Function formatFloat [src]

Alias for std.fmt.format_float.formatFloat

Format a floating-point value and write it to buffer. Returns a slice to the buffer containing the string representation. Full precision is the default. Any full precision float can be reparsed with std.fmt.parseFloat unambiguously. Scientific mode is recommended generally as the output is more compact and any type can be written in full precision using a buffer of only min_buffer_size. When printing full precision decimals, use bufferSize to get the required space. It is recommended to bound decimal output with a fixed precision to reduce the required buffer size.

Prototype

pub fn formatFloat(buf: []u8, v_: anytype, options: FormatOptions) FormatError![]const u8

Parameters

buf: []u8options: FormatOptions

Possible Errors

BufferTooSmall

Source

  pub fn formatFloat(buf: []u8, v_: anytype, options: FormatOptions) FormatError![]const u8 {
    const v = switch (@TypeOf(v_)) {
        // comptime_float internally is a f128; this preserves precision.
        comptime_float => @as(f128, v_),
        else => v_,
    };

    const T = @TypeOf(v);
    comptime std.debug.assert(@typeInfo(T) == .float);
    const I = @Type(.{ .int = .{ .signedness = .unsigned, .bits = @bitSizeOf(T) } });

    const DT = if (@bitSizeOf(T) <= 64) u64 else u128;
    const tables = switch (DT) {
        u64 => if (@import("builtin").mode == .ReleaseSmall) &Backend64_TablesSmall else &Backend64_TablesFull,
        u128 => &Backend128_Tables,
        else => unreachable,
    };

    const has_explicit_leading_bit = std.math.floatMantissaBits(T) - std.math.floatFractionalBits(T) != 0;
    const d = binaryToDecimal(DT, @as(I, @bitCast(v)), std.math.floatMantissaBits(T), std.math.floatExponentBits(T), has_explicit_leading_bit, tables);

    return switch (options.mode) {
        .scientific => formatScientific(DT, buf, d, options.precision),
        .decimal => formatDecimal(DT, buf, d, options.precision),
    };
}  