Number Formatter of Fixed Significance with Metric or Binary Prefix
Formats a given number in one of the three Signifix notations as defined below by determining
- the appropriate metric or binary prefix and
- the decimal mark position in such a way as to sustain a fixed number of four significant figures.
Three notations are defined,
- two with metric prefix, a default and an alternate, and
- one with binary prefix, a default only.
The two Signifix notations with metric prefix comprise
- a signed significand of four significant figures normalized from
±1.000to±999.9to cover the three powers of ten of a particular metric prefix with the three different decimal mark positions between these four figures, and - a metric prefix symbol or its placeholder in case of no prefix
- either being appended along with a whitespace as in
±1.234␣k, that is the default notation, - or replacing the decimal mark of the significand as in
±1k234, that is the alternate notation.
- either being appended along with a whitespace as in
In default notation the placeholder is another whitespace as in ±1.234␣␣
to align consistently, while in alternate notation it is a number sign as in
±1#234 to conspicuously separate the integer from the fractional part of
the significand. The locale-sensitive decimal mark defaults to a decimal
point. The plus sign of positive numbers is optional.
The one Signifix notation with binary prefix comprises
- a signed significand of four significant figures normalized from
±1.000over±999.9to±1 023to cover the four powers of ten of a particular binary prefix with the three different decimal mark positions between these four figures and a thousands separator, and - a binary prefix symbol or its placeholder in case of no prefix being
appended along with a whitespace as in
±1.234␣Ki.
To align consistently, the placeholder is another two whitespaces as in
±1.234␣␣␣. The locale-sensitive decimal mark defaults to a decimal point
while the locale-sensitive thousands separator defaults to a whitespace as
in ±1␣023␣Ki. The plus sign of positive numbers is optional.
This crate works since Rust 1.34 on stable channel. It is
on crates.io and can be used by adding
signifix to the dependencies in your project's Cargo.toml:
[dependencies]
signifix = "0.10"The Signifix notations result in a fixed number of characters preventing jumps to the left or right while making maximum use of their occupied space:
use std::convert::TryFrom;
use signifix::{metric, binary, Result};
let metric = |number| -> Result<(String, String)> {
let number = metric::Signifix::try_from(number)?;
Ok((format!("{}", number), format!("{:#}", number)))
};
let binary = |number| -> Result<String> {
let number = binary::Signifix::try_from(number)?;
Ok(format!("{}", number))
};
// Three different decimal mark positions covering the three powers of ten
// of a particular metric prefix.
assert_eq!(metric(1E-04), Ok(("100.0 µ".into(), "100µ0".into()))); // 3rd
assert_eq!(metric(1E-03), Ok(("1.000 m".into(), "1m000".into()))); // 1st
assert_eq!(metric(1E-02), Ok(("10.00 m".into(), "10m00".into()))); // 2nd
assert_eq!(metric(1E-01), Ok(("100.0 m".into(), "100m0".into()))); // 3rd
assert_eq!(metric(1E+00), Ok(("1.000 ".into(), "1#000".into()))); // 1st
assert_eq!(metric(1E+01), Ok(("10.00 ".into(), "10#00".into()))); // 2nd
assert_eq!(metric(1E+02), Ok(("100.0 ".into(), "100#0".into()))); // 3rd
assert_eq!(metric(1E+03), Ok(("1.000 k".into(), "1k000".into()))); // 1st
assert_eq!(metric(1E+04), Ok(("10.00 k".into(), "10k00".into()))); // 2nd
assert_eq!(metric(1E+05), Ok(("100.0 k".into(), "100k0".into()))); // 3rd
assert_eq!(metric(1E+06), Ok(("1.000 M".into(), "1M000".into()))); // 1st
// Three different decimal mark positions and a thousands separator covering
// the four powers of ten of a particular binary prefix.
assert_eq!(binary(1_024f64.powi(0) * 1E+00), Ok("1.000 ".into())); // 1st
assert_eq!(binary(1_024f64.powi(0) * 1E+01), Ok("10.00 ".into())); // 2nd
assert_eq!(binary(1_024f64.powi(0) * 1E+02), Ok("100.0 ".into())); // 3rd
assert_eq!(binary(1_024f64.powi(0) * 1E+03), Ok("1 000 ".into())); // 4th
assert_eq!(binary(1_024f64.powi(1) * 1E+00), Ok("1.000 Ki".into())); // 1st
assert_eq!(binary(1_024f64.powi(1) * 1E+01), Ok("10.00 Ki".into())); // 2nd
assert_eq!(binary(1_024f64.powi(1) * 1E+02), Ok("100.0 Ki".into())); // 3rd
assert_eq!(binary(1_024f64.powi(1) * 1E+03), Ok("1 000 Ki".into())); // 4th
assert_eq!(binary(1_024f64.powi(2) * 1E+00), Ok("1.000 Mi".into())); // 1st
// Rounding over prefixes is safe against floating-point inaccuracies.
