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diff --git a/third_party/python/ply/README.md b/third_party/python/ply/README.md new file mode 100644 index 0000000000..e428f1b14a --- /dev/null +++ b/third_party/python/ply/README.md @@ -0,0 +1,273 @@ +PLY (Python Lex-Yacc) Version 3.10 + +Copyright (C) 2001-2017 +David M. Beazley (Dabeaz LLC) +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are +met: + +* Redistributions of source code must retain the above copyright notice, + this list of conditions and the following disclaimer. +* Redistributions in binary form must reproduce the above copyright notice, + this list of conditions and the following disclaimer in the documentation + and/or other materials provided with the distribution. +* Neither the name of the David Beazley or Dabeaz LLC may be used to + endorse or promote products derived from this software without + specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +Introduction +============ + +PLY is a 100% Python implementation of the common parsing tools lex +and yacc. Here are a few highlights: + + - PLY is very closely modeled after traditional lex/yacc. + If you know how to use these tools in C, you will find PLY + to be similar. + + - PLY provides *very* extensive error reporting and diagnostic + information to assist in parser construction. The original + implementation was developed for instructional purposes. As + a result, the system tries to identify the most common types + of errors made by novice users. + + - PLY provides full support for empty productions, error recovery, + precedence specifiers, and moderately ambiguous grammars. + + - Parsing is based on LR-parsing which is fast, memory efficient, + better suited to large grammars, and which has a number of nice + properties when dealing with syntax errors and other parsing problems. + Currently, PLY builds its parsing tables using the LALR(1) + algorithm used in yacc. + + - PLY uses Python introspection features to build lexers and parsers. + This greatly simplifies the task of parser construction since it reduces + the number of files and eliminates the need to run a separate lex/yacc + tool before running your program. + + - PLY can be used to build parsers for "real" programming languages. + Although it is not ultra-fast due to its Python implementation, + PLY can be used to parse grammars consisting of several hundred + rules (as might be found for a language like C). The lexer and LR + parser are also reasonably efficient when parsing typically + sized programs. People have used PLY to build parsers for + C, C++, ADA, and other real programming languages. + +How to Use +========== + +PLY consists of two files : lex.py and yacc.py. These are contained +within the 'ply' directory which may also be used as a Python package. +To use PLY, simply copy the 'ply' directory to your project and import +lex and yacc from the associated 'ply' package. For example: + + import ply.lex as lex + import ply.yacc as yacc + +Alternatively, you can copy just the files lex.py and yacc.py +individually and use them as modules. For example: + + import lex + import yacc + +The file setup.py can be used to install ply using distutils. + +The file doc/ply.html contains complete documentation on how to use +the system. + +The example directory contains several different examples including a +PLY specification for ANSI C as given in K&R 2nd Ed. + +A simple example is found at the end of this document + +Requirements +============ +PLY requires the use of Python 2.6 or greater. However, you should +use the latest Python release if possible. It should work on just +about any platform. PLY has been tested with both CPython and Jython. +It also seems to work with IronPython. + +Resources +========= +More information about PLY can be obtained on the PLY webpage at: + + http://www.dabeaz.com/ply + +For a detailed overview of parsing theory, consult the excellent +book "Compilers : Principles, Techniques, and Tools" by Aho, Sethi, and +Ullman. The topics found in "Lex & Yacc" by Levine, Mason, and Brown +may also be useful. + +The GitHub page for PLY can be found at: + + https://github.com/dabeaz/ply + +An old and relatively inactive discussion group for PLY is found at: + + http://groups.google.com/group/ply-hack + +Acknowledgments +=============== +A special thanks is in order for all of the students in CS326 who +suffered through about 25 different versions of these tools :-). + +The CHANGES file acknowledges those who have contributed patches. + +Elias Ioup did the first implementation of LALR(1) parsing in PLY-1.x. +Andrew Waters and Markus Schoepflin were instrumental in reporting bugs +and testing a revised LALR(1) implementation for PLY-2.0. + +Special Note for PLY-3.0 +======================== +PLY-3.0 the first PLY release to support Python 3. However, backwards +compatibility with Python 2.6 is still preserved. PLY provides dual +Python 2/3 compatibility by restricting its implementation to a common +subset of basic language features. You should not convert PLY using +2to3--it is not necessary and may in fact break the implementation. + +Example +======= + +Here is a simple example showing a PLY implementation of a calculator +with variables. + + # ----------------------------------------------------------------------------- + # calc.py + # + # A simple calculator with variables. + # ----------------------------------------------------------------------------- + + tokens = ( + 'NAME','NUMBER', + 'PLUS','MINUS','TIMES','DIVIDE','EQUALS', + 'LPAREN','RPAREN', + ) + + # Tokens + + t_PLUS = r'\+' + t_MINUS = r'-' + t_TIMES = r'\*' + t_DIVIDE = r'/' + t_EQUALS = r'=' + t_LPAREN = r'\(' + t_RPAREN = r'\)' + t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*' + + def t_NUMBER(t): + r'\d+' + t.value = int(t.value) + return t + + # Ignored characters + t_ignore = " \t" + + def t_newline(t): + r'\n+' + t.lexer.lineno += t.value.count("\n") + + def t_error(t): + print("Illegal character '%s'" % t.value[0]) + t.lexer.skip(1) + + # Build the lexer + import ply.lex as lex + lex.lex() + + # Precedence rules for the arithmetic operators + precedence = ( + ('left','PLUS','MINUS'), + ('left','TIMES','DIVIDE'), + ('right','UMINUS'), + ) + + # dictionary of names (for storing variables) + names = { } + + def p_statement_assign(p): + 'statement : NAME EQUALS expression' + names[p[1]] = p[3] + + def p_statement_expr(p): + 'statement : expression' + print(p[1]) + + def p_expression_binop(p): + '''expression : expression PLUS expression + | expression MINUS expression + | expression TIMES expression + | expression DIVIDE expression''' + if p[2] == '+' : p[0] = p[1] + p[3] + elif p[2] == '-': p[0] = p[1] - p[3] + elif p[2] == '*': p[0] = p[1] * p[3] + elif p[2] == '/': p[0] = p[1] / p[3] + + def p_expression_uminus(p): + 'expression : MINUS expression %prec UMINUS' + p[0] = -p[2] + + def p_expression_group(p): + 'expression : LPAREN expression RPAREN' + p[0] = p[2] + + def p_expression_number(p): + 'expression : NUMBER' + p[0] = p[1] + + def p_expression_name(p): + 'expression : NAME' + try: + p[0] = names[p[1]] + except LookupError: + print("Undefined name '%s'" % p[1]) + p[0] = 0 + + def p_error(p): + print("Syntax error at '%s'" % p.value) + + import ply.yacc as yacc + yacc.yacc() + + while True: + try: + s = raw_input('calc > ') # use input() on Python 3 + except EOFError: + break + yacc.parse(s) + + +Bug Reports and Patches +======================= +My goal with PLY is to simply have a decent lex/yacc implementation +for Python. As a general rule, I don't spend huge amounts of time +working on it unless I receive very specific bug reports and/or +patches to fix problems. I also try to incorporate submitted feature +requests and enhancements into each new version. Please visit the PLY +github page at https://github.com/dabeaz/ply to submit issues and pull +requests. To contact me about bugs and/or new features, please send +email to dave@dabeaz.com. + +-- Dave + + + + + + + + + |