keysort/2¶

keysort(+ L, S)* is iso

Assuming L is a list of the form _Key_- _Value_, keysort(+ _L_, _S_) unifies S with the list obtained from L, by sorting its elements according to the value of Key.

 ?- keysort([3-a,1-b,2-c,1-a,1-b],S).

would return:

 S = [1-b,1-a,1-b,2-c,3-a]