---
title: "generics"
type: concept
related: [Casting, Generic]
source: https://www.jemoka.com/posts/kbhgeneric/
confidence: high
status: active
---

We don&rsquo;t want to write the same thing many times; generics minimizes code duplication. Therefore, generics!
Let&rsquo;s implement a simple swap function:
void swap_ptr_values(void *data1ptr, void *data2ptr, size_t datasize) { } helper functions memcpy Copy datasize bytes worth of memory in the second argument into the first argument. The two arguments CANNOT OVERLAP otherwise, you risk UB.
void *memcpy(void *dest, void *src, size_t nbytes) memmove Its memcpy, but it works with overlapping data, and is slower.
void *memove(void *dest, void *src, size_t nbytes) pointer arithmetic with generics Unfortunately, given that we don&rsquo;t know how big a void * pointer is, we can&rsquo;t do pointer arithmetic against it because it still doesn&rsquo;t know how big the pointer is. You can&rsquo;t just add/subtract numbers to char *.
So, we actually have to do pointer arithmetic by casting the pointer to a char* which will make pointer arithmetic work at the one-byte level.
void *return_sixth_elem(void *arr) { return (char *)arr + 5; } higher order functions We can pass a function as a parameter.
bool (*function_name)(int, int)
