diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig index c9ba3b347060..6dbef5db67fe 100644 --- a/lib/std/fmt.zig +++ b/lib/std/fmt.zig @@ -560,13 +560,25 @@ fn formatFloatValue( options: FormatOptions, writer: anytype, ) !void { + // this buffer should be enough to display all decimal places of a decimal f64 number. + var buf: [512]u8 = undefined; + var buf_stream = std.io.fixedBufferStream(&buf); + if (fmt.len == 0 or comptime std.mem.eql(u8, fmt, "e")) { - return formatFloatScientific(value, options, writer); + formatFloatScientific(value, options, buf_stream.writer()) catch |err| switch (err) { + error.NoSpaceLeft => unreachable, + else => |e| return e, + }; } else if (comptime std.mem.eql(u8, fmt, "d")) { - return formatFloatDecimal(value, options, writer); + formatFloatDecimal(value, options, buf_stream.writer()) catch |err| switch (err) { + error.NoSpaceLeft => unreachable, + else => |e| return e, + }; } else { @compileError("Unknown format string: '" ++ fmt ++ "'"); } + + return formatBuf(buf_stream.getWritten(), options, writer); } pub fn formatText( @@ -1791,3 +1803,17 @@ test "padding" { try testFmt("==================Filled", "{:=>24}", .{"Filled"}); try testFmt(" Centered ", "{:^24}", .{"Centered"}); } + +test "decimal float padding" { + var number: f32 = 3.1415; + try testFmt("left-pad: **3.141\n", "left-pad: {d:*>7.3}\n", .{number}); + try testFmt("center-pad: *3.141*\n", "center-pad: {d:*^7.3}\n", .{number}); + try testFmt("right-pad: 3.141**\n", "right-pad: {d:*<7.3}\n", .{number}); +} + +test "sci float padding" { + var number: f32 = 3.1415; + try testFmt("left-pad: **3.141e+00\n", "left-pad: {e:*>11.3}\n", .{number}); + try testFmt("center-pad: *3.141e+00*\n", "center-pad: {e:*^11.3}\n", .{number}); + try testFmt("right-pad: 3.141e+00**\n", "right-pad: {e:*<11.3}\n", .{number}); +}