Align columns: Difference between revisions

=={{header|Prolg}}==

Works with SWI-Prolog.<BR>

Prolog has a particular treatment for strings : any string beginning by an uppercase letter is enclosed with quotes, ditto for a word ending with a comma or a point.

<lang Prolog>aligner :-

L ="Given$a$text$file$of$many$lines,$where$fields$within$a$line$

are$delineated$by$a$single$'dollar'$character,$write$a$program

that$aligns$each$column$of$fields$by$ensuring$that$words$in$each$

column$are$separated$by$at$least$one$space.

Further,$allow$for$each$word$in$a$column$to$be$either$left$

justified,$right$justified,$or$center$justified$within$its$column.",

% read the lines and the words

% compute the length of the longuest word.

% LP is the list of lines,

% each line is a list of words

parse(L, 0, N, LP, []),

% Because of the particular treatment of the strings by Prolog

% we need to add 3 and not 1

N1 is N+3,

% words will be left aligned

sformat(AL, '%~wl', [N1]),

% words will be centered

sformat(AC, '%~wc', [N1]),

% words will be right aligned

sformat(AR, '%~wr', [N1]),

maplist(affiche(AL), LP), nl,

maplist(affiche(AC), LP), nl,

maplist(affiche(AR), LP), nl.

affiche(F, L) :-

maplist(my_writef(F), L),

nl.

my_writef(_F, [13]) :-

nl.

my_writef(F, W) :-

writef(F, [W]).

parse([], Max, Max) --> [].

parse(T, N, Max) -->

{ parse_line(T, 0, N1, T1, L, []),

( N1 > N -> N2 = N1; N2 = N)},

[L],

parse(T1, N2, Max).

parse_line([], NF, NF, []) --> [].

parse_line([H|TF], NF, NF, TF) -->

{code_type(H, end_of_line), !},

[].

parse_line(T, N, NF, TF) -->

{ parse_word(T, 0, N1, T1, W, []),

( N1 > N -> N2 = N1; N2 = N)},

[W],

parse_line(T1, N2, NF, TF).

% 36 is the code of '$'

parse_word([36|T], N, N, T) -->

{!},

[].

parse_word([H|T], N, N, [H|T]) -->

{code_type(H, end_of_line), !},

[].

parse_word([], N, N, []) --> [].

parse_word([H|T], N1, NF, TF) -->

[H],

{N2 is N1 + 1},

parse_word(T, N2, NF, TF).

</lang>

Output :

<lang Prolog> ?- aligner.

'Given' a text file of many 'lines,' where fields within a line

are delineated by a single '''dollar''' 'character,' write a program

that aligns each column of fields by ensuring that words in each

column are separated by at least one 'space.'

'Further,' allow for each word in a column to be either left

'justified,' right 'justified,' or center justified within its 'column.'

'Given' a text file of many 'lines,' where fields within a line

are delineated by a single '''dollar''' 'character,' write a program

that aligns each column of fields by ensuring that words in each

column are separated by at least one 'space.'

'Further,' allow for each word in a column to be either left

'justified,' right 'justified,' or center justified within its 'column.'

'Given' a text file of many 'lines,' where fields within a line

are delineated by a single '''dollar''' 'character,' write a program

that aligns each column of fields by ensuring that words in each

column are separated by at least one 'space.'

'Further,' allow for each word in a column to be either left

'justified,' right 'justified,' or center justified within its 'column.'

</lang>