def evaluate(self,node):
"""Evaluator function
Evaluates the parse tree rooted at the current node
Basically a giant if construct that decides what to do
based on the type of node (as found by the string at node[0])
"""
if DEBUG:
print "Evaluating",node
if self.cur_line>=len(self.parse_trees):
#reached end of the list of parse trees
return None
if node[0]=='STMT':
# statement
line=self.cur_line
self.evaluate(node[1])
if self.cur_line==line:
self.evaluate(node[-1])
elif node[0]=='DIM':
# declaration
name=node[1][1] # gets the name of the identifier only (e.g. in myvar and myvar(3,3), myvar is the name)
id_node=node[1] # parse tree rooted at id_node represents an identifier
# not specifying a data type makes it INTEGER by default
if len(node)>2:
datatype=DATA_TYPES[node[2]]
else:
datatype=DATA_TYPES['INTEGER']
# declaring two variables with the same name (or the name of a predefined function) is not allowed
if name in self.variables:
raise InterpreterError("Runtime Error: %s already declared"%name)
if len(id_node)==2:
# scalar: simply create a new Variable
var=Variable(name,datatype,datatype(0))
#print "creating scalar %s"%name,var.__class__
else:
# array: get dimensions by evaluating the list following the name and create a MultiArray
dimensions=self.evaluate(id_node[-1])
var=MultiArray(dimensions, name, datatype,datatype(0))
self.variables[name]=var
self.cur_line+=1
elif node[0]=='LET':
# assignment
varname=node[1][1] # left hand side
value=self.evaluate(node[2]) # right hand side
#print "got value ",value
#if DEBUG:
# print value
if varname not in self.variables:
rhs_type=get_type(value,value)
#print ">>>>>>",rhs_type
if len(node[1])==2:
# not an array: automatic declaration
##print "+++++",DATA_TYPES[rhs_type]
var=Variable(varname,DATA_TYPES[rhs_type],cast(DATA_TYPES[rhs_type],ctypes.c_long(0)))
#print "value: ",var.value
else:
# array
raise InterpreterError("Cannot assign to undeclared array %s: "%varname)
self.variables[varname]=var
#print "just assigned ",varname," to ", var.value.__class__
else:
var=self.variables[varname]
if len(node[1])==2:
# not an array: simple assignment
#print "type: ", var.type
#print "value: ", value
if var.type!=value.__class__:
#print "here"
var.value=var.type(REQUIRED_PY_TYPE[var.type](value.value))
else:
var.value=value
else:
# array: figure out indices first and then try to assign
coords=self.evaluate(node[1][-1])
try:
var.set_(coords,var.type(REQUIRED_PY_TYPE[var.type](value.value)))
except AttributeError,e:
raise InterpreterError("Cannot assign to %s"%varname)
#print "checking: ",self.variables[varname].value
self.cur_line+=1
