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Support an alternate for syntax that calls a higher-order function

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The last argument of the call must be a block, and the type of this
argument must a function returning bool. `break` and `cont` are
supported in the body of the block, and return `false` or `true` from
the function. When the end of the function is reached, `true` is
implicitly returned.

    for vec::all([1, 2, 3]) {|elt|
        if elt == 2 { break; }
        log(error, elt);
    }

Issue #1619
This commit is contained in:
Marijn Haverbeke 2012-03-26 16:09:27 +02:00
parent 9638e7fece
commit f6e3738b9c
15 changed files with 123 additions and 78 deletions
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38
src/rustc/syntax/parse/parser.rs
View file

@ -1403,13 +1403,37 @@ fn parse_else_expr(p: parser) -> @ast::expr {
}
fn parse_for_expr(p: parser) -> @ast::expr {
let lo = p.last_span.lo;
let decl = parse_local(p, false, false);
expect_word(p, "in");
let seq = parse_expr(p);
let body = parse_block_no_value(p);
let mut hi = body.span.hi;
ret mk_expr(p, lo, hi, ast::expr_for(decl, seq, body));
let lo = p.last_span;
// FIXME remove this kludge after migration and snapshotting (#1619)
let new_style = alt p.token {
token::IDENT(_, false) { alt p.look_ahead(1u) {
token::DOT | token::LPAREN { true }
_ { false }
} }
token::IDENT(_, true) { true }
_ { false }
};
if new_style {
let call = parse_expr(p);
alt call.node {
ast::expr_call(f, args, true) {
let b_arg = vec::last(args);
let last = mk_expr(p, b_arg.span.lo, b_arg.span.hi,
ast::expr_loop_body(b_arg));
@{node: ast::expr_call(f, vec::init(args) + [last], true)
with *call}
}
_ {
p.span_fatal(lo, "`for` must be followed by a block call");
}
}
} else {
let decl = parse_local(p, false, false);
expect_word(p, "in");
let seq = parse_expr(p);
let body = parse_block_no_value(p);
mk_expr(p, lo.lo, body.span.hi, ast::expr_for(decl, seq, body))
}
}
fn parse_while_expr(p: parser) -> @ast::expr {