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//
// We've seen that Zig implicitly performs some evaluations at
// compile time. But sometimes you'll want to explicitly request
// compile time evaluation. For that, we have a new keyword:
//
// . . . o . . * . . .
// . * | . . . . . . * . .
// --o-- comptime * | .. .
// * | * . . . . --*-- . * .
// . . . . . . . . . | . . .
//
// When placed before a variable declaration, 'comptime'
// guarantees that every usage of that variable will be performed
// at compile time.
//
// As a simple example, compare these two statements:
//
// var bar1 = 5; // ERROR!
// comptime var bar2 = 5; // OKAY!
//
// The first one gives us an error because Zig assumes mutable
// identifiers (declared with 'var') will be used at runtime and
// we have not assigned a runtime type (like u8 or f32). Trying
// to use a comptime_int of undetermined size at runtime is
// a MEMORY CRIME and you are UNDER ARREST.
//
// The second one is is okay because we've told Zig that 'bar2'
// is a compile time variable. Zig will help us ensure this is true
// and let us know if we make a mistake.
//
const print = @import("std").debug.print;
pub fn main() void {
//
// In this contrived example, we've decided to allocate some
// arrays using a variable count! But something's missing...
//
var count = 0;
count += 1;
var a1: [count]u8 = .{'A'} ** count;
count += 1;
var a2: [count]u8 = .{'B'} ** count;
count += 1;
var a3: [count]u8 = .{'C'} ** count;
count += 1;
var a4: [count]u8 = .{'D'} ** count;
print("{s} {s} {s} {s}\n", .{a1, a2, a3, a4});
// Builtin BONUS!
//
// The @compileLog() builtin is like a print statement that
// ONLY operates at compile time. The Zig compiler treats
// @compileLog() calls as errors, so you'll want to use them
// temporarily to debug compile time logic.
//
// Try uncommenting this line and playing around with it
// (copy it, move it) to see what it does:
//@compileLog("Count at compile time: ", count);
}
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