if.md

The if Function

Using an if-then-else structure in Cell works differently from in other languages, because in Cell, if is a function, not a special construct.

The if function takes in 3 arguments: a test, and two functions. The first function will be called if the test is true, and the second will be called if the test is false.

The test must be a number, and if it's zero, Cell considers it false. Otherwise, Cell considers it true.

Here is an example:

flower = "rose";

if ( equals( flower, "rose" ),
    {
        print( "The flower is a rose." );
    },
    {
        print( "No roses today." );
    }
);

if ( equals( flower, "violet" ),
    {
        print( "Violets!!!!" );
    },
    {
        print( "No violets." );
    }
);

When we run this program, it prints this:

The flower is a rose.
No violets.

The parts that start and end with { and } are actually functions that take no arguments. The if function calls one or other of them, depending on the result of the test passed in as its first argument.

Above, the tests that were passed in were equals( flower, "rose" ) and equals( flower, "violet" ). The equals function returns a true value if its two arguments are the same, and a false value otherwise.

You can find out more about defining and using functions on the Syntax page.