maghoff/infix

An implementation of infix notation for custom number types in JavaScript

infix's Issues

Add memoizing evaluator

Using evaluate is good for readability: the evaluated expression appears in the code where it is executed. Using compile is good for execution speed: parsing of both the expression and the contained constants gets to happen ahead of time. The presumed "hot code path" is thus optimized.

Can we get both?

A memoizing evaluator could probably achieve a speedup when compared to evaluate as well as an improvement in readability compared to compile. It would look just like evaluate but internally use some memoization, maybe like this:

var memoizedExpressions = {};

function memoizingEvaluator(expression, numberProvider) {
    var f = memoizedExpressions[expression];
    if (!f) f = memoizedExpressions[expression] = compile(expression, numberProvider);
    return f();
}

Add `evaluate` which doesn't accept placeholders

The basic arithmetic syntax can be useful for accepting user input. For this use case, it is confusing that placeholders are accepted. infix could offer a version of evaluate which does not accept placeholders to solve this use case.

It makes less sense to have this version of the compiler. Compiled expressions mostly make sense with placeholders. So, it is sufficient only to implement the requisite evaluate function.