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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![doc(hidden)]
macro_rules! assert_approx_eq {
($a:expr, $b:expr) => ({
use num::Float;
let (a, b) = (&$a, &$b);
assert!((*a - *b).abs() < 1.0e-6,
"{} is not approximately equal to {}", *a, *b);
})
}
macro_rules! from_str_radix_float_impl {
($T:ty) => {
fn from_str_radix(src: &str, radix: u32)
-> Result<$T, ParseFloatError> {
use num::FloatErrorKind::*;
use num::ParseFloatError as PFE;
// Special values
match src {
"inf" => return Ok(Float::infinity()),
"-inf" => return Ok(Float::neg_infinity()),
"NaN" => return Ok(Float::nan()),
_ => {},
}
let (is_positive, src) = match src.slice_shift_char() {
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 src.slice_shift_char() {
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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