Massive refactoring/cleanup

CHANGES

@@ -4,10 +4,42 @@ IMPORTANT NOTE (2018-12-22): PLY is no longer be released in any
 package-installable format. If you want to use the latest version, you
 need to COPY the contents of the ply/ directory into your own project
 and use it. Although PLY is no longer distributed as a package, it is
-maintained as a mature library.  No new features are planned, but 
-issues and pull requests for bugs are still welcome. Any changes to the 
+maintained as a mature library.  No new major features are planned, but 
+issues reported for bugs are still welcome. Any changes to the 
 software will be noted here.
 
+Version 4.0 (In progress)
+-------------------------
+Note: The 4.0 series of PLY represents a massive cleanup and modernization
+effort.  At a fundamental level, no new "features" are being added.  
+Instead, a lot of outdated, inconsistent, and problematic features are
+being eliminated.  Here is a short summary:
+
+   - PLY no longer writes table files or cached data.  If you want this,
+     it's your responsibility to serialize the parser tables.  Use pickle.
+
+   - Elimination of side-effects and global variables (generally).
+
+   - Elimination of numerous optional features in an effort to 
+     simplify the API.
+
+   - More use of modern Python features including iterators/generators,
+     keyword-only arguments, f-strings, etc.
+
+   - Dropped support for Python 2.x
+------------------------
+
+01/26/20  PLY no longer writes cached table files.  Honestly, the use of
+          the cached files made more sense when I was developing PLY on
+          my 200Mhz PC in 2001. It's not as much as an issue now. For small
+          to medium sized grammars, PLY should be almost instantaneous. 
+          If you're working with a large grammar, you can arrange
+          to pickle the associated grammar instance yourself if need be.
+          The removal of table files eliminated a large number of optional
+          arguments to yacc() concerning the names and packages of these files.
+
+01/26/20  PLY no longer supports Python 2.x.
+
 01/01/20  Added an install.py script to make it easy to install PLY into
           virtual environment if you just want to play with it.
 

CONTRIBUTING.md

@@ -3,19 +3,5 @@ Contributing to PLY
 
 PLY is a mature project. However, if you feel that you have found a
 bug in PLY or its documentation, please submit an issue in the form
-of a bug report.
-
-Important note: The Github repo for PLY always contains the most
-up-to-date version of the software.  If you want to use the current
-version, you should COPY the contents of the `ply/` directory into
-your own project and use it.  PLY is free software for you to use,
-but it is not maintained as a package that you install using pip
-or similar tools.
-
-
-
-
-
-
-
-
+of a bug report at https://github.com/dabeaz/ply.  Pull requests
+to the project are not accepted. 

README.md

@@ -93,7 +93,7 @@ virtual environment.
 
 PLY has no third-party dependencies. 
 
-The file doc/ply.html contains complete documentation on how to use
+The docs/ directory contains complete documentation on how to use
 the system.
 
 The example directory contains several different examples including a
@@ -176,7 +176,7 @@ def t_newline(t):
     t.lexer.lineno += t.value.count("\n")
 
 def t_error(t):
-    print("Illegal character '%s'" % t.value[0])
+    print(f"Illegal character {t.value[0]!r}")
     t.lexer.skip(1)
 
 # Build the lexer
@@ -228,18 +228,18 @@ def p_expression_name(p):
     try:
         p[0] = names[p[1]]
     except LookupError:
-        print("Undefined name '%s'" % p[1])
+        print(f"Undefined name {p[1]!r}")
         p[0] = 0
 
 def p_error(p):
-    print("Syntax error at '%s'" % p.value)
+    print(f"Syntax error at {p.value!r}")
 
 import ply.yacc as yacc
 yacc.yacc()
 
 while True:
     try:
-        s = raw_input('calc > ')   # use input() on Python 3
+        s = input('calc > ')
     except EOFError:
         break
     yacc.parse(s)