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85 lines
2.3 KiB
Zig
85 lines
2.3 KiB
Zig
//
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// Struct types are always "anonymous" until we give them a name:
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//
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// struct {};
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//
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// So far, we've been giving struct types a name like so:
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//
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// const Foo = struct {};
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//
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// * The value of @typeName(Foo) is "<filename>.Foo".
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//
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// A struct is also given a name when you return it from a
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// function:
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//
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// fn Bar() type {
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// return struct {};
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// }
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//
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// const MyBar = Bar(); // store the struct type
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// const bar = Bar() {}; // create instance of the struct
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//
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// * The value of @typeName(Bar()) is "Bar()".
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// * The value of @typeName(MyBar) is "Bar()".
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// * The value of @typeName(@TypeOf(bar)) is "Bar()".
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//
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// You can also have completely anonymous structs. The value
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// of @typeName(struct {}) is "struct:<position in source>".
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//
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const print = @import("std").debug.print;
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// This function creates a generic data structure by returning an
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// anonymous struct type (which will no longer be anonymous AFTER
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// it's returned from the function).
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fn Circle(comptime T: type) type {
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return struct {
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center_x: T,
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center_y: T,
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radius: T,
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};
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}
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pub fn main() void {
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//
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// See if you can complete these two variable initialization
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// expressions to create instances of circle struct types
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// which can hold these values:
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//
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// * circle1 should hold i32 integers
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// * circle2 should hold f32 floats
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//
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const circle1 = ??? {
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.center_x = 25,
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.center_y = 70,
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.radius = 15,
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};
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const circle2 = ??? {
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.center_x = 25.234,
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.center_y = 70.999,
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.radius = 15.714,
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};
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print("[{s}: {},{},{}] ", .{
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stripFname(@typeName(@TypeOf(circle1))),
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circle1.center_x,
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circle1.center_y,
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circle1.radius,
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});
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print("[{s}: {d:.1},{d:.1},{d:.1}]\n", .{
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stripFname(@typeName(@TypeOf(circle2))),
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circle2.center_x,
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circle2.center_y,
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circle2.radius,
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});
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}
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// Perhaps you remember the "narcissistic fix" for the type name
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// in Ex. 065? We're going to do the same thing here: use a hard-
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// coded slice to return the type name. That's just so our output
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// looks prettier. Indulge your vanity. Programmers are beautiful.
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fn stripFname(mytype: []const u8) []const u8 {
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return mytype[22..];
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}
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// The above would be an instant red flag in a "real" program.
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