Added temporary fix for unstable std from_str_radix method

This commit is contained in:
mitchmindtree 2015-04-24 15:17:42 +10:00
parent 3028d602e6
commit 63d2e79c1e
1 changed files with 150 additions and 4 deletions

View File

@ -43,14 +43,160 @@ macro_rules! int_trait_impl {
)*) )*)
} }
// FIXME: Temporary replacements for unstable ::std::num::ParseFloatError and
// ::std::num::FloatErrorKind. These can be removed once the std float implementation of
// from_str_radix stabilises.
pub enum FloatErrorKind { Empty, Invalid }
pub struct ParseFloatError { pub kind: FloatErrorKind }
// FIXME: This should be removed and replaced with the std implementation of from_str_radix once
// it is stabilised.
macro_rules! float_trait_impl { macro_rules! float_trait_impl {
($name:ident for $($t:ty)*) => ($( ($name:ident for $($t:ty)*) => ($(
impl $name for $t { impl $name for $t {
type FromStrRadixErr = ::std::num::ParseFloatError; type FromStrRadixErr = ParseFloatError;
fn from_str_radix(s: &str, radix: u32) fn from_str_radix(src: &str, radix: u32)
-> Result<Self, ::std::num::ParseFloatError> -> Result<Self, ParseFloatError>
{ {
Num::from_str_radix(s, radix) use self::FloatErrorKind::*;
use self::ParseFloatError as PFE;
// Special values
match src {
"inf" => return Ok(Float::infinity()),
"-inf" => return Ok(Float::neg_infinity()),
"NaN" => return Ok(Float::nan()),
_ => {},
}
fn slice_shift_char(src: &str) -> Option<(char, &str)> {
src.chars().nth(0).map(|ch| (ch, &src[1..]))
}
let (is_positive, src) = match slice_shift_char(src) {
None => return Err(PFE { kind: Empty }),
Some(('-', "")) => return Err(PFE { kind: Empty }),
Some(('-', src)) => (false, src),
Some((_, _)) => (true, src),
};
// The significand to accumulate
let mut sig = if is_positive { 0.0 } else { -0.0 };
// Necessary to detect overflow
let mut prev_sig = sig;
let mut cs = src.chars().enumerate();
// Exponent prefix and exponent index offset
let mut exp_info = None::<(char, usize)>;
// Parse the integer part of the significand
for (i, c) in cs.by_ref() {
match c.to_digit(radix) {
Some(digit) => {
// shift significand one digit left
sig = sig * (radix as $t);
// add/subtract current digit depending on sign
if is_positive {
sig = sig + ((digit as isize) as $t);
} else {
sig = sig - ((digit as isize) as $t);
}
// Detect overflow by comparing to last value, except
// if we've not seen any non-zero digits.
if prev_sig != 0.0 {
if is_positive && sig <= prev_sig
{ return Ok(Float::infinity()); }
if !is_positive && sig >= prev_sig
{ return Ok(Float::neg_infinity()); }
// Detect overflow by reversing the shift-and-add process
if is_positive && (prev_sig != (sig - digit as $t) / radix as $t)
{ return Ok(Float::infinity()); }
if !is_positive && (prev_sig != (sig + digit as $t) / radix as $t)
{ return Ok(Float::neg_infinity()); }
}
prev_sig = sig;
},
None => match c {
'e' | 'E' | 'p' | 'P' => {
exp_info = Some((c, i + 1));
break; // start of exponent
},
'.' => {
break; // start of fractional part
},
_ => {
return Err(PFE { kind: Invalid });
},
},
}
}
// If we are not yet at the exponent parse the fractional
// part of the significand
if exp_info.is_none() {
let mut power = 1.0;
for (i, c) in cs.by_ref() {
match c.to_digit(radix) {
Some(digit) => {
// Decrease power one order of magnitude
power = power / (radix as $t);
// add/subtract current digit depending on sign
sig = if is_positive {
sig + (digit as $t) * power
} else {
sig - (digit as $t) * power
};
// Detect overflow by comparing to last value
if is_positive && sig < prev_sig
{ return Ok(Float::infinity()); }
if !is_positive && sig > prev_sig
{ return Ok(Float::neg_infinity()); }
prev_sig = sig;
},
None => match c {
'e' | 'E' | 'p' | 'P' => {
exp_info = Some((c, i + 1));
break; // start of exponent
},
_ => {
return Err(PFE { kind: Invalid });
},
},
}
}
}
// Parse and calculate the exponent
let exp = match exp_info {
Some((c, offset)) => {
let base = match c {
'E' | 'e' if radix == 10 => 10.0,
'P' | 'p' if radix == 16 => 2.0,
_ => return Err(PFE { kind: Invalid }),
};
// Parse the exponent as decimal integer
let src = &src[offset..];
let (is_positive, exp) = match slice_shift_char(src) {
Some(('-', src)) => (false, src.parse::<usize>()),
Some(('+', src)) => (true, src.parse::<usize>()),
Some((_, _)) => (true, src.parse::<usize>()),
None => return Err(PFE { kind: Invalid }),
};
match (is_positive, exp) {
(true, Ok(exp)) => base.powi(exp as i32),
(false, Ok(exp)) => 1.0 / base.powi(exp as i32),
(_, Err(_)) => return Err(PFE { kind: Invalid }),
}
},
None => 1.0, // no exponent
};
Ok(sig * exp)
} }
} }
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