Added temporary fix for unstable std from_str_radix method
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mitchmindtree
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3028d602e6
commit
63d2e79c1e
154
src/traits.rs
154
src/traits.rs
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@ -43,14 +43,160 @@ macro_rules! int_trait_impl {
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)*)
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}
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// FIXME: Temporary replacements for unstable ::std::num::ParseFloatError and
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// ::std::num::FloatErrorKind. These can be removed once the std float implementation of
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// from_str_radix stabilises.
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pub enum FloatErrorKind { Empty, Invalid }
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pub struct ParseFloatError { pub kind: FloatErrorKind }
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// FIXME: This should be removed and replaced with the std implementation of from_str_radix once
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// it is stabilised.
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macro_rules! float_trait_impl {
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($name:ident for $($t:ty)*) => ($(
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impl $name for $t {
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type FromStrRadixErr = ::std::num::ParseFloatError;
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fn from_str_radix(s: &str, radix: u32)
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-> Result<Self, ::std::num::ParseFloatError>
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type FromStrRadixErr = ParseFloatError;
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fn from_str_radix(src: &str, radix: u32)
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-> Result<Self, ParseFloatError>
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{
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Num::from_str_radix(s, radix)
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use self::FloatErrorKind::*;
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use self::ParseFloatError as PFE;
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// Special values
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match src {
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"inf" => return Ok(Float::infinity()),
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"-inf" => return Ok(Float::neg_infinity()),
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"NaN" => return Ok(Float::nan()),
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_ => {},
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}
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fn slice_shift_char(src: &str) -> Option<(char, &str)> {
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src.chars().nth(0).map(|ch| (ch, &src[1..]))
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}
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let (is_positive, src) = match slice_shift_char(src) {
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None => return Err(PFE { kind: Empty }),
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Some(('-', "")) => return Err(PFE { kind: Empty }),
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Some(('-', src)) => (false, src),
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Some((_, _)) => (true, src),
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};
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// The significand to accumulate
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let mut sig = if is_positive { 0.0 } else { -0.0 };
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// Necessary to detect overflow
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let mut prev_sig = sig;
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let mut cs = src.chars().enumerate();
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// Exponent prefix and exponent index offset
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let mut exp_info = None::<(char, usize)>;
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// Parse the integer part of the significand
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for (i, c) in cs.by_ref() {
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match c.to_digit(radix) {
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Some(digit) => {
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// shift significand one digit left
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sig = sig * (radix as $t);
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// add/subtract current digit depending on sign
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if is_positive {
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sig = sig + ((digit as isize) as $t);
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} else {
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sig = sig - ((digit as isize) as $t);
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}
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// Detect overflow by comparing to last value, except
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// if we've not seen any non-zero digits.
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if prev_sig != 0.0 {
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if is_positive && sig <= prev_sig
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{ return Ok(Float::infinity()); }
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if !is_positive && sig >= prev_sig
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{ return Ok(Float::neg_infinity()); }
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// Detect overflow by reversing the shift-and-add process
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if is_positive && (prev_sig != (sig - digit as $t) / radix as $t)
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{ return Ok(Float::infinity()); }
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if !is_positive && (prev_sig != (sig + digit as $t) / radix as $t)
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{ return Ok(Float::neg_infinity()); }
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}
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prev_sig = sig;
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},
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None => match c {
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'e' | 'E' | 'p' | 'P' => {
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exp_info = Some((c, i + 1));
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break; // start of exponent
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},
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'.' => {
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break; // start of fractional part
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},
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_ => {
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return Err(PFE { kind: Invalid });
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},
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},
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}
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}
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// If we are not yet at the exponent parse the fractional
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// part of the significand
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if exp_info.is_none() {
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let mut power = 1.0;
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for (i, c) in cs.by_ref() {
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match c.to_digit(radix) {
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Some(digit) => {
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// Decrease power one order of magnitude
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power = power / (radix as $t);
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// add/subtract current digit depending on sign
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sig = if is_positive {
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sig + (digit as $t) * power
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} else {
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sig - (digit as $t) * power
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};
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// Detect overflow by comparing to last value
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if is_positive && sig < prev_sig
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{ return Ok(Float::infinity()); }
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if !is_positive && sig > prev_sig
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{ return Ok(Float::neg_infinity()); }
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prev_sig = sig;
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},
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None => match c {
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'e' | 'E' | 'p' | 'P' => {
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exp_info = Some((c, i + 1));
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break; // start of exponent
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},
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_ => {
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return Err(PFE { kind: Invalid });
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},
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},
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}
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}
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}
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// Parse and calculate the exponent
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let exp = match exp_info {
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Some((c, offset)) => {
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let base = match c {
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'E' | 'e' if radix == 10 => 10.0,
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'P' | 'p' if radix == 16 => 2.0,
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_ => return Err(PFE { kind: Invalid }),
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};
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// Parse the exponent as decimal integer
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let src = &src[offset..];
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let (is_positive, exp) = match slice_shift_char(src) {
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Some(('-', src)) => (false, src.parse::<usize>()),
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Some(('+', src)) => (true, src.parse::<usize>()),
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Some((_, _)) => (true, src.parse::<usize>()),
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None => return Err(PFE { kind: Invalid }),
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};
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match (is_positive, exp) {
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(true, Ok(exp)) => base.powi(exp as i32),
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(false, Ok(exp)) => 1.0 / base.powi(exp as i32),
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(_, Err(_)) => return Err(PFE { kind: Invalid }),
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}
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},
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None => 1.0, // no exponent
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};
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Ok(sig * exp)
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}
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}
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)*)
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