CODEWITHSUNDEEP
cgtkdouble
Randy Banks
Randy Banks

Reputation: 371

Representing a double as an array of characters in C

I am working with GTK, and in my program I am taking a user input, converting it from a string to a double using atof() in order to make computations, and then outputting the result into an entry. My problem is when using 

void gtk_entry_set_text( GtkEntry *entry, const gchar *text );

I obviously need to pass the second argument as a gchar (or just a regular pointer to an array of characters), but I am not sure how to convert my double back into a human readable representation of the double. For example, user enters 65.0. I convert the string "65.0" to a double 65.0, perform my function (say multiply by two), and now I need to convert the double 130.0 into "130.0", and then store it into a character array to be passed into gtk_entry_set_text. How can I achieve this?

To help clarify as much as possible, here is the code in question.

/* function for calculating optimal amount of cash to bet */
static void calculateRatioOfCash()
{
    const gchar *userInput;
    char outputString[BUFSIZ];

    /* retrieve probability of winning from input field */
    userInput = gtk_entry_get_text(GTK_ENTRY(entry));

    /* convert our probability in str to a double and compute betPercentage */
    double betPercentage = 2*(atof(userInput)) - 100;

    outputString = /* what code goes here ?? */

    gtk_entry_set_text(GTK_ENTRY(outputField), outputString);

}

Upvotes: 0

Views: 231

Answers (2)

Jussi Kukkonen
Jussi Kukkonen

Reputation: 14607

Since you are using GLib already, I'd suggest using GLib string utility functions. In this case:

char *output = g_strdup_printf ("%f", betPercentage);

This is easier than using sprintf() because it allocates memory for you -- of course it means you should g_free (output) when you're done with it.

Upvotes: 1

Sadique
Sadique

Reputation: 22821

Use sprintf. Something like this:

sprintf(buf, "%lf", a)

Sample.

sprintf(outputString, "%lf", betPercentage)

Upvotes: 2

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