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 c_altern(alternative_value):
return pogo.bounce(cont,
expressions.makeIf(pred_value,
consequent_value,
alternative_value))
