destructuring

Destructuring allows the specification of several values at once, when their value is extracted from a Tuple or Entry.

Usage

// destructure an Entry
value key->item = entry;

[Float, Float, Float] point = [1.0, 1.0, 1.0];
// declare three values extracting the valee of each from the tuple
value [x, y, z] = point;

[Float, Float, Float]? maybePoint = point;
// in conjunction with the exists condition
if (exists [x, y, z] =  maybePoint) {
    // ...
}

[Float+] floats = [0.0, 1.0, 2.0, 3.0];
// destructure with spread
value [first, *rest] = floats;

[Float, Float, [String, Icon]] labelledPoint = ...;
// nested destructure
value [x, y, [name, icon]] = labelledPoint;

Description

Destructuring specification is supported:

• In value declarations (value [x, y] = point),
• In for iteration variables (for ([x, y] in points) { ... }),
• In condition lists (if (exists [x, y]=maybePoint) { ... }, assert(exists [x, y]=maybePoint);, assert(nonempty [first, *rest]=seq); etc),
• In cases of a switch (case ([Float x, Float y]) { ... }),
• In let expressions (let ([x, y] = point) sqrt(x^2+y^2)),
• In comprehensions ({ for[x, y] in points) sqrt(x^2+y^2) }),

It is not supported for types other than Tuple or Entry.

See also