if

Arguments

Returns

The evaluation of the statement that corresponds to the satisfied condition.

Description

The if statement evaluates its condition and tests the result. If the result is non-nil, then the statement is evaluated and the result returned.

The else option allows for another statement. If the condition is nil, the else statement (if included) is evaluated and the result returned. This statement could be another if statement with another condition and else statement, etc., permitting multiple else/if constructs. The entire else option can be omitted if desired.

If the condition is nil and no else statement exists, nil is returned. The else part of a nested if statement will always be associated with the closest if statement when ambiguity exists. Ambiguity can be avoided by explicitly defining code blocks (using curly brackets). In interactive mode Gamma has to read two tokens (if and else) before it will process the statement. If you are not using an else part, you have to enter a second semicolon (;) to indicate that the if statement is ready for processing.

Example

    Gamma> x = 5;
    5
    Gamma> y = 6;
    6
    Gamma> if (x > y) princ("greater\n"); else princ("not greater\n");
    not greater
    t
    Gamma> 

The following code:

    name = "John";
    age = 35;
    
    if ((name == "Hank") || (name == "Sue"))
    {
        princ("Hi ", name,"\n");
    }
    else if ((name == "John") && (age < 20))
    {
        princ("Hi ", name," Junior\n");
    }
    else if ((name == "John") && (age >= 20))
    {
        princ("Hi ", name," Senior\n");
    }
    else
    {
        princ("I don't know you\n");
    }

Will produce the following results:

    Hi John Senior
    		

See the introduction or the Monitor Window section of the Photon Functions chapter (Tutorial One), or the Starting Programs section of the Common Functions for Any Program chapter (Tutorial Two) in the Cogent Tools Demo and Tutorials book for examples of this function used in context.

See Also

Statements, for, while