Function pareen::cond

pub fn cond<T, V, F, G, H, Cond, A, B>(
    cond: Cond, 
    a: A, 
    b: B
) -> Anim<impl Fun<T = T, V = V>> where
    T: Copy,
    F: Fun<T = T, V = bool>,
    G: Fun<T = T, V = V>,
    H: Fun<T = T, V = V>,
    Cond: Into<Anim<F>>,
    A: Into<Anim<G>>,
    B: Into<Anim<H>>, 

Return the value of one of two animations depending on a condition.

This allows returning animations of different types conditionally.

Note that the condition cond may either be a value true and false, or it may itself be a dynamic animation of type bool.

For dynamic conditions, in many cases it suffices to use either Anim::switch or Anim::seq instead of this function.

Examples

Constant conditions

The following example does not compile, because the branches have different types:

let cond = true;
let anim = if cond { pareen::constant(1) } else { pareen::id() };

However, this does compile:

let cond = true;
let anim = pareen::cond(cond, 1, pareen::id());

assert_eq!(anim.eval(2), 1);

Dynamic conditions

let cond = pareen::fun(|t| t * t <= 4);
let anim_1 = 1;
let anim_2 = pareen::id();
let anim = pareen::cond(cond, anim_1, anim_2);

assert_eq!(anim.eval(1), 1); // 1 * 1 <= 4
assert_eq!(anim.eval(2), 1); // 2 * 2 <= 4
assert_eq!(anim.eval(3), 3); // 3 * 3 > 4