Next, I'd like to ask that anyone interested in parsing stuff
in python try my python parser generator available from
ftp site ftp.markv.com in the directory pub/python in the
kwParsing.* files.
This package may be appropriate for experimental translators, code
generators, interpreters, or compilers; for instructinal purposes;
among other possibility. The documentation gives a brief introduction
to the conventions and basic ideas of parsing.
Please take a look and let me know if you try it.
Aaron Watters
Department of Computer and Information Sciences
New Jersey Institute of Technology
University Heights
Newark, NJ 07102
phone (201)596-2666
fax (201)596-5777
home phone (908)545-3367
email: aaron@vienna.njit.edu
PS: As previously posted on another thread, here are some declarations
that build a parser for lisp lists with printing and variables.
=====
import string
GRAMMARSTRING ="""
Value :: ## indicates Value is the root nonterminal for the grammar
@R SetqRule :: Value >> ( setq var Value )
@R ListRule :: Value >> ( ListTail
@R TailFull :: ListTail >> Value ListTail
@R TailEmpty :: ListTail >> )
@R Varrule :: Value >> var
@R Intrule :: Value >> int
@R Strrule :: Value >> str
@R PrintRule :: Value >> ( print Value )
"""
COMPILEDFILENAME = "TESTLispG.py"
LISPCOMMENTREGEX = ";.*"
INTREGEX = "["+string.digits+"]+"
STRREGEX = '"[^\n"]*"'
VARREGEX = "["+string.letters+"]["+string.letters+string.digits+"]*"
### declare interpretation functions and regex's for terminals
def intInterp( str ):
return string.atoi(str)
def stripQuotes( str ):
return str[1:len(str)-1]
def echo(string):
return string
def DeclareTerminals(Grammar):
Grammar.Addterm("int", INTREGEX, intInterp)
Grammar.Addterm("str", STRREGEX, stripQuotes)
Grammar.Addterm("var", VARREGEX, echo)
### declare the rule reduction interpretation functions.
def EchoValue( list, Context ):
return list[0]
def VarValue( list, Context ):
varName = list[0]
if Context.has_key(varName):
return Context[varName]
else:
raise NameError, "no such lisp variable in context "+varName
def NilTail( list, Context ):
return []
def AddToList( list, Context ):
return [ list[0] ] + list[1]
def MakeList( list, Context ):
return list[1]
def DoSetq( list, Context):
Context[ list[2] ] = list[3]
return list[3]
def DoPrint( list, Context ):
print list[2]
return list[2]
def BindRules(Grammar):
Grammar.Bind( "Intrule", EchoValue )
Grammar.Bind( "Strrule", EchoValue )
Grammar.Bind( "Varrule", VarValue )
Grammar.Bind( "TailEmpty", NilTail )
Grammar.Bind( "TailFull", AddToList )
Grammar.Bind( "ListRule", MakeList )
Grammar.Bind( "SetqRule", DoSetq )
Grammar.Bind( "PrintRule", DoPrint )
# This function generates the grammar and dumps it to a file.
def GrammarBuild():
import kjParseBuild
LispG = kjParseBuild.NullCGrammar()
LispG.SetCaseSensitivity(0) # grammar is not case sensitive for keywords
DeclareTerminals(LispG)
LispG.Keywords("setq print")
LispG.punct("().")
LispG.Nonterms("Value ListTail")
LispG.comments([LISPCOMMENTREGEX])
LispG.Declarerules(GRAMMARSTRING)
LispG.Compile()
outfile = open(COMPILEDFILENAME, "w")
LispG.Reconstruct("LispG",outfile,"GRAMMAR")
outfile.close()
BindRules(LispG)
return LispG
# this function initializes the compiled grammar from the generated file.
def LoadLispG():
import TESTLispG
# reload to make sure we get the most recent version!
# (only needed when debugging the grammar).
reload(TESTLispG)
LispG = TESTLispG.GRAMMAR()
DeclareTerminals(LispG)
BindRules(LispG)
return LispG
########## test the grammar generation
Dummy = GrammarBuild()
LispG = LoadLispG()
### declare an initial context, and do some tests.
Context = { 'x':3 }
test1 = LispG.DoParse1( '()', Context)
test2 = LispG.DoParse1( '(123)', Context)
test3 = LispG.DoParse1( '(x)', Context)
test4 = LispG.DoParse1( '" a string "', Context)
test5 = LispG.DoParse1( '(setq y (1 2 3) )', Context )
test6 = LispG.DoParse1( '(SeTq x ("a string" "another" 0))', Context )
test7str = """
; this is a lisp comment
(setq abc (("a" x)
("b" (setq d 12))
("c" y) ) ; another lisp comment
)
"""
test7 = LispG.DoParse1( test7str, Context)
test8 = LispG.DoParse1( '(print (1 x d))', Context)