051 expand stdlib wrap

// Test: [expand] for stdlib wrapping with Zig's @TypeOf generics
//
// This demonstrates the pattern for wrapping Zig stdlib functions:
// 1. Define a template with {{ }} Liquid placeholders
// 2. Use Zig's @TypeOf for "free generics" - no Koru type system complexity
// 3. Declare [norun|expand] event - implementation comes from template
//
// Result: Zero-cost, type-safe stdlib wrappers with clean Koru syntax.

~import "$std/template"

const std = @import("std");

// Template uses @TypeOf to infer element type from the array itself
// This gives us generics "for free" - Zig figures out the types!
~std.template:define(name: "sort") {
    std.mem.sort(@TypeOf({{ arr }}[0]), {{ arr }}, {}, std.sort.asc(@TypeOf({{ arr }}[0])));
}

// [norun] = no proc needed, event just stores shape
// [expand] = transform replaces invocation with template expansion
~[norun|expand]pub event sort { arr: Expression }

// Test data
var numbers = [_]i32{ 5, 2, 8, 1, 9, 3 };

// Use it! The ~ makes it a Koru flow, [expand] inlines the template
~sort(arr: numbers[0..])

// Verify it worked
~event verify {}

~proc verify {
    // Check sorted order
    var prev: i32 = numbers[0];
    for (numbers[1..]) |n| {
        if (n < prev) {
            std.debug.print("FAIL: {d} < {d}\n", .{ n, prev });
            return;
        }
        prev = n;
    }
    std.debug.print("PASS: array sorted correctly\n", .{});
}

~verify()