def analyze(exp):
"""analyze(exp) -> lambda env, cont: ...
Given an expression, returns a new lambda function that can be applied
on an environment and continuation."""
if expressions.isSelfEvaluating(exp):
return analyzeSelfEvaluating(exp)
if expressions.isVariable(exp):
return analyzeVariable(exp)
if expressions.isQuoted(exp):
return analyzeQuoted(exp)
if expressions.isAssignment(exp):
return analyzeAssignment(exp)
if expressions.isDefinition(exp):
return analyzeDefinition(exp)
if expressions.isIf(exp):
return analyzeIf(exp)
if expressions.isLambda(exp):
return analyzeLambda(exp)
if expressions.isBegin(exp):
return analyzeBegin(exp)
## Application checking must come last, after all the special forms.
## have been tested.
if expressions.isApplication(exp):
return analyzeApplication(exp)
## And if we get here, bad things have happened.
raise SchemeError, ("Unknown expression type -- eval " +
expressions.toString(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 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)