Functions

A FUNCTION returns a value

• A function works something out and hands back a value with RETURN.
• RETURNS (in the header) states the type of value it gives back.

FUNCTION Square(Number : INTEGER) RETURNS INTEGER
    RETURN Number * Number
ENDFUNCTION

OUTPUT Square(6)        // → 36

Use the returned value

• Call a function inside an expression, or store its result in a variable.

FUNCTION Square(Number : INTEGER) RETURNS INTEGER
    RETURN Number * Number
ENDFUNCTION

DECLARE Answer : INTEGER
Answer ← Square(4)
OUTPUT Answer + 1       // → 17

A function can return a Boolean

• The result can be a BOOLEAN — handy for a yes/no test.

FUNCTION IsPositive(Number : INTEGER) RETURNS BOOLEAN
    RETURN Number > 0
ENDFUNCTION

OUTPUT IsPositive(5)    // → TRUE

Watch out

• A procedure does something; a function returns a value you then use.
• Every path through a function must reach a RETURN.

Common mistakes

• FUNCTION Name(...) RETURNS TYPE ... RETURN Value ... ENDFUNCTION.
• A function must RETURN a value.

Now you try

• Define a function with RETURNS and RETURN.
• Press Check answer to test it.