---input---
partition([], _, [], []).
partition([X|Xs], Pivot, Smalls, Bigs) :-
    (   X @< Pivot ->
        Smalls = [X|Rest],
        partition(Xs, Pivot, Rest, Bigs)
    ;   Bigs = [X|Rest],
        partition(Xs, Pivot, Smalls, Rest)
    ).

quicksort([])     --> [].
quicksort([X|Xs]) --> 
    { partition(Xs, X, Smaller, Bigger) },
    quicksort(Smaller), [X], quicksort(Bigger).

---tokens---
'partition'   Name.Function
'('           Punctuation
'['           Punctuation
']'           Punctuation
','           Punctuation
' '           Text
'_'           Keyword
','           Punctuation
' '           Text
'['           Punctuation
']'           Punctuation
','           Punctuation
' '           Text
'['           Punctuation
']'           Punctuation
')'           Punctuation
'.'           Punctuation
'\n'          Text

'partition'   Name.Function
'('           Punctuation
'['           Punctuation
'X'           Name.Variable
'|'           Punctuation
'Xs'          Name.Variable
']'           Punctuation
','           Punctuation
' '           Text
'Pivot'       Name.Variable
','           Punctuation
' '           Text
'Smalls'      Name.Variable
','           Punctuation
' '           Text
'Bigs'        Name.Variable
')'           Punctuation
' '           Text
':-'          Punctuation
'\n    '      Text
'('           Punctuation
'   '         Text
'X'           Name.Variable
' '           Text
'@<'          Literal.String.Atom
' '           Text
'Pivot'       Name.Variable
' '           Text
'->'          Literal.String.Atom
'\n        '  Text
'Smalls'      Name.Variable
' '           Text
'='           Operator
' '           Text
'['           Punctuation
'X'           Name.Variable
'|'           Punctuation
'Rest'        Name.Variable
']'           Punctuation
','           Punctuation
'\n        '  Text
'partition'   Name.Function
'('           Punctuation
'Xs'          Name.Variable
','           Punctuation
' '           Text
'Pivot'       Name.Variable
','           Punctuation
' '           Text
'Rest'        Name.Variable
','           Punctuation
' '           Text
'Bigs'        Name.Variable
')'           Punctuation
'\n    '      Text
';'           Punctuation
'   '         Text
'Bigs'        Name.Variable
' '           Text
'='           Operator
' '           Text
'['           Punctuation
'X'           Name.Variable
'|'           Punctuation
'Rest'        Name.Variable
']'           Punctuation
','           Punctuation
'\n        '  Text
'partition'   Name.Function
'('           Punctuation
'Xs'          Name.Variable
','           Punctuation
' '           Text
'Pivot'       Name.Variable
','           Punctuation
' '           Text
'Smalls'      Name.Variable
','           Punctuation
' '           Text
'Rest'        Name.Variable
')'           Punctuation
'\n    '      Text
')'           Punctuation
'.'           Punctuation
'\n\n'        Text

'quicksort'   Name.Function
'('           Punctuation
'['           Punctuation
']'           Punctuation
')'           Punctuation
'     '       Text
'-->'         Punctuation
' '           Text
'['           Punctuation
']'           Punctuation
'.'           Punctuation
'\n'          Text

'quicksort'   Name.Function
'('           Punctuation
'['           Punctuation
'X'           Name.Variable
'|'           Punctuation
'Xs'          Name.Variable
']'           Punctuation
')'           Punctuation
' '           Text
'-->'         Punctuation
' \n    '     Text
'{'           Punctuation
' '           Text
'partition'   Name.Function
'('           Punctuation
'Xs'          Name.Variable
','           Punctuation
' '           Text
'X'           Name.Variable
','           Punctuation
' '           Text
'Smaller'     Name.Variable
','           Punctuation
' '           Text
'Bigger'      Name.Variable
')'           Punctuation
' '           Text
'}'           Punctuation
','           Punctuation
'\n    '      Text
'quicksort'   Name.Function
'('           Punctuation
'Smaller'     Name.Variable
')'           Punctuation
','           Punctuation
' '           Text
'['           Punctuation
'X'           Name.Variable
']'           Punctuation
','           Punctuation
' '           Text
'quicksort'   Name.Function
'('           Punctuation
'Bigger'      Name.Variable
')'           Punctuation
'.'           Punctuation
'\n'          Text