The list [[a,b]|c] in Prolog -

during exploration of different ways write down lists, intrigued following list [[a,b]|c] appears in book 'prolog , natural language analysis' pereira , shieber (page 42 of digital edition).

at first thought such notation syntactically incorrect, have had [[a,b]|[c]], after using write_canonical/1 prolog returned '.'('.'(a,'.'(b,[])),c).

as far can see, corresponds following tree structure (although seems odd me structure end c, without empty list @ end):

i cannot seem find corresponding notation using comma's , brackets though. thought correspond [[a,b],c] (but returns different result write_canonical/1).

is there no corresponding notation [[a,b]|c] or looking @ wrong way?

i cannot seem find corresponding notation using comma's , brackets though.

there no corresponding notation, since technically speaking not real list.

prolog has syntacical sugar lists. list in prolog is, lisp list, linked list: every element either empty list [], or node .(h,t) h head , t tail. lists not "special" in prolog in sense intepreter handles them differently other term. of course lot of prolog libraries list processing, , use convention defined above.

to make complex lists more convenient, syntactical sugar invented. can write node .(h,t) [h|t] well. means in [[a,b]|c]. have outer list, has 1 node .(h,c) , ? another list, 2 nodes , empty list h = .(a,.(b,[])).

technically speaking not consider "real" list, since tail of list should have either node ./2, or empty list.

you can use variables like: [[a,b]|c] in order unify tail c further. here have sort of list [a,b] first element (so list containing list) , open tail c. if later instance ground c c = [], list [[a,b]].