How to fix expected 'const char *' but argument is of type 'char **` while using strcmp() in a function

Question

It's supposed to be a function that finds the sum, difference etc of a two numbers depending on the chosen operator but when I use strcmp() to check the chosen operator I get the error expected 'const char *' but argument is of type 'char **'

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include <string.h>

int calc(int ran1,int ran2,char op){
    if(strcmp(op, "+")==0){
        return ran1+ran2;
    }
    if(strcmp(op, "-")==0){
        return ran1-ran2;
    if(strcmp(op, "*")==0){
        return ran1*ran2;
    }
    if(strcmp(op, "/")==0){
        return ran1/ran2;
    }
    }
}
int main(){
    int ran1=25;
    int ran2=5;
    char op="+";
    printf("%d", calc(ran1, ran2, op));

}

Answer 1

It seems that this error message

expected 'const char *' but argument is of type 'char **'

does not correspond to the presented code because neither expression of the type char ** is used in the program.

Also there is a logical error in the function due to the invalid placement of braces

int calc(int ran1,int ran2,char op){
    if(strcmp(op, "+")==0){
        return ran1+ran2;
    }

    if(strcmp(op, "-")==0){
        return ran1-ran2;
        if(strcmp(op, "*")==0){
            return ran1*ran2;
        }
        if(strcmp(op, "/")==0){
            return ran1/ran2;
        }
    }
}

Nevertheless for starters this initialization

char op="+";

is incorrect. It seems you mean

char op = '+';

That is you need to initialize the object op of the type char with the integer character constant '+' instead of the string literal "+".

As the parameter op has the type char

int calc(int ran1,int ran2,char op){

then it may not be used in a call of strcmp like

 if(strcmp(op, "+")==0){

It is enough to use just the equality operator == in this and other similar if statements like

if ( op == '+' )

Take into account that instead of the if statements you could use a switch statement. For example

switch ( op )
{
case '+':
    //...
case '-':
    //...
}