michael@0: 
michael@0: assertEq("foo".charAt(-123), "");
michael@0: assertEq("foo".charAt(-1), "");
michael@0: assertEq("foo".charAt(0), "f");
michael@0: assertEq("foo".charAt(1), "o");
michael@0: assertEq("foo".charAt(2), "o");
michael@0: assertEq("foo".charAt(3.4), "");
michael@0: assertEq("foo".charAt(), "f");
michael@0: assertEq("".charAt(), "");
michael@0: assertEq("".charAt(0), "");
michael@0: assertEq("abc\u9123".charAt(3), "\u9123"); // char without unit string
michael@0: 
michael@0: /* Inferred as string.charAt(int). */
michael@0: function charAt1(x) {
michael@0:     return "abc".charAt(x);
michael@0: }
michael@0: assertEq(charAt1(-1), "");
michael@0: assertEq(charAt1(0), "a");
michael@0: assertEq(charAt1(1), "b");
michael@0: assertEq(charAt1(2), "c");
michael@0: assertEq(charAt1(3), "");
michael@0: assertEq(charAt1(1234), "");
michael@0: 
michael@0: /* Inferred as string.charAt(double). */
michael@0: function charAt2(x) {
michael@0:     return "abc".charAt(x);
michael@0: }
michael@0: assertEq(charAt2(-1.3), "");
michael@0: assertEq(charAt2(-0), "a");
michael@0: assertEq(charAt2(2), "c");
michael@0: assertEq(charAt2(2.3), "c");
michael@0: assertEq(charAt2(3.14), "");
michael@0: assertEq(charAt2(NaN), "a");
michael@0: 
michael@0: /* Test ropes. */
michael@0: function charAt3(s, i) {
michael@0:     var s2 = "abcdef" + s + "12345";
michael@0:     return s2.charAt(i);
michael@0: }
michael@0: assertEq(charAt3("abcdef", 14), "3");
michael@0: assertEq(charAt3("a" + "b", 1), "b");
michael@0: assertEq(charAt3("abcdefg" + "hijklmnop", 10), "e");
michael@0: 
michael@0: /* Other 'this'. */
michael@0: var arr = [1, 2];
michael@0: arr.charAt = String.prototype.charAt;
michael@0: assertEq(arr.charAt(1), ",");
michael@0: 
michael@0: