add 071 comptime 6 inline for

TEMP_TODO

@@ -0,0 +1,4 @@
+071 - inline for - loop through struct fields
+072 - inline while (see lib/std/fmt.zig)
+073 - comptime block
+074 - quiz 8 - revisit 058_quiz7 and make those connections programatically?

build.zig

@@ -353,6 +353,10 @@ const exercises = [_]Exercise{
         .output = "\"Quack.\" ducky1: true, \"Squeek!\" ducky2: true, ducky3: false",
         .hint = "Have you kept the wizard hat on?",
     },
+    .{
+        .main_file = "071_comptime6.zig",
+        .output = "Narcissus has room in his heart for: me myself.",
+    },
 };
 
 /// Check the zig version to make sure it can compile the examples properly.

exercises/065_builtins2.zig

@@ -90,7 +90,7 @@ pub fn main() void {
     // A StructFields array
     const fields = @typeInfo(Narcissus).Struct.fields;
 
-    // 'fields' is an array of StructFields. Here's the declaration:
+    // 'fields' is a slice of StructFields. Here's the declaration:
     //
     //     pub const StructField = struct {
     //         name: []const u8,

exercises/071_comptime6.zig

@@ -0,0 +1,56 @@
+//
+// There have been several instances where it would have been
+// nice to use loops in our programs, but we couldn't because the
+// things we were trying to do could only be done at compile
+// time. We ended up having to do those things MANUALLY, like
+// NORMAL people. Bah! We are PROGRAMMERS! The computer should be
+// doing this work.
+//
+// An 'inline for' is performed at compile time, allowing you to
+// programatically loop through a series of items in situations
+// like those mentioned above where a regular runtime 'for' loop
+// wouldn't be allowed:
+//
+//     inline for (.{ u8, u16, u32, u64 }) |T| {
+//         print("{} ", .{@typeInfo(T).Int.bits});
+//     }
+//
+// In the above example, we're looping over a list of types,
+// which are available only at compile time.
+//
+const print = @import("std").debug.print;
+
+// Remember Narcissus from exercise 065 where we used builtins
+// for reflection? He's back and loving it.
+const Narcissus = struct {
+    me: *Narcissus = undefined,
+    myself: *Narcissus = undefined,
+    echo: void = undefined,
+};
+
+pub fn main() void {
+    var narcissus: Narcissus = Narcissus {};
+
+    print("Narcissus has room in his heart for:", .{});
+
+    // Last time we examined the Narcissus struct, we had to
+    // manually access each of the three fields. Our 'if'
+    // statement was repeated three times almost verbatim. Yuck!
+    //
+    // Please use an 'inline for' to implement the block below
+    // for each field in the slice 'fields'!
+
+    const fields = @typeInfo(Narcissus).Struct.fields;
+
+    ??? {
+        if (field.field_type != void) {
+            print(" {s}", .{field.name});
+        }
+    }
+
+    // Once you've got that, go back and take a look at exercise
+    // 065 and compare what you've written to the abomination we
+    // had there!
+
+    print(".\n", .{});
+}

patches/patches/071_comptime6.patch

@@ -0,0 +1,4 @@
+45c45
+<     ??? {
+---
+>     inline for (fields) |field| {