Cannot assign to constant value through lambda.

brad_phelan · February 2018

Attempt to do a standard functional programming trick

but I get that I cannot assign to "const" value. Is there any way to write generators in featurescript? I also tried.

Image: https://us.v-cdn.net/5022071/uploads/editor/7t/g72rctk8wtqz.png

to the same error. Have also tried arrays instead of maps. Nothing work to inject some state into the lambda.

john_f_carr · February 2018

You need to use a box, which is mutable and can escape its defining scope:

function incrementer()
{
    const counter = new box(0);
    return function() { counter[] += 1; return counter[]; };
}

Jake_Rosenfeld · February 2018

This does what you want:

function generator(value is number)
{
    var valueBox = new box(value);
    return function() {
        valueBox[] += 1;
        return valueBox[];
    };
}

https://cad.onshape.com/documents/e39bbc03ade7ea27cba2656f/w/52a2f86fe05dfd95d6c5963b/e/23f61f89801e865ffacfaf55
https://cad.onshape.com/FsDoc/variables.html (see 'Box')

Cannot assign to constant value through lambda.

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