rishi/scryer-prolog
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~| now incorporates the number of characters described so far

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Therefore, subsequent uses of ~N| now yield the specified column,
instead of potentially overshooting.

Example:

    ?- format("hello~|~t~8|!", []).
    hello   !   true.

Such cases are probably rather uncommon: Relative positioning with ~N+
is more likely to be used in such cases, and that worked as intended
also previously as it does now:

    ?- format("hello~|~t~3+!", []).
    hello   !   true.

In fact, if absolute positions are used, then ~| can be omitted entirely:

    ?- format("hello~t~8|!", []).
    hello   !   true.
This commit is contained in:
Markus Triska
2021-02-09 20:52:26 +01:00
parent 195273f01d
commit 1bdfc5a1a4
1 changed files with 12 additions and 7 deletions
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19
src/lib/format.pl
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@@ -1,5 +1,5 @@
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Written March 2020 by Markus Triska (triska@metalevel.at)
Written 2020, 2021 by Markus Triska (triska@metalevel.at)
Part of Scryer Prolog.
This library provides the nonterminal format_//2 to describe
@@ -141,7 +141,7 @@ element_gluevar(glue(_,V), N, N) --> [V].
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Our key datastructure is a list of cells and newlines.
A cell has the shape from_to(From,To,Elements), where
A cell has the shape cell(From,To,Elements), where
From and To denote the positions of surrounding tab stops.
Elements is a list of elements that occur in a cell,
@@ -263,6 +263,11 @@ cells([~,'`',Char,t|Fs], Args, Tab, Es, VNs) --> !,
cells(Fs, Args, Tab, [glue(Char,_)|Es], VNs).
cells([~,t|Fs], Args, Tab, Es, VNs) --> !,
cells(Fs, Args, Tab, [glue(' ',_)|Es], VNs).
cells([~,'|'|Fs], Args, Tab0, Es, VNs) --> !,
{ phrase(elements_gluevars(Es, 0, Width), _),
Tab is Tab0 + Width },
cell(Tab0, Tab, Es),
cells(Fs, Args, Tab, [], VNs).
cells([~|Fs0], Args0, Tab, Es, VNs) -->
{ numeric_argument(Fs0, Num, ['|'|Fs], Args0, Args) },
!,
@@ -381,15 +386,15 @@ format(Stream, Fs, Args) :-
flush_output(Stream).
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
?- phrase(cells("hello", [], 0, []), Cs).
?- phrase(format:cells("hello", [], 0, [], []), Cs).
?- phrase(cells("hello~10|", [], 0, []), Cs).
?- phrase(cells("~ta~t~10|", [], 0, []), Cs).
?- phrase(format:cells("hello~10|", [], 0, [], []), Cs).
?- phrase(format:cells("~ta~t~10|", [], 0, [], []), Cs).
?- phrase(format_("~`at~50|", []), Ls).
?- phrase(cells("~`at~50|", [], 0, []), Cs),
phrase(format_cells(Cs), Ls).
?- phrase(format:cells("~`at~50|", [], 0, [], []), Cs),
phrase(format:format_cells(Cs), Ls).
?- phrase(format:cells("~ta~t~tb~tc~21|", [], 0, [], []), Cs).
Cs = [cell(0,21,[glue(' ',_A),chars("a"),glue(' ',_B),glue(' ',_C),chars("b"),glue(' ',_D),chars("c ...")])]
?- phrase(format:cells("~ta~t~4|", [], 0, [], []), Cs).