Reserved Words in C [pdf] | Hacker News Reader

Reserved Words in C [pdf]

bezem.de

Two interesting ones that caught my eye:

"entry". It was a keyword only in Pre-K&R C. I wonder what it did (and I don't have the time to dig just right now).

"I". It's a "secondary" keyword (basically an alternative spelling of some other keyword according to the legend), but only since C11, but not in any C++ dialects. I wonder what it's an alternative spelling for. This one is hard to google, or even just search for in the spec...

I don't think that "entry" was ever implemented, but the intent was to support something like the ENTRY statement of Fortran.

https://en.cppreference.com/w/c/numeric/complex/imaginary

  #include <complex.h>
  ...
  double imaginary i = -2.0*I; // pure imaginary
  double f = 1.0; // pure real
  double complex z = f + i; // complex number

from gcc's complex.h:

  #ifdef __GNUC__
  #if __STDC_VERSION__ < 199901
  #define _Complex        __complex__
  #endif
  #define _Complex_I      ((float _Complex)1.0i)
  #endif

  #ifdef __generic
  _Static_assert(__generic(_Complex_I, float _Complex, 1, 0),
      "_Complex_I must be of type float _Complex");
  #endif

  #define complex         _Complex
  #define I               _Complex_I

Ah. I even entertained the fact that it may be for complex numbers, but... honestly didn't know C added support for that! This despite using complex numbers a lot, just not in C so far. I always assumed I would have to use an external library.

Reserved words in Fortran and PL/1:

friend!?

https://en.cppreference.com/w/cpp/language/friend

Under "Reserved words in C" is "(and C++)" making the HN title a bit misleading.

"friend" is a C++ keyword but not one in C.

There's an old joke about C++ programmers, exposing private members, and friends that I probably can't repeat here.

Only friends can access privates

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