let

Pipes a composed sequence to be mapped through a function so it can be used multiple times

function let(func : Function) : IObservable.<T>

Where func is function (input : IObservable.<T>) : IObservable.<T>

Remarks

Let allows a sequence to be reused without having to assign it to a local variable first.

The returned sequence completes if the source sequence completes

The returned sequence errors if the source sequence errors or if func throws an error

Marble Diagrams

xs ─┐
   f()
    └───o─────o──/
        │     │  │
zs ─────o─────o──/

Return Value

IObservable.<T>

Examples

Observable.range(1, 5)
    .map(function (x: int) : int { return x * 2; })
    .let(function(source : IObservable) : IObservable
    {
        // 'source' is 'range.select()', but we can use it as a unit here
        return source.zip(source.skip(1), function(x:int, y:int) : int
        {
            return x * y;
        });
    });
    .subscribe(
        function(x:int) : void { trace(x); },
        function() : void { trace("Completed"); }
    );

    // Trace output is:
    // 8
    // 24
    // 48
    // 80
    // Completed