Succeeds if the character represented by X is a member of the character type represented by Y. Supported character types are:
digitupper- upper case letterlower- lower case letteralpha- letter (upper or lower)alnum- letter (upper or lower) or digitwhite- whitespace
Examples
?- char_type(a, digit).
no
?- char_type(a, lower).
yes
?- char_type(a, upper).
no
?- char_type(a, alpha).
yes
?- char_type(a, alnum).
yes
?- char_type(a, white).
no
?- char_type('A', digit).
no
?- char_type('A', lower).
no
?- char_type('A', upper).
yes
?- char_type('A', alpha).
yes
?- char_type('A', alnum).
yes
?- char_type('A', white).
no
?- char_type('1', digit).
yes
?- char_type('1', lower).
no
?- char_type('1', upper).
no
?- char_type('1', alpha).
no
?- char_type('1', alnum).
yes
?- char_type('1', white).
no
?- char_type(' ', digit).
no
?- char_type(' ', lower).
no
?- char_type(' ', upper).
no
?- char_type(' ', alpha).
no
?- char_type(' ', alnum).
no
?- char_type(' ', white).
yes
?- char_type('\\t ', digit).
no
?- char_type('\\t', lower).
no
?- char_type('\\t', upper).
no
?- char_type('\\t', alpha).
no
?- char_type('\\t', alnum).
no
?- char_type('\\t', white).
yes
?- char_type(z, X).
X = alnum
yes;
X = alpha
yes;
X = lower
yes;
no
?- char_type(X, digit).
X = 0
yes;
X = 1
yes;
X = 2
yes;
X = 3
yes;
X = 4
yes;
X = 5
yes;
X = 6
yes;
X = 7
yes;
X = 8
yes;
X = 9
yes;
no
?- char_type(X, upper).
X = A
yes;
X = B
yes;
X = C
yes;
X = D
yes;
X = E
yes;
X = F
yes;
X = G
yes;
X = H
yes;
X = I
yes;
X = J
yes;
X = K
yes;
X = L
yes;
X = M
yes;
X = N
yes;
X = O
yes;
X = P
yes;
X = Q
yes;
X = R
yes;
X = S
yes;
X = T
yes;
X = U
yes;
X = V
yes;
X = W
yes;
X = X
yes;
X = Y
yes;
X = Z
yes;
no
?- char_type(X, lower).
X = a
yes;
X = b
yes;
X = c
yes;
X = d
yes;
X = e
yes;
X = f
yes;
X = g
yes;
X = h
yes;
X = i
yes;
X = j
yes;
X = k
yes;
X = l
yes;
X = m
yes;
X = n
yes;
X = o
yes;
X = p
yes;
X = q
yes;
X = r
yes;
X = s
yes;
X = t
yes;
X = u
yes;
X = v
yes;
X = w
yes;
X = x
yes;
X = y
yes;
X = z
yes;
no
?- char_type(X, alnum).
X = 0
yes;
X = 1
yes;
X = 2
yes;
X = 3
yes;
X = 4
yes;
X = 5
yes;
X = 6
yes;
X = 7
yes;
X = 8
yes;
X = 9
yes;
X = A
yes;
X = B
yes;
X = C
yes;
X = D
yes;
X = E
yes;
X = F
yes;
X = G
yes;
X = H
yes;
X = I
yes;
X = J
yes;
X = K
yes;
X = L
yes;
X = M
yes;
X = N
yes;
X = O
yes;
X = P
yes;
X = Q
yes;
X = R
yes;
X = S
yes;
X = T
yes;
X = U
yes;
X = V
yes;
X = W
yes;
X = X
yes;
X = Y
yes;
X = Z
yes;
X = a
yes;
X = b
yes;
X = c
yes;
X = d
yes;
X = e
yes;
X = f
yes;
X = g
yes;
X = h
yes;
X = i
yes;
X = j
yes;
X = k
yes;
X = l
yes;
X = m
yes;
X = n
yes;
X = o
yes;
X = p
yes;
X = q
yes;
X = r
yes;
X = s
yes;
X = t
yes;
X = u
yes;
X = v
yes;
X = w
yes;
X = x
yes;
X = y
yes;
X = z
yes;
no white_test :- char_type(X, white), write('>'), write(X), write('<'), nl, fail.
?- white_test.
>\t<
> <
no