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//
// Another common problem is a block of code that could exit in multiple
// places due to an error - but that needs to do something before it
// exits (typically to clean up after itself).
//
// An "errdefer" is a defer that only runs if the block exits with an error:
//
// {
// errdefer cleanup();
// try canFail();
// }
//
// The cleanup() function is called ONLY if the "try" statement returns an
// error produced by canFail().
//
const std = @import("std");
var counter: u32 = 0;
const MyErr = error{ GetFail, IncFail };
pub fn main() void {
// We simply quit the entire program if we fail to get a number:
var a: u32 = makeNumber() catch return;
var b: u32 = makeNumber() catch return;
std.debug.print("Numbers: {}, {}\n", .{ a, b });
}
fn makeNumber() MyErr!u32 {
std.debug.print("Getting number...", .{});
// Please make the "failed" message print ONLY if the makeNumber()
// function exits with an error:
std.debug.print("failed!\n", .{});
var num = try getNumber(); // <-- This could fail!
num = try increaseNumber(num); // <-- This could ALSO fail!
std.debug.print("got {}. ", .{num});
return num;
}
fn getNumber() MyErr!u32 {
// I _could_ fail...but I don't!
return 4;
}
fn increaseNumber(n: u32) MyErr!u32 {
// I fail after the first time you run me!
if (counter > 0) return MyErr.IncFail;
// Sneaky, weird global stuff.
counter += 1;
return n + 1;
}
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