bkp

orchid-base/src/number.rs

@@ -0,0 +1,150 @@
+use std::num::IntErrorKind;
+use std::ops::Range;
+
+use ordered_float::NotNan;
+use rust_decimal::Decimal;
+
+/// A number, either floating point or unsigned int, parsed by Orchid.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Numeric {
+  /// A nonnegative integer
+  Uint(u64),
+  /// A binary float other than NaN
+  Float(NotNan<f64>),
+  /// A decimal number
+  Decimal(Decimal),
+}
+impl Numeric {
+  pub fn decimal(num: i64, scale: u32) -> Self { Self::Decimal(Decimal::new(num, scale)) }
+  pub fn float(value: f64) -> Self { Self::Float(NotNan::new(value).unwrap()) }
+}
+
+/// Rasons why [parse_num] might fail. See [NumError].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum NumErrorKind {
+  /// The literal describes [f64::NAN]
+  NaN,
+  /// Some integer appearing in the literal overflows [usize]
+  Overflow,
+  /// A character that isn't a digit in the given base was found
+  InvalidDigit,
+}
+impl NumErrorKind {
+  fn from_int(kind: &IntErrorKind) -> Self {
+    match kind {
+      IntErrorKind::InvalidDigit => Self::InvalidDigit,
+      IntErrorKind::NegOverflow | IntErrorKind::PosOverflow => Self::Overflow,
+      _ => panic!("Impossible error condition"),
+    }
+  }
+}
+
+/// Error produced by [parse_num]
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct NumError {
+  /// Location
+  pub range: Range<usize>,
+  /// Reason
+  pub kind: NumErrorKind,
+}
+
+/// Parse a numbre literal out of text
+pub fn parse_num(string: &str) -> Result<Numeric, NumError> {
+  let overflow_err = NumError { range: 0..string.len(), kind: NumErrorKind::Overflow };
+  let (radix, noprefix, pos) = (string.strip_prefix("0x").map(|s| (16u8, s, 2)))
+    .or_else(|| string.strip_prefix("0b").map(|s| (2u8, s, 2)))
+    .or_else(|| string.strip_prefix("0o").map(|s| (8u8, s, 2)))
+    .unwrap_or((10u8, string, 0));
+  // identity
+  let (base, exponent) = match noprefix.split_once('p') {
+    Some((b, e)) => {
+      let (s, d, len) = e.strip_prefix('-').map_or((1, e, 0), |ue| (-1, ue, 1));
+      (b, s * int_parse(d, 10, pos + b.len() + 1 + len)? as i32)
+    },
+    None => (noprefix, 0),
+  };
+  match base.split_once('.') {
+    None => {
+      let base_usize = int_parse(base, radix, pos)?;
+      if let Ok(pos_exp) = u32::try_from(exponent) {
+        if let Some(radical) = u64::from(radix).checked_pow(pos_exp) {
+          let number = base_usize.checked_mul(radical).ok_or(overflow_err)?;
+          return Ok(Numeric::Uint(number));
+        }
+      }
+      let f = (base_usize as f64) * (radix as f64).powi(exponent);
+      let err = NumError { range: 0..string.len(), kind: NumErrorKind::NaN };
+      Ok(Numeric::Float(NotNan::new(f).map_err(|_| err)?))
+    },
+    Some((whole, part)) => {
+      let whole_n = int_parse(whole, radix, pos)?;
+      let part_n = int_parse(part, radix, pos + whole.len() + 1)?;
+      let scale = part.chars().filter(|c| *c != '_').count() as u32;
+      if radix == 10 {
+        let mut scaled_unit = Decimal::ONE;
+        (scaled_unit.set_scale(scale))
+          .map_err(|_| NumError { range: 0..string.len(), kind: NumErrorKind::Overflow })?;
+        Ok(Numeric::Decimal(Decimal::from(whole_n) + scaled_unit * Decimal::from(part_n)))
+      } else {
+        let real_val = whole_n as f64 + (part_n as f64 / (radix as f64).powi(scale as i32));
+        let f = real_val * (radix as f64).powi(exponent);
+        Ok(Numeric::Float(NotNan::new(f).expect("None of the inputs are NaN")))
+      }
+    },
+  }
+}
+
+fn int_parse(s: &str, radix: u8, start: usize) -> Result<u64, NumError> {
+  let s = s.chars().filter(|c| *c != '_').collect::<String>();
+  let range = start..(start + s.len());
+  u64::from_str_radix(&s, radix as u32)
+    .map_err(|e| NumError { range, kind: NumErrorKind::from_int(e.kind()) })
+}
+
+/// Filter for characters that can appear in numbers
+pub fn numchar(c: char) -> bool { c.is_alphanumeric() | "._-".contains(c) }
+/// Filter for characters that can start numbers
+pub fn numstart(c: char) -> bool { c.is_ascii_digit() }
+
+/// Print a number as a base-16 floating point literal
+#[must_use]
+pub fn print_nat16(num: NotNan<f64>) -> String {
+  if *num == 0.0 {
+    return "0x0".to_string();
+  } else if num.is_infinite() {
+    return match num.is_sign_positive() {
+      true => "Infinity".to_string(),
+      false => "-Infinity".to_string(),
+    };
+  } else if num.is_nan() {
+    return "NaN".to_string();
+  }
+  let exp = num.log(16.0).floor();
+  let man = *num / 16_f64.powf(exp);
+  format!("0x{man}p{exp:.0}")
+}
+
+#[cfg(test)]
+mod test {
+  use super::{parse_num, Numeric};
+
+  #[test]
+  fn just_ints() {
+    let test = |s, n| assert_eq!(parse_num(s), Ok(Numeric::Uint(n)));
+    test("12345", 12345);
+    test("0xcafebabe", 0xcafebabe);
+    test("0o751", 0o751);
+    test("0b111000111", 0b111000111);
+  }
+
+  #[test]
+  fn decimals() {
+    let test = |s, n| assert_eq!(parse_num(s), Ok(n));
+    test("3.1417", Numeric::decimal(31417, 4));
+    test("0xf.cafe", Numeric::float(0xf as f64 + 0xcafe as f64 / 0x10000 as f64));
+    test("34p3", Numeric::Uint(34000));
+    test("0x2p3", Numeric::Uint(0x2 * 0x1000));
+    test("1.5p3", Numeric::decimal(1500, 0));
+    test("0x2.5p3", Numeric::float((0x25 * 0x100) as f64));
+  }
+}