calculator.c

//header files
#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<string.h>
#include <math.h>

//global variables
#define MAX_STACK 1000
float numbers[MAX_STACK];
int tn = -1, to = -1;
char op[MAX_STACK];
//function to push digits
void push_num(float n)
{
    numbers[++tn] = n;
}
//function to push operators
void push_op(char ch)
{
    op[++to] = ch;
}
//function to pop digits
float pop_num()
{
    return numbers[tn--];
}
//function to pop operators
char pop_op()
{
    return op[to--];
}

bool is_unary(char s)
{
    switch (s)
    {
        case 'S': // Trignometric function
            return true;
        case 'T':
            return true;
        case 'C':
            return true;
        case 'O': //COt
            return true;
        case 'E': // SEC
            return true;
        case 'I': // SIN
            return true;
    }

    return false;

}

//evaluating the expression
float infix_eval(float numbers[MAX_STACK], char op[MAX_STACK])
{
    float x, y;
    char ope;
    
    //taking the operators between them
    ope = pop_op();



    //taking first two operands
    x = pop_num();
    if (!is_unary(ope))
    {
        y = pop_num();
    }
        //executing the operation
    switch (ope)
    {
        case '+':
            return x + y;
        case '-':
            return y - x;
        case '*':
            return x * y;
        case '/':
            if (x == 0)
            {
                printf("\nCan not divide by 0");
                exit(0);
            }
            else
                return y / x;
        case 'S' :
            return sin(x);
        case 'C':
            return cos(x);
        case 'T':
            return tan(x);
        case 'E':
            return 1/cos(x);
        case 'I':
            return 1/sin(x);
        case 'O':
            return 1/tan(x);
    }
    return 0;
}
//function to check whether the character is an operator or not 
int is_operator(char ch)
{
    return(ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == '^' || ch == 'S' || ch == 'T' || ch == 'C' || ch == 'I' || ch == 'O' || ch == 'E');
}

//the precedence of the operators
int precedence(char c)
{
    switch (c)
    {
        case '+':
            return 1;
        case '-':
            return 1;
        case '*':
            return 2;
        case '/':
            return 2;
        case '^':
            return 3;
        case 'S': // Trignometric function
            return 4;
        case 'T':
            return 4;
        case 'C':
            return 4;
        case 'O': //COt
            return 4;
        case 'E': // SEC
            return 4;
        case 'I': // SIN
            return 4;
    }
    return -1;
}
//function to evaluate an infix expression
float eval(char exp[20])
{
    float num, output;
    int i , r;
    char c;
    for (i = 0; exp[i] != '\0'; i++)
    {
        //taking each character from the expression
        c = exp[i];
        //checking if it is number
        if (isdigit(c) != 0)
        {
            num = 0;
            while (isdigit(c))
            {
                num = num * 10 + (c - '0');
                i++;
                if (i < strlen(exp))
                    c = exp[i];
                else
                    break;
            }
            i--;
            //pushing the number into stack of numbers
            push_num(num);
        }
        else if (c == '(')
        {
            //pushing the operators into the stack
            push_op(c);
        }
        //If we get close bracket, evaluate the entire bracket
        else if (c == ')')
        {
            while (op[to] != '(')
            {
                r = infix_eval(numbers, op);
                //pushing the result back to stack
                push_num(r);
            }
            pop_op();
        }
        // if the current character is operator
        else if (is_operator(c))
        {
            //evaluating the expression
            while (to != -1 && precedence(c) <= precedence(op[to]))
            {
                output = infix_eval(numbers, op);
                //pushing the result back to stack
                push_num(output);
            }
            //pushing the current operator to stack
            push_op(c);
        }
    }
    //if there is any remaining expression, evaluate them
    while (to != -1)
    {
        output = infix_eval(numbers, op);
        //pushing it back to stack
        push_num(output);
    }
    return pop_num();
}

//main function
int main()
{
    char exp[50] = "10*S(10)-5*T(8+7*9)";
    //char exp[50] = "T(1/2)";
    //taking the expression to evaluate
    printf("Enter the infix expression to evaluate: ");
    //scanf("%s",exp);
    //calling the function and printing the reult
    printf("%f", eval(exp));
}