54 lines
1.8 KiB
Zig
54 lines
1.8 KiB
Zig
//
|
|
// One of the more common uses of 'comptime' function parameters is
|
|
// passing a type to a function:
|
|
//
|
|
// fn foo(comptime MyType: type) { ... }
|
|
//
|
|
// In fact, types are ONLY available at compile time, so the
|
|
// 'comptime' keyword is required here.
|
|
//
|
|
// Please take a moment put on the wizard hat which has been
|
|
// provided for you. We're about to use this ability to implement
|
|
// a generic function.
|
|
//
|
|
const print = @import("std").debug.print;
|
|
|
|
pub fn main() void {
|
|
// Here we declare arrays of three different types and sizes
|
|
// at compile time from a function call. Neat!
|
|
const s1 = makeSequence(u8, 3); // creates a [3]u8
|
|
const s2 = makeSequence(u32, 5); // creates a [5]u32
|
|
const s3 = makeSequence(i64, 7); // creates a [7]i64
|
|
|
|
print("s1={any}, s2={any}, s3={any}\n", .{s1, s2, s3});
|
|
}
|
|
|
|
// This function is pretty wild because it executes at runtime
|
|
// and is part of the final compiled program. The function is
|
|
// compiled with unchanging data sizes and types.
|
|
//
|
|
// And yet it ALSO allows for different sizes and types. This
|
|
// seems paradoxical. How could both things be true?
|
|
//
|
|
// To accomplish this, the Zig compiler actually generates a
|
|
// separate copy of the function for every size/type combination!
|
|
// So in this case, three different functions will be generated
|
|
// for you, each with machine code that handles that specific
|
|
// data size and type.
|
|
//
|
|
// Please fix this function so that the 'size' parameter:
|
|
//
|
|
// 1) Is guaranteed to be known at compile time.
|
|
// 2) Sets the size of the array of type T (which is the
|
|
// sequence we're creating and returning).
|
|
//
|
|
fn makeSequence(comptime T: type, ??? size: usize) [???]T {
|
|
var sequence: [???]T = undefined;
|
|
var i: usize = 0;
|
|
|
|
while (i < size) : (i += 1) {
|
|
sequence[i] = @intCast(T, i) + 1;
|
|
}
|
|
|
|
return sequence;
|
|
}
|