Ascend FD-23R Manual de usuario descargar pdf (Pagina 74)

62 CHAPTER C. Common Functions (ﬁle misc.toy)

false ‘or‘ false = false

% Sequential and

false /\ _ = false

true /\ X = X

% Sequential or

true \/ X = true

false \/ X = X

% Negation

not true = false

not false = true

andL, orL ,orL’ :: [bool] -> bool

andL = foldr (/\) true

orL = foldr or false

orL’ = foldr (\/) false

% orL’ is ’stricter’, but more deterministic, than orL

any, any’,all :: (A -> bool) -> [A] -> bool

any P = orL . (map P)

any’ P = orL’ . (map P)

% any’ is ’stricter’, but more deterministic, than any

all P = andL . (map P)

undefined :: A

undefined = if false then undefined

% (def X) is true if X is finite and totally defined

def X :- X == _

% (not_undef X) is true if X is not undefined

not_undef X :- X /= _

% (nf X) is the identity, restricted to finite and totally defined values

% Operationally, (nf X) forces the computation of a normal form for X,

% if it exists.

nf X = Y <== X==Y

% (hnf X) is the identity, restricted to not undefined values.

% Operationally, (hnf X) forces the computation of a head normal form for X,

% if it exists.

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Ascend FD-23R Manual de usuario Pagina 74