a chatgpt c port of my java math thingy, i did not even read this and i won't until i learn c, works though i tested it!

checkFunction.c

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>

#define MAX_EXPR_LEN 1024

// Helper functions for parsing
int isOperator(char c) {
    return c == '+' || c == '-' || c == '*' || c == '/' || c == '^';
}

// Function to apply basic operations
double applyOperation(double a, double b, char op) {
    switch (op) {
        case '+': return a + b;
        case '-': return a - b;
        case '*': return a * b;
        case '/': return b != 0 ? a / b : 0; // Avoid division by zero
        case '^': return pow(a, b);
        default: return 0;
    }
}

// Function to evaluate an expression recursively
double evaluate(const char *expr, double x, int *pos) {
    double result = 0;
    char op = '+';
    double current = 0;

    while (expr[*pos] != '\0') {
        char c = expr[*pos];

        if (isdigit(c) || c == '.') {
            // Parse a number
            char numberBuffer[MAX_EXPR_LEN];
            int numLen = 0;

            while (isdigit(expr[*pos]) || expr[*pos] == '.') {
                numberBuffer[numLen++] = expr[*pos];
                (*pos)++;
            }
            numberBuffer[numLen] = '\0';

            current = atof(numberBuffer);

            // Go back one position as we will increment after this loop
            (*pos)--;
        } else if (c == 'x') {
            // Replace variable `x` with its value
            current = x;
        } else if (isOperator(c)) {
            // Apply the previous operation
            result = applyOperation(result, current, op);
            op = c;
            current = 0; // Reset current value for the next number
        } else if (c == '(') {
            // Handle parentheses recursively
            (*pos)++;
            current = evaluate(expr, x, pos);
        } else if (c == ')') {
            // Stop recursion at closing parenthesis
            break;
        }

        (*pos)++;
    }

    // Apply the last pending operation
    result = applyOperation(result, current, op);
    return result;
}

// Wrapper function to evaluate an expression
double parseAndEvaluate(const char *expr, double x) {
    int pos = 0;
    return evaluate(expr, x, &pos);
}

// Function to determine if a function is Even, Odd, or Neither
const char *checkFunctionType(double fx, double fNegX) {
    if (fabs(fx - fNegX) < 1e-6) { // f(x) ≈ f(-x), Even
        return "Even";
    } else if (fabs(fx + fNegX) < 1e-6) { // f(x) ≈ -f(-x), Odd
        return "Odd";
    } else {
        return "Neither";
    }
}

// Main program
int main() {
    char input[MAX_EXPR_LEN];
    double x;

    printf("Enter your function f(x) = ");
    fgets(input, sizeof(input), stdin);
    input[strcspn(input, "\n")] = '\0'; // Remove newline character

    if (strcmp(input, "exit") == 0) {
        return 0;
    }

    printf("Enter a value for x to test the function: ");
    scanf("%lf", &x);

    // Evaluate f(x) and f(-x)
    double fx = parseAndEvaluate(input, x);
    double fNegX = parseAndEvaluate(input, -x);

    // Print results
    printf("\nTesting f(x) = %s\n", input);
    printf("f(%.2f) = %.2f\n", x, fx);
    printf("f(%.2f) = %.2f\n", -x, fNegX);

    // Determine and display the function type
    const char *functionType = checkFunctionType(fx, fNegX);
    printf("Function type: %s\n", functionType);

    return 0;
}

(has some logic errors but its chatgpt code), do not use this