4 ms·

Oof, all the macros are broken: #define is_space(x) (x == ' ' || x == '\n') #define is_parens(x) (x == '(' || x == ')') Should be #define is_spa

• geofft 9y ago
  That still evaluates x twice, which can also be a source of bugs. I usually take one of two approaches: either decide that this is a weekend hack and using the macros whenever the expansion isn't obvious in my head is a sign of too much complexity, or use this GCC extension: #define is_space(x) ({ typeof(x) y = x; y == ' ' || y = '\n'; }) (Or in this case, turn it into an actual function and let the compiler figure out optimization.)
  • kindfellow92 9y ago
    GCC extensions make my brain hurt :( Should just use C++ at that point: template<class T> bool is_space(const T & x) { return x == ‘ ‘ || x == ‘\n’; }
    • pjmlp 9y ago
      Even better if you make it: template<class T> constexpr bool is_space(const T & x) { return x == ' ' || x == '\n'; } Debuggable, type safe and same performance as straight C code.
      • IvanVergiliev 9y ago
        And throw an `inline` in there just to be more likely to end up with something macro-like.
        • atilaneves 9y ago
          `constexpr` is implicitly `inline`: http://en.cppreference.com/w/cpp/language/inline http://en.cppreference.com/w/cpp/language/inline
          • gpderetta 9y ago
            orthogonally, templates are also implicitly inline. Then again, inline does not mean what most people think.
        • kindfellow92 9y ago
          “inline” is more about linkage than about actual inlining. The compiler will in-line regardless of that attribute.
      • kindfellow92 9y ago
        Constexpr is not necessary. Only required if you want to ensure that a variable is initialized with a pre-computed value. The compiler will optimize in either case if it can, regardless of the constexpr attribute.
        • pjmlp 9y ago
          > Only required if you want to ensure that a variable is initialized with a pre-computed value Yep.
    • klmr 9y ago
      The function can be trivially implemented in C, since you don’t need a generic input argument type. No idea why OP chose macros in the first place.
• unwind 9y ago
  I'd argue that is_space() should be isspace(), the standard from <ctypes.h>. Pretty sure it wouldn't make the semantics of the language worse, but it's one less wheel re-invented and makes the code a smidgen easier to read since there's one less concept to learn in it. Also one less thing to debug ...
  • unwind 9y ago
    Heh. Make that <ctype.h>, of course. D'oh. :)