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dexp.inc
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1991-02-14
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* DEXP.INC
*
* Here's an advanced function that demonstrates the use
* of SNOBOL4's CODE function.
*
* Program structuring would be enhanced if there were a simple
* way to make one line function definitions, rather than coding
* a DEFINE call and a goto around the function body. Function
* DEXP allows these one line definitions. A typical call:
* DEXP('AVERAGE(X,Y) = (X + Y) / 2')
* You can even have multistatement definitions. This call defines
* function SIGN(X) that returns 1 if X is positive, -1 if negative,
* and null if X = 0:
* DEXP('SIGN(X) = GT(X,0) 1 ; SIGN = LT(X,0) -1 ;')
*
* This is one of the many programs and functions from
* "Algorithms in SNOBOL4," by James F. Gimpel.
*
DEFINE('DEXP(PROTO)NAME,ARGS') :(DEXP_END)
* Remove leading blanks, get function name and remove argument list.
DEXP PROTO POS(0) SPAN(' ') =
PROTO BREAK('(') . NAME BAL . ARGS = NAME
* Build the code for the function body, then define it.
CODE(NAME ' ' PROTO ' :S(RETURN)F(FRETURN)')
DEFINE(NAME ARGS) :(RETURN)
DEXP_END