Predicates and lex/yacc?
Predicates and lex/yacc?
- Subject: Predicates and lex/yacc?
- From: Nicholas Crosbie <email@hidden>
- Date: Fri, 25 Nov 2005 11:11:46 +1100 (EST)
I'm trying to set up an XCode project to evaluate
expressions. I thought of using
predicates but I'm not sure that predicates are
suitable for cases where all of the
following are free to change (naturally with certain
limits):
variable name, operator, and length/complexity of
expression
e.g. result 1 = e1 AND e2 NOT (k4 OR k6) ;
result 2 = (e1 OR e3) AND (e2 ORe7) NOT ((k4 OR e6)
AND (k5 AND p7)) ;
***Please speak up if you think this can be handled
through predicates (and how).***
My current approach is to implement a lex/yacc parser
to generate the Cocoa code.
I'm using "MathPaper" (from Garfinkel & Mahoney...
Building Cocoa Applications) as my test bed.
My steps thus far:
1. changed .l and .y files to .lm and .ym,
respectively.
2. added a printf statement to the rules.ym file
(builds
and runs)
3. tried replacing the printf with an NSLog statement
i.e.
hello { printf ( "world"); } /* works */
hello { NSLog (@ "world"); } /* does not work */
Errors include:
JamToolExecution Evaluator (1 error)
......../jam failed with exit code 1
Undefined symbols:
objc_class_name_NSConstantString
_NSLog
__NSConstantStringClassReference
Mathpaper has two targets. Do I need to compile the
lex/yacc
target (called "evaluator") on the command line and
then import this and the .lm and .ym files into XCode
without
specifying a target (I have heard that by not
specifying a target
for the lex and yacc files, XCode won't process them
and
incorrectly assume that they are generating pure ANSI
C code)?
Some other problem(s)?
Note that the method that receives the text back from
the
lex/yacc evaluator includes the following:
str = [ [NSString alloc] initWithData:data
encoding:NSASCIIStringEncoding] ;
Since I'm trying to receive an output from NSLog, I
tried
str = [ [NSString alloc] initWithData:data
encoding: NSUnicodeStringEncoding] ;
(i.e. replaced NSASCIIStringEncoding with
NSUnicodeStringEncoding)
I still get the same complaints about undefined
symbols.
- NDC
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