Added Ex. 100 fourth for (as foretold in #261)

1 files changed, 62 insertions, 0 deletions

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+//
+// We've seen that the 'for' loop can let us perform some action
+// for every item in an array or slice.
+//
+// More recently, we discovered that it supports ranges to
+// iterate over number sequences.
+//
+// This is part of a more general capability of the `for` loop:
+// looping over one or more "objects" where an object is an
+// array, slice, or range.
+//
+// In fact, we *did* use multiple objects way back in Exercise
+// 016 where we iterated over an array and also a numeric index.
+// It didn't always work exactly this way, so the exercise had to
+// be retroactively modified a little bit.
+//
+//     for (bits, 0..) |bit, i| { ... }
+//
+// The general form of a 'for' loop with two lists is:
+//
+//     for (list_a, list_b) |a, b| {
+//         // Here we have the first item from list_a and list_b,
+//         // then the second item from each, then the third and
+//         // so forth...
+//     }
+//
+// What's really beautiful about this is that we don't have to
+// keep track of an index or advancing a memory pointer for
+// *either* of these lists. That error-prone stuff is all taken
+// care of for us by the compiler.
+//
+// Below, we have a program that is supposed to compare two
+// arrays. Please make it work!
+//
+const std = @import("std");
+const print = std.debug.print;
+
+pub fn main() void {
+    const hex_nums = [_]u8{ 0xb, 0x2a, 0x77 };
+    const dec_nums = [_]u8{ 11, 42, 119 };
+
+    for (hex_nums, ???) |hn, ???| {
+        if (hn != dn) {
+            std.debug.print("Uh oh! Found a mismatch: {d} vs {d}\n", .{ hn, dn });
+            return;
+        }
+    }
+
+    std.debug.print("Arrays match!\n", .{});
+}
+//
+// You are perhaps wondering what happens if one of the two lists
+// is longer than the other? Try it!
+//
+// By the way, congratulations for making it to Exercise 100!
+//
+//    +-------------+
+//    | Celebration |
+//    | Area  * * * |
+//    +-------------+
+//
+// Please keep your celebrating within the area provided.