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teaching
AI
Commits
1b495d59
Commit
1b495d59
authored
Nov 01, 2019
by
jfschaefer
Browse files
Merge branch 'master' of gl.kwarc.info:teaching/AI
parents
d96f3152
6a7f22be
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2
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Leon/tut1/examples.pl
0 → 100644
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1b495d59
peter
.
%? peter.
likes
(
peter
,
mary
).
likes
(
peter
,
sophie
).
cool
(
X
)
:
likes
(
peter
,
X
).
%? trace, cool(sophie).
%? trace, cool(X).
has_wheels
(
mybike
,
2
).
has_wheels
(
mytricycle
,
3
).
has_wheels
(
mytoycar
,
4
).
has_wheels
(
mycar
,
4
).
has_motor
(
mybike
).
has_motor
(
mycar
).
car
(
X
)
:
has_wheels
(
X
,
4
),
has_motor
(
X
).
%? trace, car(Y).
% Cool cool cool, but how can we code with this?
% The answers is for the most part...RECURSION!
nat
(
zero
).
nat
(
s
(
X
))
:
nat
(
X
).
% add(X, Y, Z) > X + Y = Z
add
(
X
,
zero
,
X
).
add
(
X
,
s
(
Y
),
s
(
Z
))
:
add
(
X
,
Y
,
Z
).
% We see, there is no "return" in Prolog, only predicates.
% For every predicate please state in a comment which parameters
% are input and which are output.
%% List comprehension:
% list e.g. [1,2,3] or [jamie,cersei], empty list = []
% pattern matching with lists:
% [HeadTail], where Head is an element and Tail is a List!
% Also works with first 2 elements [X1, X2  T]
append
([],
L2
,
L2
).
append
([
H

T
],
L2
,[
H

Res
]):
append
(
T
,
L2
,
Res
).
% A practical example
% Signature for our problem:
% countN(N : int, L : List[int]) > int
% counts the occurrences of N in L and returns the result.
% With Prologlike lists: countN(N, [H  T]) > int
% L = [2, 3, 5, 2, 7, 1, 2, 2, 5, 9]
% countN(3, L) > 1
% countN(2, L) > 4
% countN(8, L) > 0
% countN(5, L) > 2
% Delcarative Approach
% countN(N, L) > res
% res = 0
% for e in L:
% if e == N:
% res += 1
% return res
% Functional / Recursive Approach
% Base Cases:
% countN(N, []) > return 0
% Recursive Case:
% countN(N, [H  T]) >
% if N == H
% return countN(N, [T]) + 1
% else
% return countN(N, [T])
% ... in prolog we can't "return", so we need another variable in the predicate
% countN(N, L, RES) the number of occurrences of N in list L
% will be "returned/safed" in RES (Will be in relation with RES)
% Base Cases:
countN
(
_
,
[],
0
).
%? trace, countN(2, [], X).
% Recursive Case:
countN
(
N
,
[
N

T
],
RES
)
:
countN
(
N
,
T
,
OLDRES
),
RES
is
OLDRES
+
1
.
countN
(
N
,
[
M

T
],
RES
)
:
not
(
N
=
M
),
countN
(
N
,
T
,
RES
).
% Point out: "N" in first line list compr. "is" can be very useful
%? trace, countN(2, [2], X).
Leon/tut1/presentationhandout.pdf
0 → 100644
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1b495d59
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