parser: Script for extended sablecc3 syntax

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

diff --git a/src/parser/prescc.sh b/src/parser/prescc.sh
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+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Copyright 2009 Jean Privat <jean@pryen.org>
+#
+# 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 with shell, sed and 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
+#                ;
+
+
+case $# in
+       2);;
+       *) echo "Usage: prescc infile outfile"; exit
+esac
+
+
+infile=$1
+outfile=$2
+tmpfile=`mktemp "$2.XXXXXX"`
+
+echo -n "/* This file is autogenerated, do not modify it */" > "$outfile"
+cat "$infile" >> "$outfile"
+
+# The perl code is used to list all the available parameters in the extended grammar
+for token in `perl -ne 'if (/\~(\w+)/ && !$found{$1}) {print "$1\n"; $found{$1}=1}' "$infile"`
+do
+       echo "Parameter ~$token"
+       # first, sed starts from first line to the AST line and removes ~xxx and !xxx
+       sed -n -e "1,/^Abstract Syntax Tree/{/^Abstract Syntax Tree/b;s/[\~!]$token//g;p}" "$outfile" > "$tmpfile"
+       # second, sed clones ~xxx parametrized productions, substitute ~xxx with _xxx and delete !xxx lines
+       sed -n -e "/\~$token/,/;/{s/\~$token/_$token/g;/!$token/d;p}" "$outfile" >> "$tmpfile"
+       # third, sed continues fron AST line to last line and remove ~xxx and !xxx
+       sed -n -e "/^Abstract Syntax Tree/,\${s/[\~!]$token//g;p}" "$outfile" >> "$tmpfile"
+       mv "$tmpfile" "$outfile"
+done
+