This makes no sense at all to me

[AndroidZ]

I can see no syntactical or logical errors. Everything compiles fine. The problem?
My evaluate function won't evaluate any commands, except for "exit" which exits the program as it should. Even if I just make the case for "push" or "commands" a single cout line, it doesn't work. I'm baffled here. Does anyone have any idea what the problem is? It was working earlier, but now it's not, and I don't know why.

intstack.h

#pragma once

#include <stdlib.h>
class IntStack
{
    //int DEFAULT_current_element;
    int current_element;
    int* st_arr;
public:
    const static int DEFAULT_STACK_CAPACITY = 100;
    size_t stack_capacity;
    //default constructor
    IntStack() : /*DEFAULT_STACK_CAPACITY(100),*/ st_arr(new int [DEFAULT_STACK_CAPACITY]), stack_capacity(DEFAULT_STACK_CAPACITY), current_element(0)
    {
    }
    //overloaded constructor
    IntStack(int n) : stack_capacity(n), st_arr(new int [DEFAULT_STACK_CAPACITY]), current_element(0)
    {
    }
    //destructor
	~IntStack() {delete [] st_arr;}
    void reset();
    void push(int n);
    void push(int a[], size_t array_size);
    int pop();
    void pop(int a[], size_t n);
    int top();
    size_t size();
    size_t capacity();
    void double_capacity();
    bool is_full();
    bool is_empty();
    //void evaluate(std::string com);
    friend IntStack print_stack(IntStack* pstack);
};

main.cpp

#include <iostream>
#include <stdlib.h>
#include <string>
#include <cassert>
#include "intstack.h"

using namespace std;

void command_list();
void evaluate(string com, IntStack* st);
IntStack create_stack(char capans, int cap);
int main()
{
    string command;
    //int st_num = 0;

    char capans = 'y';
    int cap;
    cout << "Welcome to the stack program. To begin with, a stack must be created. \n";
    cout << "Would you like to use the default capacity of 100? y/n \n";
    cin >> capans;
    if (capans == 'n'){
        cout << "Enter capacity: \n";
        cin >> cap;
    }
    IntStack st = create_stack(capans, cap);

    int arr_size;
    cout << "Now an array of integers needs to be created. How many integers will this array have? \n";
    cin >> arr_size;
    int arr[arr_size];
    int el;
    for (int i = 0; i < arr_size; i++){
        cout << "Enter element " << i << " of the array \n";
        cin >> el;
        arr[i] = el;
    }

    cout << "Here are your command choices: \n";
    cout << "push     //to push ints to stack \n";
    cout << "pop      //to pop off elements \n";
    cout << "top      //to get top element of stack \n";
    cout << "print    //to print a stack \n";
    cout << "size     //to get the size of a stack \n";
    cout << "capacity //to see the capacity fo a stack \n";
    cout << "reset    //reset stack \n";
    cout << "commands //to display this command list \n";
    cout << "exit     //to exit the program \n\n";
    //int result;
    while(1==1){
        cout << "> ";
        cin >> command;
        evaluate(command, &st);


    }
    return 0;
}

intstack.cpp

#include <string>
#include "intstack.h"
#include <iostream>

using namespace std;

IntStack print_stack(IntStack* pstack){
    for (int i = 0; i < pstack->current_element; i++){
        cout << pstack->st_arr[i] << "\n";
    }
}

int IntStack::top(){
    current_element--;
    int temp = current_element;
    current_element++;
    return st_arr[temp];
}

size_t IntStack::size(){
    return current_element;
}

size_t IntStack::capacity(){
    return stack_capacity;
}

void IntStack::reset(){
    for (int i = 0; i < stack_capacity; i++){
        st_arr[i] = NULL;
    }
    current_element = 0;
}

void IntStack::push(int n){
    if (current_element == stack_capacity){
        cout << "Stack full... doubling capacity \n";
        double_capacity();
    }
    st_arr[current_element] = n;
    current_element++;
}

void IntStack::push( int arr[], size_t array_size ){
    for (int i = 0; i < array_size; i++){
        if (current_element == stack_capacity){
            double_capacity();
        }
        push(arr[i]);
    }
}

int IntStack::pop(){
    if (current_element == 0){
        cerr << "STACK EMPTY\n";
    }
    --current_element;
    int temp = st_arr[current_element];
    st_arr[current_element] = NULL;
    return temp;
}

void IntStack::pop( int a[], size_t n ){
    if (current_element > 0)
        current_element--;
    for (int idx = 0; idx < n; idx++){
        if (current_element == 0){
            cerr << "STACK EMPTY\n";
        }
        a[idx] = st_arr[current_element];
        st_arr[current_element] = NULL;
        if(current_element>0)
            current_element--;
    }
    //cout << "after popping, i is " << i << "\n"; //DB
}

int* allocate(int num);
void deallocate(int* old);

void IntStack::double_capacity(){
    int* new_mem = allocate(stack_capacity * 2);

    for (int i = 0; i < current_element; i++){
        new_mem[i] = st_arr[i];
    }
    deallocate(st_arr);
    st_arr = new_mem;
    stack_capacity *= 2;
}

int* allocate(int num){
    int* new_mem = new int[num];
    return new_mem;
}

void deallocate(int* old){
    delete[] old;
}

bool IntStack::is_full(){
    if(current_element == 100)
        return true;
    else
        return false;
}

bool IntStack::is_empty(){
    if(current_element != 0)
        return false;
    else
        return true;
}

//-------------------------
//---Interface Functions---
//-------------------------

void command_list(){
    cout << "Here are your command choices: \n";
    cout << "push     //to push ints to stack \n";
    cout << "pop      //to pop off elements \n";
    cout << "top      //to get top element of stack \n";
    cout << "print    //to print a stack \n";
    cout << "size     //to get the size of a stack \n";
    cout << "capacity //to see the capacity fo a stack \n";
    cout << "reset    //reset stack \n";
    cout << "commands //to display this command list \n";
    cout << "exit     //to exit the program \n\n";
}

void evaluate(string com, IntStack* st_ ){
    int c;

    if (com == "push")    { c = 0; }
    if (com == "pop")     { c = 1; }
    if (com == "top")     { c = 2; }
    if (com == "print")   { c = 3; }
    if (com == "size")    { c = 4; }
    if (com == "capacity"){ c = 5; }
    if (com == "reset")   { c = 6; }
    if (com == "commands"){ c = 7; }
    if (com == "exit")    { c = 8; }
    else                  { c = 9; }

    //IntStack st = *st_;
    switch (c)
    {
        case 0:
            int x;
            cout << "Enter int: \n";
            cin >> x;
            st_->push(x);
            break;
        case 1:
            cout << "pop";
            break;
        case 2:
            exit(1);
            break;
        case 3:
            //print_stack(&st);
            break;
        case 4:
            break;
        case 5:
            break;
        case 6:
            break;
        case 7:
            command_list();
            break;
        case 8:
            exit(1);
        case 9:
            break;
    }
}

IntStack create_stack(char capans, int cap ){
    if (capans == 'y'){
        IntStack st;
        return st;
    }
    if (capans == 'n'){
        IntStack st(cap);
        return st;
    }
}

[helios]

Line 144 of intstack.cpp: this block runs when com!="exit", not when it is different to each of the other conditions that were just evaluated, thus it always overwrites the contents of c except when com=="exit".
For example, if com=="size", the block on line 139 will run, correctly setting c to 4, and then the one on line 144 will run, setting it to 9.

[AndroidZ]

Aha! Much appreciated.