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
  20 use syntax::codemap::Span;
  21 use syntax::parse::token;
  22 use syntax::ast::{TokenTree, TtToken};
  23 use syntax::ext::base::{ExtCtxt, MacResult, DummyResult, MacEager};
  24 use syntax::ext::build::AstBuilder;  // trait for expr_usize
  25 use rustc::plugin::Registry;
  26
  27 // WARNING WARNING WARNING WARNING WARNING
  28 // =======================================
  29 //
  30 // This code also appears in src/doc/guide-plugin.md. Please keep
  31 // the two copies in sync!  FIXME: have rustdoc read this file
  32
  33 fn expand_rn(cx: &mut ExtCtxt, sp: Span, args: &[TokenTree])
  34         -> Box<MacResult + 'static> {
  35
  36     static NUMERALS: &'static [(&'static str, usize)] = &[
  37         ("M", 1000), ("CM", 900), ("D", 500), ("CD", 400),
  38         ("C",  100), ("XC",  90), ("L",  50), ("XL",  40),
  39         ("X",   10), ("IX",   9), ("V",   5), ("IV",   4),
  40         ("I",    1)];
  41
  42     let text = match args {
  43         [TtToken(_, token::Ident(s, _))] => token::get_ident(s).to_string(),
  44         _ => {
  45             cx.span_err(sp, "argument should be a single identifier");
  46             return DummyResult::any(sp);
  47         }
  48     };
  49
  50     let mut text = &*text;
  51     let mut total = 0;
  52     while !text.is_empty() {
  53         match NUMERALS.iter().find(|&&(rn, _)| text.starts_with(rn)) {
  54             Some(&(rn, val)) => {
  55                 total += val;
  56                 text = &text[rn.len()..];
  57             }
  58             None => {
  59                 cx.span_err(sp, "invalid Roman numeral");
  60                 return DummyResult::any(sp);
  61             }
  62         }
  63     }
  64
  65     MacEager::expr(cx.expr_usize(sp, total))
  66 }
  67
  68 #[plugin_registrar]
  69 pub fn plugin_registrar(reg: &mut Registry) {
  70     reg.register_macro("rn", expand_rn);
  71 }