d59ba9f9f1
git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@74 014f5005-505e-4b48-8d0a-63407b615a7c
132 lines
4.8 KiB
Python
132 lines
4.8 KiB
Python
# coding=UTF-8
|
||
# Relational
|
||
# Copyright (C) 2008 Salvo "LtWorf" Tomaselli
|
||
#
|
||
# Relation is free software: you can redistribute it and/or modify
|
||
# it under the terms of the GNU General Public License as published by
|
||
# the Free Software Foundation, either version 3 of the License, or
|
||
# (at your option) any later version.
|
||
#
|
||
# This program is distributed in the hope that it will be useful,
|
||
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
# GNU General Public License for more details.
|
||
#
|
||
# You should have received a copy of the GNU General Public License
|
||
# along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||
#
|
||
# author Salvo "LtWorf" Tomaselli <tiposchi@tiscali.it>
|
||
|
||
'''This module optimizes relational expressions into ones that require less time to be executed'''
|
||
|
||
RELATION=0
|
||
UNARY=1
|
||
BINARY=2
|
||
|
||
class node (object):
|
||
'''This class is a node of a relational expression. Leaves are relations and internal nodes are operations.'''
|
||
def __init__(self,expression):
|
||
expression=expression.strip()
|
||
|
||
print "Parsing: ",expression
|
||
'''expression must be a valid relational algrbra expression that would be accepted by the parser
|
||
and must be utf16'''
|
||
self.kind=0
|
||
self.name="a"
|
||
self.prop=""
|
||
'''*-ᑌᑎᐅᐊᐅLEFTᐊᐅRIGHTᐊᐅFULLᐊπσρ'''
|
||
|
||
binary=(u"*",u"-",u"ᑌ",u"ᑎ")
|
||
unary=(u"π",u"σ",u"ρ")
|
||
'''(a ᑌ (a ᑌ b ᑌ c ᑌ d)) ᑎ c - σ i==3(πa,b(aᑌ b ᑎ c))'''
|
||
level=0 #Current parentesis level
|
||
start=-1 #Start of the parentesis
|
||
end=-1 #End of the parentesis.
|
||
tokens=list(expression) #Splitted expression
|
||
r=range(len(tokens))
|
||
r.reverse()
|
||
lev_non_zero_chars=0 #Number of chars inside parentesis
|
||
for i in r: #Parses expression from end to begin, to preserve operation's order
|
||
if tokens[i]==u"(":
|
||
if level==0:
|
||
start=i
|
||
print start
|
||
level+=1
|
||
elif tokens[i]==u")":
|
||
level-=1
|
||
if level==0:
|
||
end=i
|
||
print end
|
||
|
||
if level!=0:
|
||
lev_non_zero_chars+=1
|
||
|
||
if i==0 and level==0 and tokens[i] in unary: #Unary operator found, must grab its parameters and its child relation they
|
||
child=""
|
||
for q in tokens[start+1:end]:
|
||
child+=q
|
||
self.name= tokens[i]
|
||
print "-----",tokens[i]
|
||
print "---",start,end,lev_non_zero_chars
|
||
print child
|
||
#print prop
|
||
#self.child=node(child)
|
||
|
||
if level==0 and tokens[i] in binary: #Binary operator found, everything on left will go in the left subree and everhthing on the right will go in the right subtree
|
||
self.kind=BINARY
|
||
left=""
|
||
right=""
|
||
|
||
if start==end==-1:#No parentesis before
|
||
end=i
|
||
|
||
for q in tokens[start+1:end]:
|
||
left+=q
|
||
self.name= tokens[i]
|
||
for q in tokens[i+1:]:
|
||
right+=q
|
||
print "self: ",tokens[i]
|
||
print "left: ",left
|
||
print "right:" ,right
|
||
self.left=node(left)
|
||
self.right=node(right)
|
||
|
||
return
|
||
|
||
if lev_non_zero_chars!=0 and lev_non_zero_chars+1==len(expression):#Expression is entirely contained in parentesis, removing them
|
||
n=node(expression[1:-1])
|
||
self.name=n.name
|
||
self.kind=n.kind
|
||
if n.kind==UNARY:
|
||
self.child=n.child
|
||
elif n.kind==BINARY:
|
||
self.left=n.left
|
||
self.right=n.right
|
||
self.prop=n.prop
|
||
return
|
||
|
||
self.kind=RELATION
|
||
self.name=expression
|
||
|
||
def __str__(self):
|
||
if (self.kind==RELATION):
|
||
return self.name
|
||
elif (self.kind==UNARY):
|
||
return self.name + " "+ self.prop+ " (" + self.child +")"
|
||
elif (self.kind==BINARY):
|
||
if self.left.kind==RELATION:
|
||
left=self.left.__str__()
|
||
else:
|
||
left=u"("+self.left.__str__()+u")"
|
||
if self.right.kind==RELATION:
|
||
right=self.right.__str__()
|
||
else:
|
||
right=u"("+self.right.__str__()+u")"
|
||
|
||
return (left+ self.name +right)
|
||
|
||
if __name__=="__main__":
|
||
#n=node(u"((a ᑌ b) - c ᑌ d) - b")
|
||
#n=node(u"((((((((((((2)))))))))))) - (3 * 5) - 2")
|
||
n=node(u"π a,b (d-a*b)")
|
||
print n.__str__() |