def teval(exp, env, cont):
"""Evaluates an expression 'exp' in an environment 'env'.
Exercise 4.3 asks us to rewrite this in a more natural
data-directed manner. Pychecker, also, doesn't like seeing
so many 'return' statements in one function. *grin*
"""
if expressions.isSelfEvaluating(exp):
return pogo.bounce(cont, exp)
if expressions.isVariable(exp):
return pogo.bounce(cont, environment.lookupVariableValue(exp, env))
if expressions.isQuoted(exp):
return evalQuoted(exp, env, cont)
if expressions.isAssignment(exp):
return evalAssignment(exp, env, cont)
if expressions.isDefinition(exp):
return evalDefinition(exp, env, cont)
if expressions.isIf(exp):
return evalIf(exp, env, cont)
if expressions.isLambda(exp):
return pogo.bounce(cont, expressions.makeProcedure
(expressions.lambdaParameters(exp),
expressions.lambdaBody(exp),
env))
if expressions.isBegin(exp):
return evalSequence(expressions.beginActions(exp), env, cont)
if expressions.isApplication(exp):
return evalApplication(exp, env, cont)
raise SchemeError, "Unknown expression type -- eval " + str(exp)
def teval(exp, env, cont):
"""Evaluates an expression 'exp' in an environment 'env'.
Exercise 4.3 asks us to rewrite this in a more natural
data-directed manner. Pychecker, also, doesn't like seeing
so many 'return' statements in one function. *grin*
"""
if expressions.isSelfEvaluating(exp):
return pogo.bounce(cont, exp)
if expressions.isVariable(exp):
return pogo.bounce(cont, environment.lookupVariableValue(exp, env))
if expressions.isQuoted(exp):
return evalQuoted(exp, env, cont)
if expressions.isAssignment(exp):
return evalAssignment(exp, env, cont)
if expressions.isDefinition(exp):
return evalDefinition(exp, env, cont)
if expressions.isIf(exp):
return evalIf(exp, env, cont)
if expressions.isLambda(exp):
return pogo.bounce(
cont,
expressions.makeProcedure(expressions.lambdaParameters(exp),
expressions.lambdaBody(exp), env))
if expressions.isBegin(exp):
return evalSequence(expressions.beginActions(exp), env, cont)
if expressions.isApplication(exp):
return evalApplication(exp, env, cont)
raise SchemeError, "Unknown expression type -- eval " + str(exp)
def analyzed(env, cont):
return pogo.bounce(cont,
expressions.makeProcedure(params,
analyzedBody,
env))