Modernization/fixes such as updates for Python 3

README.md

@@ -1,8 +1,9 @@
 # PL/0 Language Tools
 
 The PL/0 Language Tools serve as an example of how to construct a
-compiler. The language 'PL/0' was originally introduced in the book
-"Algorithms + Data Structures = Programs", by Niklaus Wirth in 1975.
+compiler. The language [PL/0](https://en.wikipedia.org/wiki/PL/0) was
+originally introduced in the book "Algorithms + Data Structures = Programs",
+by Niklaus Wirth in 1975.
 
 ![Overview](Overview.png)
 
@@ -15,19 +16,42 @@ It is designed to be clear and concise at the expense of performance. It
 is easy to extend and modify, e.g. adding new syntax constructs or
 machine instructions.
 
-## Installation
+## Install dependencies
 
-Install ply:
+* The [ply](https://www.dabeaz.com/ply/) Python library is used for lexical analysis and parsing.
 
-	sudo easy_install ply
+Optional:
+* It is recommended to use the [xdot](https://github.com/jrfonseca/xdot.py#readme) program to view the abstract syntax tree. If `xdot` isn't available, the PDF viewer `evince` is used as a fallback.
 
-Then, simply download the files `pl0_*.py` and run them.
+### Fedora
+
+	dnf install -y python-ply python-xdot evince
+
+### Debian/Ubuntu
+
+	apt update && apt install -y python-is-python3 python3-ply
+
+### Unix-based
+
+Package names may be similar to the ones above.
+
+For macOS it is possible to use the [Homebrew](https://brew.sh/) installer.
+
+### Windows
+
+Open a Command Prompt (press Win + R, type `cmd`) and install Python.
+
+	winget install Python
+
+Use [pip](https://pip.pypa.io/) to install the ply library.
+
+	pip install ply
 
 ## Basic Usage
 
 Here is a full example using the interpreter:
 
-	$ ./pl0_interpreter.py < examples/fibonacci.pl1
+	$ python pl0_interpreter.py < examples/fibonacci.pl0
 	1
 	1
 	2
@@ -51,14 +75,46 @@ Here is a full example using the interpreter:
 	10946
 	-- Stack Frame --
 	Constants: {'K': 20}
-	Variables: {'count': 21, 'k': 17711, 'm': 17711, 'n': 28657}
+	Variables: {'m': 17711, 'n': 28657, 'k': 17711, 'count': 21}
 	Procedures: {}
 
-If you want to see a abstract syntax tree of your program, use the pl0_graphviz.py command:
+Example of using the compiler, assembler and virtual machine:
+
+	$ python pl0_compiler.py < examples/fibonacci.pl0 | python pl0_assembler.py | python pl0_machine.py
+	1
+	1
+	2
+	3
+	5
+	8
+	13
+	21
+	34
+	55
+	89
+	144
+	233
+	377
+	610
+	987
+	1597
+	2584
+	4181
+	6765
+	10946
+	-- Machine State --
+	Sequence: [16, 6, 17711, 28657, 17711, 21, 10, 1, 7, 2, 10, 1, 7, 3, 10, 1, 7, 4, 10, 0, 7, 5, 6, 5, 10, 20, 31, 22, 57, 6, 4, 50, 11, 6, 3, 7, 4, 6, 2, 6, 3, 45, 7, 3, 6, 4, 7, 2, 6, 5, 10, 1, 45, 7, 5, 16, 22, 1]
+	Stack: []
+	Offset: -1
+
+To see the result of lexical analysis and parsing:
+
+	python pl0_lexer.py < examples/fibonacci.pl0
+	python pl0_parser.py < examples/fibonacci.pl0
 
-	./pl0_graphviz.py < examples/fibonacci.pl1
+To get a graphical view of the abstract syntax tree:
 
-A sample graph is included in the `examples` directory.
+	python pl0_graphviz.py < examples/fibonacci.pl0
 
 For more advanced usage, including documentation on individual components, please see the [online documentation](http://programming.dojo.net.nz/study/pl0-language-tools/index).
 

expect/fibonacci.run

@@ -21,5 +21,5 @@
 10946
 -- Stack Frame --
 Constants: {'K': 20}
-Variables: {'count': 21, 'k': 17711, 'm': 17711, 'n': 28657}
+Variables: {'m': 17711, 'n': 28657, 'k': 17711, 'count': 21}
 Procedures: {}

pl0_ansforth.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (c) 2012 Michal J Wallace. <http://www.michaljwallace.com/>
 # Copyright (c) 2012 Charles R Childers
@@ -29,7 +29,7 @@
 from pl0_node_visitor import StackingNodeVisitor
 import sys
 import pl0_parser
-import StringIO
+import io
 import os
 import types
 
@@ -51,7 +51,7 @@
     'NE'     : '<>',
 }
 
-UNKNOWN, VAR, CONST, PROCEDURE = range(4)
+UNKNOWN, VAR, CONST, PROCEDURE = list(range(4))
 CATEGORY = "UNKNOWN VAR CONST PROCEDURE".split()
 
