def OR_handler(exp):
"""We have to consider three cases:
(OR) ===> #t
(OR e1) ===> e1
(OR e1 e2 ...) ===> (let ((temp-val e1))
(IF temp-val
temp-val
(OR e2 ...)))
===> ((lambda (temp-val)
(IF temp-val
temp-val
(OR e2 ...)))
e1)
"""
clauses = and_clauses(exp)
if pair.length(clauses) == 0:
return symbol.true
elif pair.length(clauses) == 1:
return pair.car(clauses)
else:
temporarySymbol = symbol.makeUniqueTemporary()
lambdaVal = expressions.makeLambda(
pair.list(temporarySymbol),
pair.list(expressions.makeIf(temporarySymbol,
temporarySymbol,
makeOr(pair.cdr(clauses)))))
return expressions.makeApplication(
lambdaVal, pair.list(pair.car(clauses)))
def AND_handler(exp):
"""We have to consider three cases:
(AND) ===> #f
(AND e1) ===> e1
(AND e1 e2 ...) ===> (IF e1 (AND e2 ...) #f)
"""
clauses = and_clauses(exp)
if pair.length(clauses) == 0:
return symbol.false
elif pair.length(clauses) == 1:
return pair.car(clauses)
else:
return expressions.makeIf(pair.car(clauses),
makeAnd(pair.cdr(clauses)),
symbol.false)
def isTaggedList(exp, tag):
"""Returns true if the expression is tagged with the 'tag'."""
if pair.isList(exp) and pair.length(exp) > 0:
return pair.car(exp) == tag
return 0
def operator(exp):
if pair.length(exp) == 0:
raise SchemeError, \
"No operator given for procedure application -- OPERATOR"
return pair.car(exp)
def isTaggedList(exp, tag):
"""Returns true if the expression is tagged with the 'tag'."""
if pair.isList(exp) and pair.length(exp) > 0:
return pair.car(exp) == tag
return 0
def operator(exp):
if pair.length(exp) == 0:
raise SchemeError, \
"No operator given for procedure application -- OPERATOR"
return pair.car(exp)
