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Diffstat (limited to 'exercises')
| -rw-r--r-- | exercises/064_builtins.zig | 74 |
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diff --git a/exercises/064_builtins.zig b/exercises/064_builtins.zig new file mode 100644 index 0000000..a9761c2 --- /dev/null +++ b/exercises/064_builtins.zig @@ -0,0 +1,74 @@ +// +// The Zig compiler provides "builtin" functions. You've already +// gotten used to seeing an @import() at the top of every +// Ziglings exercise. +// +// We've also seen @intCast() in "016_for2.zig", "058_quiz7.zig"; +// and @enumToInt() in "036_enums2.zig". +// +// Builtins are special because they are intrinsic to the Zig +// language itself (as opposed to being provided in the standard +// library). They are also special because they can provide +// functionality that is only possible with help from the +// compiler, such as type introspection (the ability to examine +// type properties from within a program). +// +// Zig currently contains 101 builtin functions. We're certainly +// not going to cover them all, but we can look at some +// interesting ones. +// +// Before we begin, know that many builtin functions have +// parameters marked as "comptime". It's probably fairly clear +// what we mean when we say that these parameters need to be +// "known at compile time." But rest assured we'll be doing the +// "comptime" subject real justice soon. +// +const print = @import("std").debug.print; + +pub fn main() void { + // The first builtin, alphabetically, is: + // + // @addWithOverflow(comptime T: type, a: T, b: T, result: *T) bool + // * 'T' will be the type of the other parameters. + // * 'a' and 'b' are numbers of the type T. + // * 'result' is a pointer to space you're providing of type T. + // * The return value is true if the addition resulted in a + // value over or under the capacity of type T. + // + // Let's try it with a tiny 4-bit integer size to make it clear: + const a: u4 = 0b1101; + const b: u4 = 0b0101; + var my_result: u4 = undefined; + var overflowed: bool = undefined; + overflowed = @addWithOverflow(u4, a, b, &my_result); + // + // The print() below will produce: "1101 + 0101 = 0010 (true)". + // Let's make sense of this answer by counting up from 1101: + // + // Overflowed? + // 1101 + 1 = 1110 No. + // 1110 + 1 = 1111 No. + // 1111 + 1 = 0000 Yes! (Real answer is 10000) + // 0000 + 1 = 0001 Yes! + // 0001 + 1 = 0010 Yes! + // + // Also, check out our fancy formatting! b:0>4 means, "print + // as a binary number, zero-pad right-aligned four digits." + print("{b:0>4} + {b:0>4} = {b:0>4} ({})", .{a, b, my_result, overflowed}); + + print(". Furthermore, ", .{}); + + // Here's a fun one: + // + // @bitReverse(comptime T: type, integer: T) T + // * 'T' will be the type of the input and output. + // * 'integer' is the value to reverse. + // * The return value will be the same type with the + // value's bits reversed! + // + // Now it's your turn. See if you can fix this attempt to use + // this builtin to reverse the bits of a u8 integer. + const input: u8 = 0b11110000; + const tupni: u8 = @bitReverse(input); + print("{b:0>8} backwards is {b:0>8}.\n", .{input}); +} |