get_double - prompt a user for a double

get_double - prompts user for a line of text from stdin and returns the equivalent double


#include <cs50.h>
double get_double(string prompt, ...);

#include <cs50.h>

double get_double(const char *format, ...);


This function prompts the user for a double. If the user inputs anything other than a double (or a value that cannot fit in a double), the function prompts the user again.

This function expects at least one argument, prompt. If prompt contains any format codes, a la printf, this function accepts additional arguments as well, one per format code.

Prompts user for a line of text from standard input and returns the equivalent double as precisely as possible; if text does not represent a double or would cause underflow or overflow, user is reprompted.

The prompt is formatted like printf(3).


This function returns the user’s input as precisely as possible as a double.

Returns the double equivalent to the line read from stdin in [DBL_MIN, DBL_MAX), as precisely as possible. If line can’t be read, returns DBL_MAX.


#include <cs50.h>
#include <stdio.h>
int main(void) { double d = get_double("Input: "); printf("Output: %f\n", d); }
 * Returns the quotient of two doubles, or DBL_MAX on error.
double divide_doubles(void)
    // read double from stdin
    double d = get_double("Enter a double: ");

    // make sure we read one successfully
    if (d == DBL_MAX)
        return DBL_MAX;

    double e = get_double("What do you want to divide %lf by? ", d);

    // make sure we don't divide by zero
    if (e == DBL_MAX || e == 0.0)
        return DBL_MAX;

    return i / j;


get_char(3), get_float(3), get_int(3), get_long(3),
get_string(3), printf(3)