malachite_nz/integer/conversion/string/
from_sci_string.rs

1// Copyright © 2026 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<Self> {
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        Self::from_string_base(base, core::str::from_utf8(cs).ok()?)
28    }
29
30    fn up_1(self, neg: bool) -> Option<Self> {
31        Some(if neg {
32            self - Self::ONE
33        } else {
34            self + Self::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    /// $T(n, m) = O(B (\log B)^2 \log\log B)$
65    ///
66    /// $M(n, m) = O(B \log B)$
67    ///
68    /// where $T$ is time, $M$ is additional memory, $n$ is `s.len()`, $m$ is `options.base`, and
69    /// $B$ is $10^n \log m$, a bound on the bit length of the result: the exponent is parsed in
70    /// base 10, so a string of length $n$ can denote a number of up to about $10^n \log_2 m$ bits,
71    /// and building it costs one power and one multiplication at that size.
72    ///
73    /// # Examples
74    /// ```
75    /// use malachite_base::num::conversion::string::options::FromSciStringOptions;
76    /// use malachite_base::num::conversion::traits::FromSciString;
77    /// use malachite_base::rounding_modes::RoundingMode::*;
78    /// use malachite_nz::integer::Integer;
79    ///
80    /// assert_eq!(Integer::from_sci_string("123").unwrap(), 123);
81    /// assert_eq!(Integer::from_sci_string("123.5").unwrap(), 124);
82    /// assert_eq!(Integer::from_sci_string("-123.5").unwrap(), -124);
83    /// assert_eq!(Integer::from_sci_string("1.23e10").unwrap(), 12300000000i64);
84    ///
85    /// let mut options = FromSciStringOptions::default();
86    /// assert_eq!(
87    ///     Integer::from_sci_string_with_options("123.5", options).unwrap(),
88    ///     124
89    /// );
90    ///
91    /// options.set_rounding_mode(Floor);
92    /// assert_eq!(
93    ///     Integer::from_sci_string_with_options("123.5", options).unwrap(),
94    ///     123
95    /// );
96    ///
97    /// options = FromSciStringOptions::default();
98    /// options.set_base(16);
99    /// assert_eq!(
100    ///     Integer::from_sci_string_with_options("ff", options).unwrap(),
101    ///     255
102    /// );
103    /// ```
104    #[inline]
105    fn from_sci_string_with_options(s: &str, options: FromSciStringOptions) -> Option<Self> {
106        from_sci_string_with_options_helper(s, options)
107    }
108}
malachite_nz/integer/conversion/string/from_sci_string.rs

malachite_nz/integer/conversion/string/
from_sci_string.rs
