exercises/exercises/033_iferror.zig
2022-01-01 02:20:26 +09:00

55 lines
1.3 KiB
Zig

//
// Let's revisit the very first error exercise. This time, we're going to
// look at an error-handling variation of the "if" statement.
//
// if (foo) |value| {
//
// // foo was NOT an error; value is the non-error value of foo
//
// } else |err| {
//
// // foo WAS an error; err is the error value of foo
//
// }
//
// We'll take it even further and use a switch statement to handle
// the error types.
//
// if (foo) |value| {
// ...
// } else |err| switch(err) {
// ...
// }
//
const MyNumberError = error{
TooBig,
TooSmall,
};
const std = @import("std");
pub fn main() void {
const nums = [_]u8{ 2, 3, 4, 5, 6 };
for (nums) |num| {
std.debug.print("{}", .{num});
const n = numberMaybeFail(num);
if (n) |value| {
std.debug.print("={}. ", .{value});
} else |err| switch (err) {
MyNumberError.TooBig => std.debug.print(">4. ", .{}),
// Please add a match for TooSmall here and have it print: "<4. "
}
}
std.debug.print("\n", .{});
}
// This time we'll have numberMaybeFail() return an error union rather
// than a straight error.
fn numberMaybeFail(n: u8) MyNumberError!u8 {
if (n > 4) return MyNumberError.TooBig;
if (n < 4) return MyNumberError.TooSmall;
return n;
}