handle read errors better (02ea4b5f) · Commits · lisp / lis.pl

Interp.pm

+10 −2

Original line number	Diff line number	Diff line
		@@ -61,8 +61,16 @@ sub repl {
		if ($interactive) {
		print("> ");
		}
		my $expr = eval {
		my $expr = Read($fh);
		last unless defined($expr);
		return $expr;
		};
		if ($@) {
		say("Error: $@");
		next;
		} elsif (!defined($expr)) {
		last;
		}

		if ($interactive) {
		$value = iEval($expr);

Read.pm

+28 −14

Original line number	Diff line number	Diff line
		@@ -25,13 +25,21 @@ my $default_input = \*STDIN;

		my $sepchars = quotemeta("();\n");

		# after a read error, consume to end of line
		sub read_error {
		my ($in, @rest) = @_;
		<$in>;
		error(@rest);
		}

		sub Read {
		my ($in) = @_;
		$in //= $default_input;
		if (stringp($in)) {
		my $string = $in;
		open(my $str_in, "<", \$string) or
		error("read: cannot open string as filehandle: $!\n");
		read_error($in,
		"read: cannot open string as filehandle: $!\n");
		$in = $str_in;
		}

		@@ -42,25 +50,28 @@ sub Read {
		my $list = read_list_elems($in);
		return undef unless defined($list);
		my $closer = next_token($in);
		return error("syntax: list closed by $closer: ", $in)
		return read_error($in, "syntax: list closed by $closer: ", $in)
		unless $closer eq ')';
		return $list;
		} elsif ($t eq '\'') {
		$t = Read($in);
		return error("EOF in quote: %s", $in) unless defined($t);
		return read_error($in, "EOF in quote: %s", $in)
		unless defined($t);
		return list(intern($Quote), $t);
		} elsif ($t eq '#\'') {
		$t = Read($in);
		return error("EOF in quote %s", $in) unless defined($t);
		return read_error($in, "EOF in quote %s", $in)
		unless defined($t);
		return list(intern($n_function), $t);
		} elsif ($t eq '.') {
		return error("found . where sexpr was expected: %s", $in);
		return read_error($in,
		"found . where sexpr was expected: %s", $in);
		} elsif (symbolp($t)) {
		return $t;
		} elsif ($t =~ m{^\"}) {
		return substr($t, 1);
		} elsif ($t eq ')') {
		return error("close paren unexpected");
		return read_error($in, "close paren unexpected");
		} else {
		return $t;
		}
		@@ -77,13 +88,15 @@ sub read_list_elems {
		push_back_token($t);
		return $list;
		} elsif ($t eq '.') {
		return error("syntax: . at start of list: %s",
		return read_error($in, "syntax: . at start of list: %s",
		$in)
		unless $end;
		my $sexpr = Read($in);
		return undef unless defined($t);
		$t = next_token($in);
		return error("syntax: no ) after improper list: %s",
		return
		read_error($in,
		"syntax: no ) after improper list: %s",
		$in)
		unless $t eq ')';
		rplacd($end, $sexpr);
		@@ -101,7 +114,7 @@ sub read_list_elems {
		}
		}
		}
		return error("EOF while reading list elements: %s", $in);
		return read_error($in, "EOF while reading list elements: %s", $in);
		}


		@@ -181,23 +194,24 @@ sub symbol_or_number_or_dot {
		sub error_or_eof {
		my ($in) = @_;
		if (defined($!)) {
		return error("read failure line $.: $!: %s", $in);
		return read_error($in, "read failure line $.: $!: %s", $in);
		}
		return error("unexpected EOF line $.: %s", $in);
		return read_error($in, "unexpected EOF line $.: %s", $in);
		}

		sub read_macro {
		my ($in) = @_;
		#debug("read macro");
		my $c = next_nonwhite($in);
		return error("unexpected EOF line $.: %s", $in) unless defined($c);
		return read_error($in, "unexpected EOF line $.: %s", $in)
		unless defined($c);
		if ($c eq '\'') {
		my $result = '#\'';
		#debug("read macro returns %s", $result);
		return $result;
		# and possibly more
		} else {
		return error("unknown reader macro \"#$c\": %s", $in);
		return read_error($in, "unknown reader macro \"#$c\": %s", $in);
		}
		}