stack.c

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

stack createEmptyStack()
{
    stack s;
    s.header=malloc(sizeof(struct stackNode));
    s.header->dlvl=-1;
    s.header->v=0;
    s.header->next=NULL;
    return s;
}

// push a variable to the stack with its decision level
void push(stack s, Variable v, int dlevel)
{
    dvar node=malloc(sizeof(struct stackNode));
    node->next=s.header->next;
    node->v=v;
    node->dlvl=dlevel;
    s.header->next=node;
}
// pop a variable from the stack
int pop(stack s)
{
    dvar temp=s.header->next;
    int var=temp->v;
    s.header->next=temp->next;
    free(temp);
    return var;
}

// get the decision level of the top variable in the stack
int getTop(stack s)
{
    if (s.header->next==NULL)
        return -1;
    return s.header->next->dlvl;
}