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Re-implemented ?: parsing in value expressions. "a ? b : c" is implemented by

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translating it into the equivalent syntax tree "(a & b) | c", since this
expression evaluates to the value of b if a is true, otherwise c.
This commit is contained in:
John Wiegley 2008-08-01 01:56:13 -04:00
parent 567902b173
commit c98be73173
3 changed files with 59 additions and 10 deletions
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42
parser.cc
View file

@ -134,7 +134,7 @@ expr_t::parser_t::parse_value_term(std::istream& in,
tok = next_token(in, tflags);
if (tok.kind != token_t::RPAREN)
tok.unexpected(0xff, ')');
tok.expected(')');
node = call_node;
} else {
@ -158,7 +158,7 @@ expr_t::parser_t::parse_value_term(std::istream& in,
tok = next_token(in, tflags);
if (tok.kind != token_t::RPAREN)
tok.unexpected(0xff, ')');
tok.expected(')');
break;
default:
@ -382,11 +382,47 @@ expr_t::parser_t::parse_or_expr(std::istream& in,
return node;
}
expr_t::ptr_op_t
expr_t::parser_t::parse_querycolon_expr(std::istream& in,
const flags_t tflags) const
{
ptr_op_t node(parse_or_expr(in, tflags));
if (node) {
token_t& tok = next_token(in, tflags);
if (tok.kind == token_t::QUERY) {
ptr_op_t prev(node);
node = new op_t(op_t::O_AND);
node->set_left(prev);
node->set_right(parse_or_expr(in, tflags));
if (! node->right())
throw_(parse_error,
tok.symbol << " operator not followed by argument");
token_t& next_tok = next_token(in, tflags);
if (next_tok.kind != token_t::COLON)
next_tok.expected(':');
prev = node;
node = new op_t(op_t::O_OR);
node->set_left(prev);
node->set_right(parse_or_expr(in, tflags));
if (! node->right())
throw_(parse_error,
tok.symbol << " operator not followed by argument");
} else {
push_token(tok);
}
}
return node;
}
expr_t::ptr_op_t
expr_t::parser_t::parse_value_expr(std::istream& in,
const flags_t tflags) const
{
ptr_op_t node(parse_or_expr(in, tflags));
ptr_op_t node(parse_querycolon_expr(in, tflags));
if (node) {
token_t& tok = next_token(in, tflags);

22
token.cc
View file

@ -164,7 +164,7 @@ void expr_t::token_t::next(std::istream& in, const unsigned int pflags)
char buf[256];
READ_INTO_(in, buf, 255, c, length, c != ']');
if (c != ']')
unexpected(c, ']');
expected(']', c);
in.get(c);
length++;
@ -182,7 +182,7 @@ void expr_t::token_t::next(std::istream& in, const unsigned int pflags)
char buf[4096];
READ_INTO_(in, buf, 4095, c, length, c != delim);
if (c != delim)
unexpected(c, delim);
expected(delim, c);
in.get(c);
length++;
kind = VALUE;
@ -196,7 +196,7 @@ void expr_t::token_t::next(std::istream& in, const unsigned int pflags)
temp.parse(in, AMOUNT_PARSE_NO_MIGRATE);
in.get(c);
if (c != '}')
unexpected(c, '}');
expected('}', c);
length++;
kind = VALUE;
value = temp;
@ -231,6 +231,16 @@ void expr_t::token_t::next(std::istream& in, const unsigned int pflags)
kind = STAR;
break;
case '?':
in.get(c);
kind = QUERY;
break;
case ':':
in.get(c);
kind = COLON;
break;
case 'c':
case 'C':
case 'p':
@ -266,7 +276,7 @@ void expr_t::token_t::next(std::istream& in, const unsigned int pflags)
char buf[256];
READ_INTO_(in, buf, 255, c, length, c != '/');
if (c != '/')
unexpected(c, '/');
expected('/', c);
in.get(c);
length++;
@ -379,9 +389,9 @@ void expr_t::token_t::unexpected()
}
}
void expr_t::token_t::unexpected(char c, char wanted)
void expr_t::token_t::expected(char wanted, char c)
{
if (static_cast<unsigned char>(c) == 0xff) {
if (c == '\0') {
if (wanted)
throw_(parse_error, "Missing '" << wanted << "'");
else

5
token.h
View file

@ -71,6 +71,9 @@ struct expr_t::token_t : public noncopyable, public supports_flags<>
KW_OR, // |
KW_MOD, // %
QUERY, // ?
COLON, // :
COMMA, // ,
TOK_EOF,
@ -111,7 +114,7 @@ struct expr_t::token_t : public noncopyable, public supports_flags<>
void rewind(std::istream& in);
void unexpected();
static void unexpected(char c, char wanted = '\0');
static void expected(char wanted, char c = '\0');
};
} // namespace ledger