scientific_macro/
lib.rs

1//! Macro for [scientific](https://docs.rs/scientific/latest/scientific/), the arbitrary precision scientific number. Not intended to be used directly.
2
3use crate::parser::parse_scientific;
4use proc_macro::TokenStream;
5use proc_macro2::{Delimiter, Group, Punct, Spacing, Span, TokenStream as TokenStream2};
6use quote::{quote, ToTokens, TokenStreamExt};
7use syn::parse::{Parse, ParseStream};
8use syn::{parse_macro_input, Error, LitFloat, LitInt, Token};
9
10mod parser;
11
12// Helper: allow parsing Int or Float
13enum LitIntOrLitFloat {
14  LitInt(LitInt),
15  LitFloat(LitFloat),
16}
17
18impl LitIntOrLitFloat {
19  fn base10_digits(&self) -> &str {
20    match self {
21      LitIntOrLitFloat::LitInt(num) => num.base10_digits(),
22      LitIntOrLitFloat::LitFloat(num) => num.base10_digits(),
23    }
24  }
25
26  fn suffix(&self) -> &str {
27    match self {
28      LitIntOrLitFloat::LitInt(num) => num.suffix(),
29      LitIntOrLitFloat::LitFloat(num) => num.suffix(),
30    }
31  }
32
33  fn span(&self) -> Span {
34    match self {
35      LitIntOrLitFloat::LitInt(num) => num.span(),
36      LitIntOrLitFloat::LitFloat(num) => num.span(),
37    }
38  }
39}
40
41impl Parse for LitIntOrLitFloat {
42  fn parse(input: ParseStream) -> Result<Self, Error> {
43    let lookahead = input.lookahead1();
44    if lookahead.peek(LitInt) {
45      input.parse().map(LitIntOrLitFloat::LitInt)
46    } else if lookahead.peek(LitFloat) {
47      input.parse().map(LitIntOrLitFloat::LitFloat)
48    } else {
49      Err(lookahead.error())
50    }
51  }
52}
53
54// Helper: Parse LitScientific (optional minus sign and LitIntOrLitFloat)
55struct LitScientific {
56  neg: Option<Token![-]>,
57  num: LitIntOrLitFloat,
58}
59
60impl Parse for LitScientific {
61  fn parse(input: ParseStream) -> Result<Self, Error> {
62    Ok(LitScientific {
63      neg: input.parse()?,
64      num: input.parse()?,
65    })
66  }
67}
68
69// Helper: Convert to Tokens as a slice
70struct AsSlice<'a>(&'a [u8]);
71
72impl<'a> ToTokens for AsSlice<'a> {
73  fn to_tokens(&self, stream: &mut TokenStream2) {
74    let mut body_stream = TokenStream2::new();
75    for d in self.0.iter() {
76      d.to_tokens(&mut body_stream);
77      body_stream.append(Punct::new(',', Spacing::Alone));
78    }
79    stream.append(Group::new(Delimiter::Bracket, body_stream));
80  }
81}
82
83// Actual macro
84/// Macro for Scientific (Arbitrary precision scientific number)
85///
86/// Create a constant `Scientific` number.
87#[allow(non_snake_case)]
88#[proc_macro]
89pub fn Scientific(item: TokenStream) -> TokenStream {
90  let LitScientific { neg, num } = parse_macro_input!(item as LitScientific);
91  if !num.suffix().is_empty() {
92    return TokenStream::from(Error::new(num.span(), "No suffix allowed").to_compile_error());
93  }
94  match parse_scientific(num.base10_digits()) {
95    Err(()) => TokenStream::from(Error::new(num.span(), "Parse error").to_compile_error()),
96    Ok(None) => quote!(::scientific::Scientific::ZERO).into(),
97    Ok(Some((mantissa, exponent))) => {
98      let neg = neg.is_some();
99      let len = mantissa.len();
100      let mantissa = AsSlice(&mantissa);
101      quote!(
102        {
103          const MANTISSA: [u8; #len] = #mantissa;
104          ::scientific::Scientific::unchecked_non_zero_static_new(#neg, &MANTISSA, #exponent)
105        }
106      )
107      .into()
108    }
109  }
110}
scientific_macro/lib.rs

scientific_macro/
lib.rs
