src/test/auxiliary/roman_numerals.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // force-host
  12
  13 #![crate_type="dylib"]
  14 #![feature(plugin_registrar, rustc_private)]
  15 #![feature(slice_patterns)]
  16
  17 extern crate syntax;
  18 extern crate rustc;
  19 extern crate rustc_plugin;
  20
  21 use syntax::codemap::Span;
  22 use syntax::ast::TokenTree;
  23 use syntax::parse::token;
  24 use syntax::ext::base::{ExtCtxt, MacResult, DummyResult, MacEager};
  25 use syntax::ext::build::AstBuilder;  // trait for expr_usize
  26 use rustc_plugin::Registry;
  27
  28 // WARNING WARNING WARNING WARNING WARNING
  29 // =======================================
  30 //
  31 // This code also appears in src/doc/guide-plugin.md. Please keep
  32 // the two copies in sync!  FIXME: have rustdoc read this file
  33
  34 fn expand_rn(cx: &mut ExtCtxt, sp: Span, args: &[TokenTree])
  35         -> Box<MacResult + 'static> {
  36
  37     static NUMERALS: &'static [(&'static str, usize)] = &[
  38         ("M", 1000), ("CM", 900), ("D", 500), ("CD", 400),
  39         ("C",  100), ("XC",  90), ("L",  50), ("XL",  40),
  40         ("X",   10), ("IX",   9), ("V",   5), ("IV",   4),
  41         ("I",    1)];
  42
  43     if args.len() != 1 {
  44         cx.span_err(
  45             sp,
  46             &format!("argument should be a single identifier, but got {} arguments", args.len()));
  47         return DummyResult::any(sp);
  48     }
  49
  50     let text = match args[0] {
  51         TokenTree::Token(_, token::Ident(s, _)) => s.to_string(),
  52         _ => {
  53             cx.span_err(sp, "argument should be a single identifier");
  54             return DummyResult::any(sp);
  55         }
  56     };
  57
  58     let mut text = &*text;
  59     let mut total = 0;
  60     while !text.is_empty() {
  61         match NUMERALS.iter().find(|&&(rn, _)| text.starts_with(rn)) {
  62             Some(&(rn, val)) => {
  63                 total += val;
  64                 text = &text[rn.len()..];
  65             }
  66             None => {
  67                 cx.span_err(sp, "invalid Roman numeral");
  68                 return DummyResult::any(sp);
  69             }
  70         }
  71     }
  72
  73     MacEager::expr(cx.expr_usize(sp, total))
  74 }
  75
  76 #[plugin_registrar]
  77 pub fn plugin_registrar(reg: &mut Registry) {
  78     reg.register_macro("rn", expand_rn);
  79 }