'Multipurpose' linked list implementation in pure C

Question

This is not exactly a technical question, since I know C kind of enough to do the things I need to (I mean, in terms of not \'letting the language get in your way\'), so thi

Answer 1

This is a good problem. There are two solutions I like:

• Dave Hanson's C Interfaces and Implementations uses a list of void * pointers, which is good enough for me.

• For my students, I wrote an awk script to generate type-specific list functions. Compared to preprocessor macros, it requires an extra build step, but the operation of the system is much more transparent to programmers without a lot of experience. And it really helps make the case for parametric polymorphism, which they see later in their curriculum.

  Here's what one set of functions looks like:

  int      lengthEL (Explist *l);
  Exp*     nthEL    (Explist *l, unsigned n);
  Explist *mkEL     (Exp *hd, Explist *tl);
  

  The awk script is a 150-line horror; it searches C code for typedefs and generates a set of list functions for each one. It's very old; I could probably do better now :-)

I wouldn't give a list of unions the time of day (or space on my hard drive). It's not safe, and it's not extensible, so you may as well just use void * and be done with it.