Data commit

Task/Conditional-structures/Zig/conditional-structures.zig

@@ -0,0 +1,63 @@
+const std = @import("std");
+const builtin = @import("builtin");
+
+fn printOpenSource(comptime is_open_source: bool) !void {
+    if (is_open_source) {
+        try std.io.getStdOut().writer().writeAll("Open source.\n");
+    } else {
+        try std.io.getStdOut().writer().writeAll("No open source.\n");
+    }
+}
+fn printYesOpenSource() !void {
+    try std.io.getStdOut().writer().writeAll("Open source.\n");
+}
+fn printNoOpenSource() !void {
+    try std.io.getStdOut().writer().writeAll("No open source.\n");
+}
+const fnProto = switch (builtin.zig_backend) {
+    .stage1 => fn () anyerror!void,
+    else => *const fn () anyerror!void,
+};
+const Vtable = struct {
+    fnptrs: [2]fnProto,
+};
+
+// dynamic dispatch: logic(this function) + vtable + data
+fn printBySelectedType(data: bool, vtable: Vtable) !void {
+    if (data) {
+        try @call(.{}, vtable.fnptrs[0], .{});
+    } else {
+        try @call(.{}, vtable.fnptrs[1], .{});
+    }
+}
+
+pub fn main() !void {
+    // if-else
+    if (true) {
+        std.debug.assert(true);
+    } else {
+        std.debug.assert(false);
+    }
+    // comptime switch
+    const open_source = comptime switch (builtin.os.tag) {
+        .freestanding => true,
+        .linux => true,
+        .macos => false,
+        .windows => false,
+        else => unreachable,
+    };
+    // conditional compilation
+    std.debug.assert(builtin.zig_backend != .stage2_llvm);
+    // static dispatch (more complex examples work typically via comptime enums)
+    try printOpenSource(open_source);
+    // dynamic dispatch (runtime attach function pointer)
+    var vtable = Vtable{
+        .fnptrs = undefined,
+    };
+    // runtime-attach function pointers (dynamic dispatch)
+    vtable.fnptrs[0] = printYesOpenSource;
+    vtable.fnptrs[1] = printNoOpenSource;
+    try printBySelectedType(open_source, vtable);
+
+    // TODO Arithmetic if once https://github.com/ziglang/zig/issues/8220 is finished
+}