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Diffstat (limited to 'exercises')
| -rw-r--r-- | exercises/073_comptime8.zig | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/exercises/073_comptime8.zig b/exercises/073_comptime8.zig new file mode 100644 index 0000000..6828f55 --- /dev/null +++ b/exercises/073_comptime8.zig @@ -0,0 +1,65 @@ +// +// 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! |