This issue was originally filed by ross.dart...@gmail.com

Dart SDK version 0.5.13.1_r23552

rationale:

We currently have the following typedef in 'dart:core':

typedef int Comparator<T>(T a, T b);

I'm proposing to add a symmetric companion:

typedef bool Predicate<E>(E element);

Many of the methods on Iterable<E> take a test function of the form:

bool test(E element)

I am not proposing to change these signatures to take a Predicate. What I am proposing, is to offer the typedef in dart:core so that I can store typed references to Functions that are used on Iterables. Keep the loose coupling, but don't require me to typedef my own Predicate type to stock these Function references.

This would be symmetric to how List.sort takes an int compare(E a, E b) yet the dartdoc refers to the usage as a Comparator.

thanks,