CODEWITHSUNDEEP
prolog
YoYoYOOOO
YoYoYOOOO

Reputation: 3

Prolog: Find Minimum again and again until the list is empty

How can I repeatedly extract minimum number until the list is empty?

I want to find a minimum number, then exclude it from the original list, then find a minimum again and again, until the list becomes empty.

Input:

?- Find_Minimum([2, 1, 4, 3, 5], C)

Output:

C = 1
C = 2
C = 3
C = 4
C = 5
False

Upvotes: 0

Views: 44

Answers (2)

CapelliC
CapelliC

Reputation: 60014

I would had written - more or less - the same answer as @damianodamiano (+1), but tried nevertheless to code something more 'direct' than sorting. It turns out the outcome is rather technical...

:- module(minext, [minext/2,minext/3]).

minext(L,M) :-
    minext(L,T,R),
    (   M=T
    ;   minext(R,M)
    ).

minext(L,X,R) :-
    select(X,L,R),
    \+((
        member(Y,R),
        Y<X
    )), !.

Upvotes: 0

damianodamiano
damianodamiano

Reputation: 2662

Here a simple solution using sort/2 (in SWI):

minimum(L,E):-
    sort(L,LSorted),
    pick(LSorted,E).
pick([H|_],H).
pick([_|T],E):-
    pick(T,E).

?- minimum([2,1,4,3,5],E).
E = 1
E = 2
E = 3
E = 4
E = 5
false

Keep in mind that sort/2 removes duplicates. If you want to keep them use for instance msort/2 (in SWI). For an even simpler solution you can use member/2:

minimum(L,E):-
    sort(L,LSorted),
    member(E,LSorted).

?- minimum([2,1,4,3,5],E).
E = 1
E = 2
E = 3
E = 4
E = 5

Upvotes: 1

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