bjoernager/rust
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Refactor operator precedence code

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Use functions instead of a dynamically created table to determine
operator precedence. Gets rid of a FIXME in syntax::parse::prec.
Change precedences from int to uint while we're at it, since
don't use negative precedences.
This commit is contained in:
Tim Chevalier 2012-04-26 16:13:59 -07:00
parent 1f92538e38
commit 8e15640ada
6 changed files with 74 additions and 55 deletions
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34
src/librustsyntax/parse/parser.rs
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@ -4,10 +4,10 @@ import std::map::{hashmap, str_hash};
import token::{can_begin_expr, is_ident, is_plain_ident};
import codemap::{span,fss_none};
import util::interner;
import ast_util::{spanned, mk_sp, ident_to_path};
import ast_util::{spanned, mk_sp, ident_to_path, operator_prec};
import ast::{node_id};
import lexer::reader;
import prec::{op_spec, as_prec};
import prec::{as_prec, token_to_binop};
import attr::{parse_outer_attrs_or_ext,
parse_inner_attrs_and_next,
parse_outer_attributes,
@ -57,7 +57,6 @@ type parser = @{
mut buffer: [{tok: token::token, span: span}],
mut restriction: restriction,
reader: reader,
binop_precs: @[op_spec],
keywords: hashmap<str, ()>,
restricted_keywords: hashmap<str, ()>
};
@ -1040,26 +1039,31 @@ fn parse_prefix_expr(p: parser) -> pexpr {
fn parse_binops(p: parser) -> @ast::expr {
ret parse_more_binops(p, parse_prefix_expr(p), 0);
ret parse_more_binops(p, parse_prefix_expr(p), 0u);
}
fn parse_more_binops(p: parser, plhs: pexpr, min_prec: int) ->
fn parse_more_binops(p: parser, plhs: pexpr, min_prec: uint) ->
@ast::expr {
let lhs = to_expr(plhs);
if expr_is_complete(p, plhs) { ret lhs; }
let peeked = p.token;
if peeked == token::BINOP(token::OR) &&
p.restriction == RESTRICT_NO_BAR_OP { ret lhs; }
for vec::each(*p.binop_precs) {|cur|
if cur.prec > min_prec && cur.tok == peeked {
p.bump();
let expr = parse_prefix_expr(p);
let rhs = parse_more_binops(p, expr, cur.prec);
p.get_id(); // see ast_util::op_expr_callee_id
let bin = mk_pexpr(p, lhs.span.lo, rhs.span.hi,
ast::expr_binary(cur.op, lhs, rhs));
ret parse_more_binops(p, bin, min_prec);
}
let cur_opt = token_to_binop(peeked);
alt cur_opt {
some(cur_op) {
let cur_prec = operator_prec(cur_op);
if cur_prec > min_prec {
p.bump();
let expr = parse_prefix_expr(p);
let rhs = parse_more_binops(p, expr, cur_prec);
p.get_id(); // see ast_util::op_expr_callee_id
let bin = mk_pexpr(p, lhs.span.lo, rhs.span.hi,
ast::expr_binary(cur_op, lhs, rhs));
ret parse_more_binops(p, bin, min_prec);
}
}
_ {}
}
if as_prec > min_prec && eat_keyword(p, "as") {
let rhs = parse_ty(p, true);