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Re: What stage should entities be resolved?

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On Thursday, March 17, 2022 at 11:41:47 AM UTC-7, Roger L Costello wrote:

(snip)

> For instance, as I understand it a C preprocessor goes through a C program and replaces macros. With this:

> #define PI 3.14

> the preprocessor will convert this:

> area = PI * radius * radius;

> to this:

> area = 3.14 * radius * radius;

> But if PI is inside a quoted string:

> "Today is PI day"

(You missed by a few days.)

> then the preprocessor does not replace PI.

As well as I know it, the early preprocessor, used by K&R C, did
substitute in strings. The current standard version does not, but some
versions have the --traditional option which might allow it.

It is not unusual to use the C preprocessor with --traditional for
Fortran programs, and some compilers will automate this. Some of the
processing done by the current C standard version messes up Fortran
programs too much.

Note, though, that the C preprocessor is pretty good at ignoring
almost anything, including mismatched quotes, between

#if 0

and the matching

#endif

The text doesn't need to look much like C at all, and can even have
mismatched quotes. It does have to properly process nested #if though.

The PL/I preprocessor isn't quite as forgiving.

At least in the early compilers, like early C compilers, it was
implemented as a separate pass, with intermediate disk file. I suspect
you can't put quite as much garbage between

%IF 0 %THEN %DO

and

%END

and especially likely not unmatched quotes.  (PL/I uses apostrophes
for character constants, in both the language itself and the preprocessor.)

Java, on the other hand, does not have a preprocessor.  The compiler is
supposed to know enough not to compile statements between

if(0) {

and

}

but I suspect that they need to look a lot like Java statements.
(You can also use a static final variable in such an if statement,
which the compiler knows how to evaluate at compile time.)

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Thread

What stage should entities be resolved? Lexical analysis stage? Syntax analysis stage? Semantic analysis stage? Roger L Costello <costello@mitre.org> - 2022-03-09 17:22 +0000
  Re: What stage should entities be resolved? Lexical analysis stage? Syntax analysis stage? Semantic analysis stage? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2022-03-10 09:48 +0100
    Re: What stage should entities be resolved? Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2022-03-12 14:11 +0200
      Re: What stage should entities be resolved? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2022-03-14 19:43 +0100
    Re: What stage should entities be resolved? Roger L Costello <costello@mitre.org> - 2022-03-15 11:49 +0000
      Re: What stage should entities be resolved? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2022-03-18 00:31 +0100
      Re: What stage should entities be resolved? gah4 <gah4@u.washington.edu> - 2022-03-17 17:06 -0700
      Re: What stage should entities be resolved? Kaz Kylheku <480-992-1380@kylheku.com> - 2022-03-18 17:50 +0000
        Re: What stage should entities be resolved? gah4 <gah4@u.washington.edu> - 2022-03-18 14:08 -0700
        Re: What stage should entities be resolved? Martin Ward <martin@gkc.org.uk> - 2022-03-19 18:17 +0000
      Re: What stage should entities be resolved? "matt.ti...@gmail.com" <matt.timmermans@gmail.com> - 2022-03-20 07:32 -0700
  RE: What stage should entities be resolved? Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2022-03-10 12:54 +0200
  Re: What stage should entities be resolved? Lexical analysis stage? Syntax analysis stage? Semantic analysis stage? matt.timmermans@gmail.com - 2022-03-12 05:12 -0800

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