Vocabulary
game.input

Inputs and outputs

old?	a boolean
new?	a boolean
delta	pressed, released, or f

Word description
Outputs a symbol representing the change in a key or button's state given a "before" and "after" sample of its state. Outputs pressed if old? is false and new? is true, released if old? is true and new? is false, or f if the two inputs have the same boolean value.

See also
buttons-delta, buttons-delta-as

Definition

USING: combinators kernel ;

IN: game.input

: button-delta ( old? new? -- delta )
{
{ [ 2dup xor not ] [ 2drop f ] }
{ [ dup not ] [ 2drop released ] }
{ [ over not ] [ 2drop pressed ] }
} cond ; inline