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A. TRANSLATABLE VAXIMA STATEMENTS & EXPRESSIONS
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A substantial subset of all VAXIMA statements and expressions can be
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translated by GENTRAN into semantically equivalent code in the target
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numerical language[9]. This
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[9] It should be noted that call-by-value parameter passing is used in
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VAXIMA, while call-by-address parameter passing is normally used in
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FORTRAN and RATFOR. GENTRAN does not attempt to simulate call-by-value
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passing when generating code.
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appendix is divided into two sections. The first section contains a
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formal definition of all translatable VAXIMA statements and expressions. The
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second section contains examples of several statement types
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translated into FORTRAN, RATFOR and C code.
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A.1. Formal Definition
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This section contains a formal definition of all VAXIMA statements and
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expressions that can be translated by GENTRAN into numerical
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code. First the VAXIMA user level syntax is given, and then the
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LISP level syntax is given.
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Note: Terminals are \fIunderlined\fR.
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\fIeps\fR represents the empty string.
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Preliminary Definitions
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\fIid\fR - an identifier (i.e., atom).
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\fIstring\fR - any number of characters (excluding double quotes)
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enclosed in double quotes.
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Arithmetic Expressions:
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exp ::= \fInumber\fR | var | funcall | \fIabs( \fRexp ) |
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- exp | exp + exp | exp - exp |
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exp * exp | exp / exp | exp ** exp |
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exp' ::= , exp exp' | \fIeps\fR
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exp'' ::= exp exp' | \fIeps\fR
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var ::= \fIid\fR | \fIid [ \fRexp exp' ]
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funcall ::= \fIid( \fRarg' )
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arg ::= exp | logexp | \fIstring\fR
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arg' ::= arg arg' | \fIeps\fR
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arg0 ::= arg | \fIeps\fR
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string0 ::= \fIstring\fR | \fIeps\fR
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id' ::= \fIid\fR id'' | \fIeps\fR
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id'' ::= , \fIid\fR id'' | \fIeps\fR
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logexp ::= \fItrue\fR | \fIfalse\fR | var | funcall |
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exp > exp | exp >= exp | exp = exp |
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exp # exp | exp < exp | exp <= exp |
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\fInot\fR logexp | logexp \fIand\fR logexp |
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logexp \fIor\fR logexp | ( logexp )
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Parentheses are automatically generated when expressions are
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translated which contain operators whose precedence in VAXIMA
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differs from that in the target language. Thus the meaning of
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the original expression is preserved.
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For example, in VAXIMA,
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not a = b and not (a = b)
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are equivalent, whereas in C,
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! a == b and (!a) == b
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are equivalent. Therefore,
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is translated into C code which forces the VAXIMA precedence rules:
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stmt ::= assign | loop | cond | go | call |
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return | iostmt | stmtgp
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stmt' ::= , stmt stmt' | \fIeps\fR
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assign ::= var : exp |
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\fIid : matrix( \fRrow row' )
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row' ::= , row row' | \fIeps\fR
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loop ::= \fIfor\fR var initval nextexp thruexp loopcond \fIdo\fR
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initvar ::= : exp | \fIeps\fR
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nextexp ::= \fIstep\fR exp | \fInext\fR exp | \fIeps\fR
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thruexp ::= \fIthru\fR exp | \fIeps\fR
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loopcond ::= \fIwhile\fR logexp | \fIunless\fR logexp | \fIeps\fR
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cond ::= \fIif\fR logexp \fIthen\fR stmt elsestmt
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elsestmt ::= \fIelse\fR stmt | \fIeps\fR
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go ::= \fIgo( \fRid )
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call ::= \fIid( \fRexp'' )
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return ::= \fIreturn( \fRarg0 )
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iostmt[10] ::= var : \fBreadonly( \fRstring0 ) |
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\fIprint( \fRarg arg' )
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[10] I/O statements cannot be translated into C code.
