c-generics

❓ What is this repository about

C language does not support generics and templates. This repository introduces one of the possible (and convenient) ways to implement generic containers using C preprocessing macros.

🧰 How to implement custom generic data structure

1. Header file with any generic container implementation must include instantiation.h file, which allows programmer to use simpler and standardized typed container initialization.
2. Container instantiation should be implemented in implicit and explicit ways. Implicit instantiation is a #define directive that accepts arguments such as structure name, type (data type that structure will contain), arguments (optional instantiation parametres). This instantiation will explicitly create a template of data structure of the given type. This define name must have the form _do_instantiate_<struct_name>.
3. Explicit instantiation is a convenient way for programmer to create a template of data structure. This #define may have the form instantiate_<struct_name>(type) and substitute INSTANTIATION_INSTANTIATE_CONTAINER(<struct_name>, <type>, ).
4. To create an instance of previously described container header file must implement directive #define <struct_name>(<type>) that declares a type named INSTANTIATION_GET_CONTAINER_NAME(<struct_name>, <type>).
5. Container methods can be implemented in different ways (either #define or regular functions). It may depend on container type or your ideology :)

You can check implementation details in our examples of stack implementation and vector implementation.

🚩 Usage

Example for stack

Code

#include <stdio.h>
#include "stack.h"

typedef struct box {
    int weight;
    char *content;
} box;

instantiate_stack(box);

int main() {
    stack(box) storage = init_stack();

    box toolbox = {.weight = 5, .content = "tools"};
    box clothes = {.weight = 3, .content = "t-shirts, pants"};
    box paper = {.weight = 1, .content = "sheets of paper"};

    stack_push(&storage, toolbox);
    stack_push(&storage, clothes);
    stack_push(&storage, paper);

    printf("%lld boxes in storage\n", stack_size(&storage));
    while (!stack_empty(&storage)) {
        printf("Box with %s and weight %d kg.\n", stack_top(&storage).content, stack_top(&storage).weight);
        stack_pop(&storage);
    }
}

Output

3 boxes in storage
Box with sheets of paper and weight 1 kg.
Box with t-shirts, pants and weight 3 kg.
Box with tools and weight 5 kg.

Example for vector

Code

#include <stdio.h>
#include "vector.h"

instantiate_vector((char)(*));

int main() {
    vector((char)(*)) shopping_list = init_vector();

    vector_push(&shopping_list, "Potatoes");
    vector_push(&shopping_list, "Carrots");
    vector_push(&shopping_list, "Meat");
    vector_pop(&shopping_list);
    vector_push(&shopping_list, "Milk");

    printf("%d products in list\n", vector_size(&shopping_list));
    for (int i = 0; i < vector_size(&shopping_list); i++) {
        printf("%d. %s\n", i + 1, shopping_list[i]);
    }

    vector_destroy(&shopping_list);
    return 0;
}

Output

3 products in list
1. Potatoes
2. Carrots
3. Milk

🌟 I express my gratitude to purplesyringa for her great contribution!