improved tree parser

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@74 014f5005-505e-4b48-8d0a-63407b615a7c

optimizer.py

@@ -26,6 +26,9 @@ 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
@@ -33,11 +36,77 @@ class node (object):
         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
             
-        for i in list(expression):
+            if level!=0:
-            print i
+                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):
@@ -45,11 +114,19 @@ class node (object):
         elif (self.kind==UNARY):
             return self.name + " "+ self.prop+ " (" + self.child +")"
         elif (self.kind==BINARY):
-            return "("+ self.left + ") " + self.name + " (" + self.right+ ")"
+            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"(a ᑌ b) ᑌ c ᑌ d")
+    n=node(u"π a,b (d-a*b)")
-print n
+    print n.__str__()