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stmtgp ::= ( stmt stmt' )[11] |
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\fIblock( \fRstmt stmt' )[12]
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[11] VAXIMA compound statements are translated into (undelimited) statement
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[12] VAXIMA statement blocks are translated into statement \fIgroups\fR
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(delimited by { and }) when RATFOR or C code is being generated. However,
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they are translated into (undelimited) statement \fIsequences\fR when the
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target language is FORTRAN.
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subprog ::= \fIid( \fRid' ) := body ;
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body ::= stmt | exp | logexp
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Preliminary Definitions
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\fIid \fR- an identifier (i.e., atom whose first character is
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\fIstring\fR - an atom whose first character is &.
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Arithmetic Expressions:
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exp ::= \fInumber\fR | var | funcall |
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\fI((mabs) \fRexp) | \fI((mminus) \fRexp) |
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\fI((mplus) \fRexp exp') | \fI((mtimes) \fRexp exp') |
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\fI((mquotient) \fRexp exp) | \fI((mexpt) \fRexp exp)
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exp' ::= exp exp' | \fIeps\fR
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var ::= \fIid\fR | \fI((id) \fRexp exp')
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funcall ::= \fI((id) \fRarg')
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arg ::= exp | logexp | \fIstring\fR
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arg' ::= arg arg' | \fIeps\fR
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arg0 ::= arg | \fIeps\fR
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string0 ::= \fIstring\fR | \fIeps\fR
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id' ::= \fIid \fRid' | \fIeps\fR
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logexp ::= \fIt\fR | \fInil\fR | var | funcall |
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\fI((mgreaterp) \fRexp exp) |
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\fI((mgeqp) \fRexp exp) |
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\fI((mequal) \fRexp exp) |
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\fI((mnotequal)\fR exp exp) |
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\fI((mlessp) \fRexp exp) |
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\fI((mleqp) \fRexp exp) | \fI((mnot) \fRlogexp) |
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\fI((mand) \fRlogexp logexp logexp') |
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\fI((mor) \fRlogexp logexp logexp')
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logexp' ::= logexp logexp' | \fIeps\fR
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stmt ::= assign | loop | condR | go | call |
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return | iostmt | stmtgp
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stmt' ::= stmt stmt' | \fIeps\fR
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assign ::= \fI((msetq) \fRvar exp) |
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\fI((msetq) id (($matrix) \fRrow row'))
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row ::= \fI((mlist) \fRexp exp')
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row' ::= row row' | \fIeps\fR
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loop ::= \fI((mdo) \fRvar initexp stepexp nextexp thruexp
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initexp ::= exp | \fInil\fR
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stepexp ::= exp | \fInil\fR
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nextexp ::= exp | \fInil\fR
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thruexp ::= exp | \fInil\fR
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loopcond ::= logexp | \fInil\fR
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cond ::= \fI((mcond) \fRlogexp stmt \fIt\fR elsestmt)
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elsestmt ::= stmt | \fI$false\fR
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go ::= \fI((mgo) id)\fR
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call ::= \fI((id) \fRexp')
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return ::= \fI((mreturn) \fRarg0)
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iostmt[13] ::= \fI((msetq) \fRvar \fI(($readonly) \fRstring0)) |
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[13] I/O statements cannot be translated into C code.
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\fI(($print) \fRarg arg')
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stmtgp ::= \fI((mprogn) \fRstmt stmt')[14] |
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\fI((mprog) \fRstmt stmt')[15]
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[14] VAXIMA compound statements are translated into (undelimited) statement
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[15] VAXIMA statement blocks are translated into statement groups (delimited
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by { and }) when RATFOR or C code is being generated. However, they are
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translated into (undelimited) statement \fIsequences\fR when the
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target language is FORTRAN.
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subprog ::= \fI((mdefine) ((id) \fRid') body)
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body ::= stmt | exp | logexp
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The following table contains a list of VAXIMA statement types
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that can be translated by GENTRAN. Examples of each statement
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type, along with equivalent FORTRAN, RATFOR and C code, are given.
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share/contrib/gentran/man/appA1.ms
