65 lines
1.7 KiB
Zig
65 lines
1.7 KiB
Zig
//
|
|
// As a matter of fact, you can put 'comptime' in front of any
|
|
// expression to force it to be run at compile time.
|
|
//
|
|
// Execute a function:
|
|
//
|
|
// comptime llama();
|
|
//
|
|
// Get a value:
|
|
//
|
|
// bar = comptime baz();
|
|
//
|
|
// Execute a whole block:
|
|
//
|
|
// comptime {
|
|
// bar = baz + biff();
|
|
// llama(bar);
|
|
// }
|
|
//
|
|
// Get a value from a block:
|
|
//
|
|
// var llama = comptime bar: {
|
|
// const baz = biff() + bonk();
|
|
// break :bar baz;
|
|
// }
|
|
//
|
|
const print = @import("std").debug.print;
|
|
|
|
const llama_count = 5;
|
|
const llamas = [llama_count]u32{ 5, 10, 15, 20, 25 };
|
|
|
|
pub fn main() void {
|
|
// We meant to fetch the last llama. Please fix this simple
|
|
// mistake so the assertion no longer fails.
|
|
const my_llama = getLlama(5);
|
|
|
|
print("My llama value is {}.\n", .{my_llama});
|
|
}
|
|
|
|
fn getLlama(i: usize) u32 {
|
|
// We've put a guard assert() at the top of this function to
|
|
// prevent mistakes. The 'comptime' keyword here means that
|
|
// the mistake will be caught when we compile!
|
|
//
|
|
// Without 'comptime', this would still work, but the
|
|
// assertion would fail at runtime with a PANIC, and that's
|
|
// not as nice.
|
|
//
|
|
// Unfortunately, we're going to get an error right now
|
|
// because the 'i' parameter needs to be guaranteed to be
|
|
// known at compile time. What can you do with the 'i'
|
|
// parameter above to make this so?
|
|
comptime assert(i < llama_count);
|
|
|
|
return llamas[i];
|
|
}
|
|
|
|
// Fun fact: this assert() function is identical to
|
|
// std.debug.assert() from the Zig Standard Library.
|
|
fn assert(ok: bool) void {
|
|
if (!ok) unreachable;
|
|
}
|
|
//
|
|
// Bonus fun fact: I accidentally replaced all instances of 'foo'
|
|
// with 'llama' in this exercise and I have no regrets!
|