root.zig - dicer - dicer: Dice roll app

root.zig (1141B)
      1 const std = @import("std");
      2 const testing = std.testing;
      3 
      4 pub fn dicer(args: anytype, wtr: anytype) !void {
      5     doDicer(args, wtr) catch |e| switch (e) {
      6         error.MissingArg, error.InvalidCharacter => {
      7             try printUsage(wtr);
      8             return;
      9         },
     10         else => return e,
     11     };
     12 }
     13 
     14 fn doDicer(args: anytype, wtr: anytype) !void {
     15     const dice_str = args.next() orelse return error.MissingArg;
     16     var spl = std.mem.splitScalar(u8, dice_str, 'd');
     17     const count = try std.fmt.parseInt(u64, spl.first(), 10);
     18     const sides = try std.fmt.parseInt(u64, spl.next() orelse "6", 10);
     19 
     20     try wtr.writeAll("Dice roll: ");
     21     var total: u64 = 0;
     22     for (0..count) |_| {
     23         const res = roll(sides);
     24         try std.fmt.format(wtr, "{} ", .{res});
     25         total += res;
     26     }
     27     try std.fmt.format(wtr, " total: {}", .{total});
     28     try wtr.writeByte('\n');
     29 }
     30 
     31 fn roll(dsize: u64) u64 {
     32     return (std.crypto.random.int(u64) % dsize) + 1;
     33 }
     34 
     35 fn printUsage(wtr: anytype) !void {
     36     try std.fmt.format(wtr,
     37         \\Usage: 
     38         \\ dicer XdY
     39         \\
     40         \\Rolls X dice with Y
     41         \\
     42     , .{});
     43 }