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Implement format code e & E for floats and ints

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This commit is contained in:
Abe
2020-03-06 18:02:45 -07:00
parent 8bde882a39
commit 4c72a3c853
2 changed files with 43 additions and 12 deletions
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21
tests/snippets/strings.py
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@@ -450,3 +450,24 @@ assert '{:%}'.format(float('inf')) == 'inf%'
assert '{:.2%}'.format(float('inf')) == 'inf%'
with AssertRaises(ValueError, msg='Invalid format specifier'):
f'{10.0:%3}'
# Test e & E formatting
assert '{:e}'.format(10) == '1.000000e+01'
assert '{:.2e}'.format(11) == '1.10e+01'
assert '{:e}'.format(10.0) == '1.000000e+01'
assert '{:e}'.format(-10.0) == '-1.000000e+01'
assert '{:.2e}'.format(10.0) == '1.00e+01'
assert '{:.2e}'.format(-10.0) == '-1.00e+01'
assert '{:.2e}'.format(10.1) == '1.01e+01'
assert '{:.2e}'.format(-10.1) == '-1.01e+01'
assert '{:.2e}'.format(10.001) == '1.00e+01'
assert '{:.4e}'.format(100.234) == '1.0023e+02'
assert '{:.5e}'.format(100.234) == '1.00234e+02'
assert '{:.2E}'.format(10.0) == '1.00E+01'
assert '{:.2E}'.format(-10.0) == '-1.00E+01'
assert '{:e}'.format(float('nan')) == 'nan'
assert '{:e}'.format(float('-nan')) == 'nan'
assert '{:E}'.format(float('nan')) == 'NAN'
assert '{:e}'.format(float('inf')) == 'inf'
assert '{:e}'.format(float('-inf')) == '-inf'
assert '{:E}'.format(float('inf')) == 'INF'

34
vm/src/format.rs
View File

@@ -272,6 +272,16 @@ fn parse_format_spec(text: &str) -> Result<FormatSpec, &'static str> {
})
}
// Formats floats into Python style exponent notation, by first formatting in Rust style
// exponent notation (`1.0000e0`), then convert to Python style (`1.0000e+00`).
fn format_float_as_exponent(precision: usize, magnitude: f64, separator: &str) -> String {
let r_exp = format!("{:.*e}", precision, magnitude);
let mut parts = r_exp.splitn(2, 'e');
let base = parts.next().unwrap();
let exponent = parts.next().unwrap().parse::<i64>().unwrap();
format!("{}{}+{:02}", base, separator, exponent)
}
impl FormatSpec {
pub fn parse(text: &str) -> Result<FormatSpec, &'static str> {
parse_format_spec(text)
@@ -370,12 +380,16 @@ impl FormatSpec {
Some(FormatType::GeneralFormatLower) => {
Err("Format code 'g' for object of type 'float' not implemented yet")
}
Some(FormatType::ExponentUpper) => {
Err("Format code 'E' for object of type 'float' not implemented yet")
}
Some(FormatType::ExponentLower) => {
Err("Format code 'e' for object of type 'float' not implemented yet")
}
Some(FormatType::ExponentUpper) => match magnitude {
magnitude if magnitude.is_nan() => Ok("NAN".to_owned()),
magnitude if magnitude.is_infinite() => Ok("INF".to_owned()),
_ => Ok(format_float_as_exponent(precision, magnitude, "E")),
},
Some(FormatType::ExponentLower) => match magnitude {
magnitude if magnitude.is_nan() => Ok("nan".to_owned()),
magnitude if magnitude.is_infinite() => Ok("inf".to_owned()),
_ => Ok(format_float_as_exponent(precision, magnitude, "e")),
},
Some(FormatType::Percentage) => match magnitude {
magnitude if magnitude.is_nan() => Ok("nan%".to_owned()),
magnitude if magnitude.is_infinite() => Ok("inf%".to_owned()),
@@ -443,14 +457,10 @@ impl FormatSpec {
Some(FormatType::GeneralFormatLower) => {
Err("Unknown format code 'g' for object of type 'int'")
}
Some(FormatType::ExponentUpper) => {
Err("Unknown format code 'E' for object of type 'int'")
}
Some(FormatType::ExponentLower) => {
Err("Unknown format code 'e' for object of type 'int'")
}
Some(FormatType::FixedPointUpper)
| Some(FormatType::FixedPointLower)
| Some(FormatType::ExponentUpper)
| Some(FormatType::ExponentLower)
| Some(FormatType::Percentage) => match num.to_f64() {
Some(float) => return self.format_float(float),
_ => Err("Unable to convert int to float"),