malachite_nz/integer/conversion/string/
from_sci_string.rs

1// Copyright © 2025 Mikhail Hogrefe
2//
3// This file is part of Malachite.
4//
5// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
6// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
7// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
8
9use crate::integer::Integer;
10use crate::natural::conversion::string::from_sci_string::{
11    FromSciStringHelper, from_sci_string_with_options_helper,
12};
13use malachite_base::num::basic::traits::One;
14use malachite_base::num::conversion::string::options::FromSciStringOptions;
15use malachite_base::num::conversion::traits::{FromSciString, FromStringBase};
16
17impl FromSciStringHelper for Integer {
18    fn parse_int(mut cs: &[u8], base: u8) -> Option<Integer> {
19        if let Some(b'+') = cs.first() {
20            cs = &cs[1..];
21            // If the string begins with a '+', the second character cannot be '+' or '-'
22            match cs {
23                [] | [b'+' | b'-', ..] => return None,
24                _ => {}
25            }
26        }
27        Integer::from_string_base(base, core::str::from_utf8(cs).ok()?)
28    }
29
30    fn up_1(self, neg: bool) -> Option<Integer> {
31        Some(if neg {
32            self - Integer::ONE
33        } else {
34            self + Integer::ONE
35        })
36    }
37}
38
39impl FromSciString for Integer {
40    /// Converts a string, possibly in scientfic notation, to an [`Integer`].
41    ///
42    /// Use [`FromSciStringOptions`] to specify the base (from 2 to 36, inclusive) and the rounding
43    /// mode, in case rounding is necessary because the string represents a non-integer.
44    ///
45    /// If the base is greater than 10, the higher digits are represented by the letters `'a'`
46    /// through `'z'` or `'A'` through `'Z'`; the case doesn't matter and doesn't need to be
47    /// consistent.
48    ///
49    /// Exponents are allowed, and are indicated using the character `'e'` or `'E'`. If the base is
50    /// 15 or greater, an ambiguity arises where it may not be clear whether `'e'` is a digit or an
51    /// exponent indicator. To resolve this ambiguity, always use a `'+'` or `'-'` sign after the
52    /// exponent indicator when the base is 15 or greater.
53    ///
54    /// The exponent itself is always parsed using base 10.
55    ///
56    /// Decimal (or other-base) points are allowed. These are most useful in conjunction with
57    /// exponents, but they may be used on their own. If the string represents a non-integer, the
58    /// rounding mode specified in `options` is used to round to an integer.
59    ///
60    /// If the string is unparseable, `None` is returned. `None` is also returned if the rounding
61    /// mode in options is `Exact`, but rounding is necessary.
62    ///
63    /// # Worst-case complexity
64    /// $T(n, m) = O(m^n n \log m (\log n + \log\log m))$
65    ///
66    /// $M(n, m) = O(m^n n \log m)$
67    ///
68    /// where $T$ is time, $M$ is additional memory, $n$ is `s.len()`, and $m$ is `options.base`.
69    ///
70    /// # Examples
71    /// ```
72    /// use malachite_base::num::conversion::string::options::FromSciStringOptions;
73    /// use malachite_base::num::conversion::traits::FromSciString;
74    /// use malachite_base::rounding_modes::RoundingMode::*;
75    /// use malachite_nz::integer::Integer;
76    ///
77    /// assert_eq!(Integer::from_sci_string("123").unwrap(), 123);
78    /// assert_eq!(Integer::from_sci_string("123.5").unwrap(), 124);
79    /// assert_eq!(Integer::from_sci_string("-123.5").unwrap(), -124);
80    /// assert_eq!(Integer::from_sci_string("1.23e10").unwrap(), 12300000000i64);
81    ///
82    /// let mut options = FromSciStringOptions::default();
83    /// assert_eq!(
84    ///     Integer::from_sci_string_with_options("123.5", options).unwrap(),
85    ///     124
86    /// );
87    ///
88    /// options.set_rounding_mode(Floor);
89    /// assert_eq!(
90    ///     Integer::from_sci_string_with_options("123.5", options).unwrap(),
91    ///     123
92    /// );
93    ///
94    /// options = FromSciStringOptions::default();
95    /// options.set_base(16);
96    /// assert_eq!(
97    ///     Integer::from_sci_string_with_options("ff", options).unwrap(),
98    ///     255
99    /// );
100    /// ```
101    #[inline]
102    fn from_sci_string_with_options(s: &str, options: FromSciStringOptions) -> Option<Integer> {
103        from_sci_string_with_options_helper(s, options)
104    }
105}
malachite_nz/integer/conversion/string/from_sci_string.rs

malachite_nz/integer/conversion/string/
from_sci_string.rs
