michael@0: load(libdir + 'iteration.js');
michael@0: 
michael@0: let makeCall    = farg => Function("f", "arg", "return f(" + farg + ");");
michael@0: let makeFunCall = farg => Function("f", "arg", "return f.call(null, " + farg + ");");
michael@0: let makeNew     = farg => Function("f", "arg", "return new f(" + farg + ").length;");
michael@0: 
michael@0: function checkLength(f, makeFn) {
michael@0:   assertEq(makeFn("...[1, 2, 3]")(f), 3);
michael@0:   assertEq(makeFn("1, ...[2], 3")(f), 3);
michael@0:   assertEq(makeFn("1, ...[2], ...[3]")(f), 3);
michael@0:   assertEq(makeFn("1, ...[2, 3]")(f), 3);
michael@0:   assertEq(makeFn("1, ...[], 2, 3")(f), 3);
michael@0: 
michael@0:   assertEq(makeFn("...[1]")(f), 1);
michael@0:   assertEq(makeFn("...[1, 2]")(f), 2);
michael@0:   assertEq(makeFn("...[1, 2, 3, 4]")(f), 4);
michael@0:   assertEq(makeFn("1, ...[2, 3, 4], 5")(f), 5);
michael@0: 
michael@0:   assertEq(makeFn("...[undefined]")(f), 1);
michael@0: 
michael@0:   // other iterable objects
michael@0:   assertEq(makeFn("...arg")(f, new Int32Array([1, 2, 3])), 3);
michael@0:   assertEq(makeFn("...arg")(f, "abc"), 3);
michael@0:   assertEq(makeFn("...arg")(f, [1, 2, 3][std_iterator]()), 3);
michael@0:   assertEq(makeFn("...arg")(f, Set([1, 2, 3])), 3);
michael@0:   assertEq(makeFn("...arg")(f, Map([["a", "A"], ["b", "B"], ["c", "C"]])), 3);
michael@0:   let itr = {};
michael@0:   itr[std_iterator] = function() {
michael@0:       return {
michael@0:           i: 1,
michael@0:           next: function() {
michael@0:               if (this.i < 4)
michael@0:                   return { value: this.i++, done: false };
michael@0:               else
michael@0:                   return { value: undefined, done: true };
michael@0:           }
michael@0:       };
michael@0:   }
michael@0:   assertEq(makeFn("...arg")(f, itr), 3);
michael@0:   function* gen() {
michael@0:       for (let i = 1; i < 4; i ++)
michael@0:           yield i;
michael@0:   }
michael@0:   assertEq(makeFn("...arg")(f, gen()), 3);
michael@0: }
michael@0: 
michael@0: checkLength(function(x) arguments.length, makeCall);
michael@0: checkLength(function(x) arguments.length, makeFunCall);
michael@0: checkLength((x) => arguments.length, makeCall);
michael@0: checkLength((x) => arguments.length, makeFunCall);
michael@0: function lengthClass(x) {
michael@0:   this.length = arguments.length;
michael@0: }
michael@0: checkLength(lengthClass, makeNew);