IsDouble function prototype syntax error & warning (data definition has no type or storage class)

Question

Been playing around with c trying to parse a csv file.

Right now I'm trying to implement a function to check where or not a string is only a double so I can then convert it. However I'm having some problems in the .h file getting "syntax error before bool" and "data definition has no type or storage class"

#ifndef MSGR_H
#define MSGR_H

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

typedef struct Entry 
{
    char *str;
    int iVal;
} Entry;

int NumRows(char fileName[]);
int NumColumns(char fileName[]);
void TokenizeLine(int x; int y; char currentLineStr[], Entry eTable[x][y], int yIndex, int x, int y);
*** bool IsDouble(const char *str);*** (problem is supposedly here)
#endif

Below is the function itself.

bool IsDouble(const char *str)
{
 char *endPtr = 0;
 bool flag = true;
 strtod(str, &endPtr);

 if(*endPtr != '\0' || endPtr == str);
            flag = false;
 return flag;
}

Appreciate any and all input.

Answer 1

There is no bool in C unless you use at least C99 and include <stdbool.h>.

Common practice: return int, 0 evaluates to false, anything else (normally 1) to true when used as a boolean.

Code:

int IsDouble(const char *str)
{
    char *endPtr = 0;
    strtod(str, &endPtr);

    if(*endPtr != '\0' || endPtr == str)
    {
        return 0;
    }
    return 1;
}

(There was also a superfluous semicolon ...)