rxi/vec - a simple C vector library

C provides arrays, but these do less than most other languages’ array structures. For instance, if you want to push a new element onto the end of your array, you must go through the work of resizing it with realloc to make room for the new element. For this, you need to keep track of the array length separately. Then to avoid constant reallocation you keep a separate length and capacity. Soon you’ve written a vector library.

Instead, you can use someone else’s vector library. I like rxi/vec. Here’s an example of using it. Installation:

$ brew install clib
$ clib install rxi/vec
$ find .

Example program:

#include <stdio.h>
#include "./deps/vec/vec.h"
typedef vec_t(char*) vec_string_t;
void print_vec(vec_string_t * strings) {
  size_t i; char * string;
  vec_foreach(strings, string, i) {
    printf("strings[%zu] = \"%s\"\n", i, string);
int main() {
  vec_string_t strings;
  vec_init(&strings);  // memset(&strings, 0, sizeof(strings));
  vec_push(&strings, "hello");
  vec_push(&strings, "world");
  char* world = vec_pop(&strings);
  printf("popped %s\n", world);
  return 0;

Running it gives:

$ clang main.c deps/vec/vec.c
$ ./a.out
strings[0] = "hello"
strings[1] = "world"
popped world
strings[0] = "hello"

In a future post, I’ll show how rxi/vec is implemented.

I wrote this because I felt like it. This post is my own, and not associated with my employer.

Jim. Friends. Vidrio.