 
@@ -84,7 +84,7 @@ def local_vars(self):
         returns a list of names of variables to preserve
         when calling functions recursively
         """
-        return [ key for (key, (kind, _)) in self.local_defs.items()
+        return [ key for (key, (kind, _)) in list(self.local_defs.items())
                  if kind == VAR ]
 
     def lookup(self, name):
@@ -106,19 +106,19 @@ def visit( self, node ):
 
     def accept_number(self, nid, value):
         if self.negate:
-            print "-{0}".format(value),
+            print("-{0}".format(value), end=' ')
             self.negate = False
         else:
             sys.stdout.write(" ")
-            print value,
+            print(value, end=' ')
 
     # logically, print ("!") would come much later
     # but i'm putting these in implementation order,
     # and i want this up front so i can see the
     # results of running the code.
     def accept_print(self, nid, expr):
         self.visit( expr )
-        print ' . ',
+        print(' . ', end=' ')
 
     #-- expressions --------------------
 
@@ -131,7 +131,7 @@ def accept_term( self, nid, *factors_tup ):
         self.visit( factors.pop( 0 ))
         for operator, operand in factors:
             self.visit( operand )
-            print ops[ operator ],
+            print(ops[ operator ], end=' ')
 
     # expression = [ "+"|"-"] term { ("+"|"-") term}.
     def accept_expression(self, nid, sign, *terms_tup):
@@ -154,10 +154,10 @@ def accept_expression(self, nid, sign, *terms_tup):
             else:
                 operator, term = node
                 self.visit( term )
-                print ops[ operator ],
+                print(ops[ operator ], end=' ')
 
         if negate_after:
-            print "-1 *",
+            print("-1 *", end=' ')
 
     #-- named constants ----------------
 
@@ -184,7 +184,7 @@ def accept_name(self, nid, name):
 
     def accept_variables(self, nid, *names):
         for nid, name in names:
-            print "variable " + name + "\n",
+            print("variable " + name + "\n", end=' ')
             self.local_defs[ name ] = (VAR, name)
 
     def accept_set(self, nid, name, expr):
@@ -198,7 +198,7 @@ def accept_set(self, nid, name, expr):
 
     def accept_odd(self, nid, expr):
         self.visit( expr )
-        print "2 mod 1 =",
+        print("2 mod 1 =", end=' ')
 
     def accept_condition(self, nid, lhs, rel, rhs):
         self.visit( lhs )
@@ -228,11 +228,11 @@ def accept_while(self, nid, cond, stmt):
         #    <cond> [ [ <stmt> <cond> ] while ] ifTrue
         #
         # TODO: lower level/faster WHILE implementation
-        print " begin ",
+        print(" begin ", end=' ')
         self.visit( cond )
-        print " while ",
+        print(" while ", end=' ')
         self.visit( stmt )
-        print " repeat ",
+        print(" repeat ", end=' ')
 
 
     #-- procedures ---------------------
@@ -245,7 +245,7 @@ def accept_program(self, nid, block):
         self.visit(stmt)
         sys.stdout.write(" ;\n")
 
-        print "run\n"
+        print("run\n")
 
 
     # for recursion, we need to maintain a stack
@@ -271,14 +271,14 @@ def accept_call(self, nid, name):
         #TODO: only push/pop shadowed variables
         recursive = name in self.proc_path
 
-        def call(): print name,
+        def call(): print(name, end=' ')
 
         keep = self.local_vars()
 
         if recursive:
             for ident in keep:
                  sys.stdout.write(ident + ' @ ')
-            print " recurse ",
+            print(" recurse ", end=' ')
             for ident in reversed( keep ):
                  sys.stdout.write(ident + ' ! ')
         else:

pl0_assembler.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (c) 2012 Samuel G. D. Williams. <http://www.oriontransfer.co.nz>
 #
@@ -23,12 +23,12 @@
 
 import pl0_machine
 import sys
-import StringIO
+import io
 import re
 
-label_re = re.compile('\s*(.*?):')
-whitespace_re = re.compile('\s+')
-comment_re = re.compile('^\s*#.*$')
+label_re = re.compile(r'\s*(.*?):')
+whitespace_re = re.compile(r'\s+')
+comment_re = re.compile(r'^\s*#.*$')
 
 def is_integer(string):
     try:
@@ -59,7 +59,7 @@ def assemble(input):
             for argument in command:
                 if is_integer(argument):
                     buffer.append(int(argument))
-                elif pl0_machine.OPCODES.has_key(argument):
+                elif argument in pl0_machine.OPCODES:
                     buffer.append(pl0_machine.OPCODES[argument])
                 else:
                     # A label
@@ -70,4 +70,4 @@ def assemble(input):
 
 if __name__ == '__main__':
     code = assemble(sys.stdin)
-    print `code`
+    print(repr(code))