parser: migrate prescc to Perl

[nit.git] / src / parser / prescc.pl

diff --git a/src/parser/prescc.pl b/src/parser/prescc.pl
new file mode 100755 (executable)
index 0000000..4159cf8
--- /dev/null
+++ b/src/parser/prescc.pl
@@ -0,0 +1,104 @@
+#!/usr/bin/perl -w
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Copyright 2009 Jean Privat <jean@pryen.org>
+# Copyright 2009 Jean-Sebastien Gelinas <calestar@gmail.com>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# prescc, a Sablecc preprocessor.
+#
+# Synopsis
+#
+#   Extends a sablecc grammar with parametrized productions.
+#
+# Description
+#
+#   A production named foo~bar~baz semantically correspond to a production foo with two boolean parameters bar and baz
+#   In fact foo is a family of 4 distinct productions: foo, foo_bar, foo_baz and foo_bar_baz
+#   In a parametrized production with a parameter ~xxx:
+#    * parameters (~xxx) are substituted with _xxx if the parameter is true and removed if the parameter is false
+#    * guarded alternatives (!xxx) are disabled if the parameter is true
+#
+# Limitations
+#
+#   prescc is badly implemented in perl and is not robust.
+#   Users must remember the following:
+#    * parametrized productions MUST be terminated with a line containing only a single semicolon (;)
+#    * parameters (~) and guards (!) in alternatives MUST correspond to a parameter of the enclosing production
+#    * if required, names in transformations MUST contain the full invocation name (with all parameters)
+#        foo bar_x~y~z_t baz {-> New p(foo, bar_x~y~z_t.q)}
+#    * guards do not understand grammar, they just remove the whole line
+#    * The AST MUST start with a line containing only "Abstract Syntax Tree"
+#
+# Example of the dangling else implementation:
+#
+#   stmt~withelse =
+#                'if' expr 'then' stmt_withelse 'else' stmt~withelse |
+#     !withelse  'if' expr 'then' stmt |
+#                nop
+#                ;
+
+while (<>) {
+       push @lines, $_;
+}
+$lines = join "", @lines;
+
+# List all the available parameters in the extended grammar
+@params = ();
+while ($lines =~ /\~([a-zA-Z]+)/g) {
+       if (!$found{$1}) {
+               push @params, $1;
+               $found{$1}=1;
+       }
+}
+
+$ast = "Abstract Syntax Tree";
+@res = ();
+for $token (@params) {
+       print STDERR "Parameter ~$token\n";
+       #push @res, "//Start part $token\n";
+# first, sed starts from first line to the AST line and removes ~xxx and !xxx
+       for $l (@lines) {
+               $_ = $l;
+               last if (/^$ast/);
+               s/[~!]$token//g;
+               push @res, $_;
+       }
+       #push @res, "//Generated part $token\n";
+       # second, sed clones ~xxx parametrized productions, substitute ~xxx with _xxx and delete !xxx lines
+       $into = 0;
+       for $l (@lines) {
+               $_ = $l;
+               $into = 1 if (/~$token/);
+               next if (!$into);
+               s/~$token/_$token/g;
+               next if /!$token/;
+               push @res, $_;
+               $into = 0 if (/;/);
+       }
+       #push @res, "//End of generated part $token\n";
+
+       # third, sed continues fron AST line to last line and remove ~xxx and !xxx
+       $into = 0;
+       for (@lines) {
+               $into = 1 if (/^$ast/);
+               next if (!$into);
+               push @res, $_;
+       }
+       #push @res, "//End part $token\n";
+       @lines = @res;
+       @res = ();
+}
+print "/* This file is autogenerated, do not modify it */";
+print (join "", @lines);