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converting tokenized expression into tree

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git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@129 014f5005-505e-4b48-8d0a-63407b615a7c
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LtWorf 2009-04-28 18:21:43 +00:00
parent 169f809988
commit 0ff9ed22a0
1 changed files with 36 additions and 12 deletions
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48
relational/optimizer.py
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@ -20,16 +20,38 @@
'''This module optimizes relational expressions into ones that require less time to be executed '''This module optimizes relational expressions into ones that require less time to be executed
For now it is highly experimental, and it shouldn't be used in 3rd party applications.''' For now it is highly experimental, and it shouldn't be used in 3rd party applications.'''
RELATION=0
UNARY=1
BINARY=2
b_operators=('*','-','ᑌ','ᑎ','ᐅᐊ','ᐅLEFTᐊ','ᐅRIGHTᐊ','ᐅFULLᐊ')
u_operators=('π','σ','ρ')
class node (object): class node (object):
'''This class is a node of a relational expression. Leaves are relations and internal nodes are operations.''' '''This class is a node of a relational expression. Leaves are relations and internal nodes are operations.'''
kind=None
RELATION=0
UNARY=1
BINARY=2
def __init__(self,expression): def __init__(self,expression):
'''Generates the tree from the tokenized expression'''
if len(expression)==1:
print "Relation: ",expression[0]
self.kind=RELATION
self.name=expression[0]
return
for i in range(len(expression)-1,-1,-1): #Expression from right to left
if expression[i] in b_operators: #Binary operator
print "Operator: ",expression[i]
print "left subtree: ",expression[:i]
print "right subtree: ",expression[i+1:]
self.kind=BINARY
self.name=expression[i]
self.left=node(expression[:i])
self.right=node(expression[i+1:])
return
elif expression[i] in u_operators: #Unary operator
self.kind=UNARY
return
pass pass
def __str__(self): def __str__(self):
@ -39,15 +61,15 @@ class node (object):
return self.name + " "+ self.prop+ " (" + self.child +")" return self.name + " "+ self.prop+ " (" + self.child +")"
elif (self.kind==BINARY): elif (self.kind==BINARY):
if self.left.kind==RELATION: if self.left.kind==RELATION:
left=self.left.__str__() le=self.left.__str__()
else: else:
left=u"("+self.left.__str__()+u")" le="("+self.left.__str__()+")"
if self.right.kind==RELATION: if self.right.kind==RELATION:
right=self.right.__str__() re=self.right.__str__()
else: else:
right=u"("+self.right.__str__()+u")" re="("+self.right.__str__()+")"
return (left+ self.name +right) return (le+ self.name +re)
def tokenize(expression): def tokenize(expression):
'''This function converts an expression into a list where '''This function converts an expression into a list where
@ -77,8 +99,6 @@ def tokenize(expression):
''' '''
while len(expression)>0: while len(expression)>0:
print "Expression", expression
print "Items" ,items
if expression.startswith('('): #Parenthesis state if expression.startswith('('): #Parenthesis state
state=2 state=2
par_count=0 #Count of parenthesis par_count=0 #Count of parenthesis
@ -136,10 +156,14 @@ def tree(expression):
pass pass
if __name__=="__main__": if __name__=="__main__":
#n=node(u"((a ᑌ b) - c ᑌ d) - b") #n=node(u"((a ᑌ b) - c ᑌ d) - b")
#n=node(u"((((((((((((2)))))))))))) - (3 * 5) - 2") #n=node(u"((((((((((((2)))))))))))) - (3 * 5) - 2")
#n=node(u"π a,b (d-a*b)") #n=node(u"π a,b (d-a*b)")
#print n.__str__() #print n.__str__()
print tokenize("((a ᑌ b) - c ᑌ d) ᐅRIGHTᐊ a * (π a,b (a))") #a= tokenize("((a ᑌ b) - c ᑌ d) ᐅRIGHTᐊ a * (π a,b (a))")
a=tokenize("a*b-c")
print a
print node(a)
#print tokenize("(a)") #print tokenize("(a)")