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Useful Utilities

In this article, we discuss useful utilities that you can use to convert, check and manipulate common data types in SplashKit programs.
Written by: Richard Denton and others
Last updated: October 2024

SplashKit’s Utilities library provides a range of useful functions that can assist you with converting, checking, and manipulating common data types in your SplashKit program.

These functions are useful in many areas of programming.

Before getting started with these utilities functions, it is important to be able to get inputs from the user using the command line (terminal).

Reading Text from the Command Line

Section titled “Reading Text from the Command Line”

Reading text input from the user is straightforward for terminal-based applications.

In this context, Read Line allows you to read a line of text entered at the Terminal. This is a blocking function call, meaning it waits for the user to input the line before it returns. For command line applications, this is fine; you want it to wait for the input.

The following code demonstrates the use of Read Line in order to read in and display the user’s name.

#include "splashkit.h"


int main()
{
    string name;  // declare a variable to store the name
    string quest; // and another to store a quest


    write("What is your name: "); // prompt the user for input
    name = read_line();           // read user input


    // read in another value
    write("And what is your quest? ");
    quest = read_line();


    write_line(name + "'s quest is: " + quest); // output quest to the terminal


    return 0;
}

Converting a string to a number

Section titled “Converting a string to a number”

SplashKit provides two useful functions for handling the conversion of a string to either an int or a double.

#include "splashkit.h"


int main()
{
    // Convert the string "2017" to an integer 2017
    string some_string = "2017";
    int some_number = convert_to_integer(some_string);


    write("The value of some_number is: ");
    write_line(some_number);


    // Convert the string "3.14159265358979" to a double ~3.141593
    string pi_string = "3.14159265358979";
    double pi = convert_to_double(pi_string);


    write("The value of pi is: ");
    write_line(pi);


    return 0;
}

Usage scenario: Converting user input to an integer

Section titled “Usage scenario: Converting user input to an integer”

Consider you want to write a program that accepts two numbers as input from a user, multiplies them, and outputs the result. One way to accomplish this is to use SplashKit’s Convert To Integer function.

#include "splashkit.h"


int main()
{
    // User input will initially be stored in these two strings.
    string snum_1, snum_2;


    // And then it will be converted and stored in these integers.
    int inum_1, inum_2, result;


    // Read user input
    write("Enter first number: ");
    snum_1 = read_line();
    write("Enter second number: ");
    snum_2 = read_line();


    // Convert user input to integers
    inum_1 = convert_to_integer(snum_1);
    inum_2 = convert_to_integer(snum_2);


    // Compute the result
    result = inum_1 * inum_2;


    // Output the results
    write(snum_1 + " multiplied by " + snum_2 + " equals ");
    write_line(result);


    return 0;
}

The same can be achieved for decimal numbers, simply by swapping convert_to_integer with convert_to_double, and using the appropriate data types.

//...


//Don't use integers, instead use doubles
double inum_1, inum_2, result;


//...


inum_1 = convert_to_double(snum_1);
inum_2 = convert_to_double(snum_2);


//...

Checking if a string is a number

Section titled “Checking if a string is a number”

Another helpful set of functions provided by SplashKit’s utilities library is Is Integer and Is Number.

Consider the following.

#include "splashkit.h"


int main()
{
    string message_1 = "9781273";
    string message_2 = "23129739.13";
    string message_3 = "Hello world.";


    if (is_integer(message_1))
        write_line("Message 1 contains an integer!");


    if (is_number(message_1))
        write_line("Message 1 contains a number!");


    if (not is_integer(message_2))
        write_line("Message 2 is not an integer!");


    if (is_number(message_2))
        write_line("Message 2 contains a number!");


    if (not is_integer(message_3))
        write_line("Message 3 is not an integer!");


    if (not is_number(message_3))
        write_line("Message 3 is not a number!");


    return 0;
}

The terminal output should be:

Message 1 contains an integer!
Message 1 contains a number!
Message 2 is not an integer!
Message 2 contains a number!
Message 3 is not an integer!
Message 3 is not a number!

Usage scenario: accept user input as a number

Section titled “Usage scenario: accept user input as a number”

SplashKit’s Is Integer and Is Number functions can be used to validate user input, ensuring the user always enters a valid data type.

#include "splashkit.h"
#include <string>


using namespace std;


/**
 * Reads input from a user, only allowing whole numbers.
 * @prompt string     - The string to display to the user.
 * @return int
 */
int read_integer(string prompt)
{


    // Prompt the user with the message
    write(prompt);


    // Read the user input as a string.
    string line = read_line();


    // Check if user input is a valid whole number, loop until it is.
    while (!is_integer(line))
    {
        write_line("Please enter a whole number.");


        write(prompt);
        line = read_line();
    }


    // Convert the user input to an integer before returning it.
    return convert_to_integer(line);
}


int main()
{
    int height;


    height = read_integer("Enter your height in centimetres: ");
    write("You are ");
    write(height);
    write_line("CM tall!");


    return 0;
}

Manipulating strings

Section titled “Manipulating strings”

In addition to the functionality provided by each language’s standard library (The string library in C++, and the System library in C#), SplashKit’s utilities library provides some extra string manipulation functions that can assist you with manipulating string data.

#include "splashkit.h"


int main()
{
    string name = "Richard";
    string location = "        Burwood";


    // Convert "Richard" to "RICHARD"
    name = to_uppercase(name);
    write_line(name);


    // Convert "RICHARD" to "richard"
    name = to_lowercase(name);
    write_line(name);


    // Remove all of the empty spaces at the start of "       Burwood".
    write_line("Before: " + location);
    location = trim(location);
    write_line("After: " + location);


    return 0;
}