assert_eq!(metric(999.949_999_999_999_8),
Ok(("999.9 ".into(), "999#9".into())));
assert_eq!(metric(999.949_999_999_999_9),
Ok(("1.000 k".into(), "1k000".into())));
assert_eq!(binary(1_023.499_999_999_999_94),
Ok("1 023 ".into()));
assert_eq!(binary(1_023.499_999_999_999_95),
Ok("1.000 Ki".into()));This is useful to smoothly refresh a transfer rate within a terminal:
use std::convert::TryFrom;
use std::f64;
use std::time::Duration;
use signifix::metric::{Signifix, Error, DEF_MIN_LEN};
let transfer_rate = |bytes: u64, duration: Duration| -> String {
let seconds = duration.as_secs() as f64
+ duration.subsec_nanos() as f64 * 1E-09;
let bytes_per_second = bytes as f64 / seconds;
let unit = "B/s";
let rate = match Signifix::try_from(bytes_per_second) {
Ok(rate) => if rate.factor() < 1E+00 {
" - slow - ".into() // instead of mB/s, µB/s, ...
} else {
format!("{}{}", rate, unit) // normal rate
},
Err(case) => match case {
Error::OutOfLowerBound(rate) => if rate == 0f64 {
" - idle - " // no progress at all
} else {
" - slow - " // almost no progress
},
Error::OutOfUpperBound(rate) => if rate == f64::INFINITY {
" - ---- - " // zero nanoseconds
} else {
" - fast - " // awkwardly fast
},
Error::Nan => " - ---- - ", // zero bytes in zero nanoseconds
}.into(),
};
debug_assert_eq!(rate.chars().count(),
DEF_MIN_LEN + unit.chars().count());
rate
};
assert_eq!(transfer_rate(42_667, Duration::from_secs(300)), "142.2 B/s");
assert_eq!(transfer_rate(42_667, Duration::from_secs(030)), "1.422 kB/s");
assert_eq!(transfer_rate(42_667, Duration::from_secs(003)), "14.22 kB/s");
assert_eq!(transfer_rate(00_001, Duration::from_secs(003)), " - slow - ");
assert_eq!(transfer_rate(00_000, Duration::from_secs(003)), " - idle - ");
assert_eq!(transfer_rate(42_667, Duration::from_secs(000)), " - ---- - ");Or to monitor a measured quantity like an electrical current including its direction with positive numbers being padded to align with negative ones:
use std::convert::TryFrom;
use signifix::metric::{Signifix, Result, DEF_MAX_LEN};
let measured_amps = |amps| -> Result<String> {
if let Some(amps) = amps {
Signifix::try_from(amps)
.map(|amps| format!("{:>1$}A", amps, DEF_MAX_LEN))
} else {
Ok(" 0 A".into())
}
};
assert_eq!(measured_amps(Some( 1.476E-06)), Ok(" 1.476 µA".into()));
assert_eq!(measured_amps(None), Ok(" 0 A".into()));
assert_eq!(measured_amps(Some(-2.927E-06)), Ok("-2.927 µA".into()));While to visualize a change in file size, a plus sign might be preferred for positive numbers:
use std::convert::TryFrom;
use signifix::metric::{Signifix, Error, Result};
let filesize_diff = |curr, prev| -> Result<String> {
Signifix::try_from(curr - prev).map(|diff| format!("{:+#}", diff))
.or_else(|case| if case == Error::OutOfLowerBound(0f64)
{ Ok("=const".into()) } else { Err(case) })
};
assert_eq!(filesize_diff(78_346, 57_393), Ok("+20k95".into()));
assert_eq!(filesize_diff(93_837, 93_837), Ok("=const".into()));
assert_eq!(filesize_diff(27_473, 36_839), Ok("-9k366".into()));The binary prefix instead suits well to visualize quantities being multiples of powers of two, such as memory boundaries due to binary addressing:
use std::convert::TryFrom;
use signifix::binary::{Signifix, Error, Result};
let boundary_stat = |used: u64, size: u64| -> Result<String> {
if used == 0 {
let size = Signifix::try_from(size)?;
return Ok(format!(" 0 B ( 0 %) of {}B", size));
