stack.h

Jonas Altrock ew20b126@technikum-wien.at

The whole source file stack.h.
To the implementation file stack.c.

Back to postfix.c

/* */

This is a so-called include guard. The preprocessor excludes the whole section of code from ifndef to endif if this file is included more than once in one compilation unit, and the constant STACK_H has already been defined. For this exercise it is not necessary, but good practice for creating library header files.

#ifndef STACK_H
#define STACK_H

This is an “opaque struct handle”, meaning that we have a typedef for using the struct type from the outside, but the fields are not known to code that only includes the stack.h header file.

It hides that it’s a pointer type, but that’s ok for a handle. We could change the semantics of this handle and make it a non-pointer type, and the users of this code would not have to change anything.

typedef struct stack* stack_handle_t;

Create a stack (on the heap).

stack_handle_t stack_create();

Free the memory allocated by stack_create.

void stack_destroy(stack_handle_t);

Peek at the top value on stack.

int stack_top(stack_handle_t);

Push a value to the stack.

void stack_push(stack_handle_t, int);

Pop the top value off the stack.

int stack_pop(stack_handle_t);

Get the height of the stack.

int stack_len(stack_handle_t);

#endif