phrep

Phrep includes a simple expression evaluator for #if and #elif directives. It allows for most common operations:

• Arithmetic

  #if 7 / 2 - 5 + 2.5
  

• Comparison

  #if 12 > 3
  

• Constant substitution and tests

  #if CONST > 2.0.0-beta
  

• Regex comparisons (case-insensitive)

  #if !(VER =~ beta)
  

• Alternatives of course

  #if X>0 || Y && Z<0
  

• Constant checks via defined() function

  #if defined(WHATEVER)
  

  Works basically just like #ifdef. There's also a pragma(..) function to look up current processing options.

• And allows to use a few elected PHP functions:

  #if is_int(strpos(abc, b))
  

  Simple file checks even:

  #if file_exists("lib/scope.php")
  

  One can also use strpos, stripos, strstr, stristr, is_int, is_float, is_numeric, max, min, function_exists, and class_exists.

• Invalid expressions:

  #if (1 + - / 0)
  

  Will obviously fail. In the default mode, this will simply skip the condition as falsy (with a warning). In the -W or #pragma(fail=1) mode, it'll however abort further preprocessing.

The expression evaluation is mostly careless with types.

• It usually expands both literal CONST_NAMES as well as string-quoted "CONST_NAMES" eagerly.

• Even numbers may be quoted "1" + "2" == "3". (Which suits the most common use cases though.)

• And it does all comparisions under the presumption they could be version numbers. For example 1.2 > 2.3 is a version comparison, as is "PKG_VERSION" >= 2.0.0. (Relying on PHPs version_compare internally. Though could switch to plain float fallbacks later..)

• Only function names and operators must be noted literally (defined, not "defined" as string).

It's somewhat of an gimmick anyway. You don't commonly need a lot of conditions to control a build/preprocessing run (#ifdef often suffices).

The MacroExpression handler is mainly there for some crude compatibility with CPP and preprocess.py. Converting expressions into PHP evaluable code would just have been more work. Probably.