}
let p100 = Signifix::try_from(used as f64 / size as f64 * 100.0)
.map(|p100| format!("{:.*} %", p100.exponent(), p100.significand()))
.or_else(|error| if let Error::OutOfLowerBound(_) = error
{ Ok(" < 1 %".into()) } else { Err(error) })?;
let used = Signifix::try_from(used)?;
let size = Signifix::try_from(size)?;
Ok(format!("{}B ({}) of {}B", used, p100, size))
};
assert_eq!(boundary_stat(0_000u64.pow(1), 1_024u64.pow(3)),
Ok(" 0 B ( 0 %) of 1.000 GiB".into()));
assert_eq!(boundary_stat(1_024u64.pow(2), 1_024u64.pow(3)),
Ok("1.000 MiB ( < 1 %) of 1.000 GiB".into()));
assert_eq!(boundary_stat(3_292u64.pow(2), 1_024u64.pow(3)),
Ok("10.34 MiB (1.009 %) of 1.000 GiB".into()));
assert_eq!(boundary_stat(8_192u64.pow(2), 1_024u64.pow(3)),
Ok("64.00 MiB (6.250 %) of 1.000 GiB".into()));
assert_eq!(boundary_stat(1_000u64.pow(3), 1_024u64.pow(3)),
Ok("953.7 MiB (93.13 %) of 1.000 GiB".into()));
assert_eq!(boundary_stat(1_024u64.pow(3), 1_024u64.pow(3)),
Ok("1.000 GiB (100.0 %) of 1.000 GiB".into()));Until there is a recommended and possibly implicit localization system for
Rust, explicit localization can be achieved by wrapping the Signifix type
into a locale-sensitive newtype which implements the Display trait via the
Signifix::fmt() method:
use std::convert::TryFrom;
use signifix::binary::{Signifix, Result};
struct SignifixSi(Signifix); // English SI style (default)
struct SignifixEn(Signifix); // English locale (whitespace -> comma)
struct SignifixDe(Signifix); // German locale (comma <-> point)
impl std::fmt::Display for SignifixSi {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
std::fmt::Display::fmt(&self.0, f)
}
}
impl std::fmt::Display for SignifixEn {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
self.0.fmt(f, ".", ",")
}
}
impl std::fmt::Display for SignifixDe {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
self.0.fmt(f, ",", ".")
}
}
let localizations = |number| -> Result<(String, String, String)> {
Signifix::try_from(number).map(|number| (
format!("{}", SignifixSi(number)),
format!("{}", SignifixEn(number)),
format!("{}", SignifixDe(number)),
))
};
assert_eq!(localizations(999.9f64 * 1_024f64),
Ok(("999.9 Ki".into(), "999.9 Ki".into(), "999,9 Ki".into())));
assert_eq!(localizations(1_000f64 * 1_024f64),
Ok(("1 000 Ki".into(), "1,000 Ki".into(), "1.000 Ki".into())));Customization can be achieved by extracting information from the Signifix
type via its methods:
use std::convert::TryFrom;
use signifix::metric::{Signifix, Result};
struct SignifixTable<'a>(&'a[Signifix]);
impl<'a> std::fmt::Display for SignifixTable<'a> {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
f.pad(" Int Fra 10³\n")?;
f.pad("---- ---- ----\n")?;
for entry in self.0 {
let (integer, fractional) = entry.parts();
f.pad(&format!("{:4} {:<3} {:2}\n",
integer, fractional, entry.prefix() as i32 - 8))?;
}
Ok(())
}
}
let customization = |entries: &[_]| -> Result<String> {
let mut table = Vec::with_capacity(entries.len());
for entry in entries {
table.push(Signifix::try_from(*entry)?);
}
Ok(SignifixTable(&table).to_string())
};
assert_eq!(customization(&[
1.234E-06,
12.34E+00,
-123.4E+24,
]), Ok(concat!(
" Int Fra 10³\n",
"---- ---- ----\n",
" 1 234 -2\n",
" 12 34 0\n",
"-123 4 8\n",
).into()));Copyright (c) 2016-2019 Rouven Spreckels n3vu0r@qu1x.org
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