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65 | //
// 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!
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