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 load(libdir + 'iteration.js');

 let makeCall    = farg => Function("f", "arg", "return f(" + farg + ");");

 let makeFunCall = farg => Function("f", "arg", "return f.call(null, " + farg + ");");

 let makeNew     = farg => Function("f", "arg", "return new f(" + farg + ").length;");

 function checkLength(f, makeFn) {

   assertEq(makeFn("...[1, 2, 3]")(f), 3);

   assertEq(makeFn("1, ...[2], 3")(f), 3);

   assertEq(makeFn("1, ...[2], ...[3]")(f), 3);

   assertEq(makeFn("1, ...[2, 3]")(f), 3);

   assertEq(makeFn("1, ...[], 2, 3")(f), 3);

   assertEq(makeFn("...[1]")(f), 1);

   assertEq(makeFn("...[1, 2]")(f), 2);

   assertEq(makeFn("...[1, 2, 3, 4]")(f), 4);

   assertEq(makeFn("1, ...[2, 3, 4], 5")(f), 5);

   assertEq(makeFn("...[undefined]")(f), 1);

   // other iterable objects

   assertEq(makeFn("...arg")(f, new Int32Array([1, 2, 3])), 3);

   assertEq(makeFn("...arg")(f, "abc"), 3);

   assertEq(makeFn("...arg")(f, [1, 2, 3][std_iterator]()), 3);

   assertEq(makeFn("...arg")(f, Set([1, 2, 3])), 3);

   assertEq(makeFn("...arg")(f, Map([["a", "A"], ["b", "B"], ["c", "C"]])), 3);

   let itr = {};

   itr[std_iterator] = function() {

       return {

           i: 1,

           next: function() {

               if (this.i < 4)

                   return { value: this.i++, done: false };

               else

                   return { value: undefined, done: true };

           }

       };

   }

   assertEq(makeFn("...arg")(f, itr), 3);

   function* gen() {

       for (let i = 1; i < 4; i ++)

           yield i;

   }

   assertEq(makeFn("...arg")(f, gen()), 3);

 }

 checkLength(function(x) arguments.length, makeCall);

 checkLength(function(x) arguments.length, makeFunCall);

 checkLength((x) => arguments.length, makeCall);

 checkLength((x) => arguments.length, makeFunCall);

 function lengthClass(x) {

   this.length = arguments.length;

 }

 checkLength(lengthClass, makeNew);