ziglings/exercises/033_iferror.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. ", .{}),
      MyNumberError.TooSmall => 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;
}