:- use_module(library(dcg_util)).

% DCG rules needed for describing a rudimentary CSV syntax:
% "hello","two words"
comma --> ",".
quote --> "\"".
non_quote(C) --> [C], { C \= 0'" }. % '
column(W) --> quote, generous(non_quote,W), quote, !.

:- use_module(library(tap)).

'csv: parsing' :-
    Text = `"hello","two words"`,
    once(phrase(list(column,comma,Words), Text)),
    Words == [`hello`, `two words`].

'csv: generating' :-
    once(phrase(list(column,comma,[`first`,`2nd one`,`third`]),Text)),
    Text == `"first","2nd one","third"`.

'no trailing blank elements' :-
    Text = `"one","two",`,
    once(phrase(list(column,comma,Words),Text,Rest)),
    Words == [`one`,`two`],
    Rest == `,`.

'backtracking behavior' :-
    Text = `"one","two","three"`,
    findall(Xs,phrase(list(column,comma,Xs),Text,_),Elems),
    Elems == [
        [`one`,`two`,`three`],
        [`one`,`two`],
        [`one`]
    ].