Custom data structure syntax in Prolog -

in prolog, [h|t] list begins h , remaining elements in list t (internally represented '.'(h, '.'(…))).

is possible define new syntax in similar fashion? example, possible define [t~h] list ends h , remaining elements in list t, , use freely [h|t] in heads , bodies of predicates? possible define e.g. <h|t> different structure lists?

one can interpret question literally. list-like data structure, accessing tail can expressed without auxiliary predicate. well, these minus-lists used in first prolog system — 1 called prolog 0 , written in algol-w. example the original report, p.32 transliterated iso prolog:

t(x-a-l, x-a-u-x).   ?- t(nil-m-e-t-a-l, pluriel). pluriel = nil-m-e-t-a-u-x. 

so take left-associative operator.

but, suspect, that's not wanted. want extension lists.

there have been several attempts this, 1 more recent prolog iii/prolog iv. however, quite similar constraints, have face how define equality on these operators. in other words, need go beyond syntactic unification e-unification. problem sounds easy in beginning frightening complex. simple example in prolog iv:

>> l = [a] o m, l = m o [z]. m ~ list, l ~ list. 

clearly inconsistency. is, system should respond false. there no such m, prolog iv not able deduce this. have solve @ least such problems or along them somehow.

in case want dig this, consider research started j. makanin's pioneering work:

^{problem of solvability of equations in free semi-group, akad. nauk sssr, vol.233, no.2, 1977.}

that said, might case there simpler way want. maybe associative list operator not needed.

nevertheless, not expect expressiveness such extension compared have in prolog, dcgs. in particular, general left-recursion still problem termination in grammars.