std.fmt in Zig

Format into a stack buffer and parse back out — no allocator in sight.

const std = @import("std");

pub fn main() !void {
    // bufPrint formats into a stack buffer -- no allocator involved.
    var buf: [48]u8 = undefined;
    const line = try std.fmt.bufPrint(&buf, "day {d} mean {d:.2}", .{
        3, 68.14,
    });
    std.debug.print("built: [{s}]\n", .{line});

    // parseInt and parseFloat go the other way.
    const day = try std.fmt.parseInt(u8, line[4..5], 10);
    const mean = try std.fmt.parseFloat(f32, "68.14");
    std.debug.print("parsed back: day {d}, mean {d:.2}\n", .{ day, mean });
}

How it works

1. bufPrint writes into buf and returns the slice it used.
2. {d:.2} fixes the decimals the same way in every print.
3. parseInt and parseFloat return error unions, unwrapped here with try.

Keywords and builtins used here

• const
• f32
• fn
• pub
• try
• u8
• var
• void

The run, in numbers

Lines

15

Characters to type

494

Tokens

133

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 123 seconds.

Type this snippet

Step 2 of 3 in The standard library, step 23 of 27 in Language basics.

← Previous Next →