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Support precision in fmt_scientific_notation #555

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merged 3 commits into from
Nov 24, 2022
Merged

Support precision in fmt_scientific_notation #555

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7cb9804
Support precision in `fmt_scientific_notation`
nicksenger Oct 11, 2022
543c1e4
fix: move test
nicksenger Oct 18, 2022
73fed3a
fmt: collapse if else
nicksenger Nov 17, 2022
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22 changes: 18 additions & 4 deletions src/str.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -102,16 +102,30 @@ pub(crate) fn fmt_scientific_notation(
// point in the right place and adjust the exponent accordingly.

let len = chars.len();
let precision = f.precision().unwrap_or(0);
let mut rep;
if len > 1 {
if chars.iter().take(len - 1).all(|c| *c == '0') {
// Chomp off the zero's.
if precision == 0 && chars.iter().take(len - 1).all(|c| *c == '0') {
rep = chars.iter().skip(len - 1).collect::<String>();
} else {
chars.insert(len - 1, '.');
rep = chars.iter().rev().collect::<String>();
if precision > 0 || f.precision().is_none() {
chars.insert(len - 1, '.');
}
rep = chars
.iter()
.rev()
.chain(core::iter::repeat(&'0'))
.take(f.precision().map(|p| if p == 0 { 1 } else { 2 + p }).unwrap_or(len + 1))
.collect::<String>();
}
exponent += (len - 1) as isize;
} else if precision > 0 {
chars.push('.');
rep = chars
.iter()
.chain(core::iter::repeat(&'0'))
.take(2 + precision)
.collect::<String>();
} else {
rep = chars.iter().collect::<String>();
}
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89 changes: 89 additions & 0 deletions tests/decimal_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -319,6 +319,95 @@ fn it_formats_lower_exp_padding() {
}
}

#[test]
fn it_formats_scientific_precision() {
for (num, scale, expected_no_precision, expected_precision) in [
(
123456,
10,
"1.23456e-5",
[
"1e-5",
"1.2e-5",
"1.23e-5",
"1.234e-5",
"1.2345e-5",
"1.23456e-5",
"1.234560e-5",
"1.2345600e-5",
],
),
(
123456,
0,
"1.23456e5",
[
"1e5",
"1.2e5",
"1.23e5",
"1.234e5",
"1.2345e5",
"1.23456e5",
"1.234560e5",
"1.2345600e5",
],
),
(
1,
0,
"1e0",
[
"1e0",
"1.0e0",
"1.00e0",
"1.000e0",
"1.0000e0",
"1.00000e0",
"1.000000e0",
"1.0000000e0",
],
),
(
-123456,
10,
"-1.23456e-5",
[
"-1e-5",
"-1.2e-5",
"-1.23e-5",
"-1.234e-5",
"-1.2345e-5",
"-1.23456e-5",
"-1.234560e-5",
"-1.2345600e-5",
],
),
(
-100000,
10,
"-1e-5",
[
"-1e-5",
"-1.0e-5",
"-1.00e-5",
"-1.000e-5",
"-1.0000e-5",
"-1.00000e-5",
"-1.000000e-5",
"-1.0000000e-5",
],
),
] {
assert_eq!(format!("{:e}", Decimal::new(num, scale)), expected_no_precision);
for i in 0..expected_precision.len() {
assert_eq!(
format!("{:.prec$e}", Decimal::new(num, scale), prec = i),
expected_precision[i]
);
}
}
}

// Negation
#[test]
fn it_negates_decimals() {
Expand Down