
- Quoted-symbol by vertical bar (such as '|-symbol|) is not supported
587
- Remove #\uXXXX and #\UXXXXXXXX literals
588
- Support variable-length #\xXX literal
589
- Support character category validation for identifiers
590
- Disable #\newline on R6RS-compatible mode
591
- Confirm symbol escape syntax (not defined in R6RS yet)
597
FIXME: describe them.
601
- let and let* bindings
added
removed
sigscheme/doc/spec.txt
