stc1.erl

-module(stc1).
-compile(export_all).

%% copy -- copy input to output
%%
%% We're not defining primitives like in the book,
%% We can't detect ENDFILE with io:get_line/1, and
%% it already receive only one line so no need to
%% detect ASCII NEWLINE as well.
%%
%% Since we can't detect ENDFILE, we can mimic ed(1)
%% behavior so that a "." in an empty line will quit.
%%
%% Correction: we can't detect ENDFILE in Erlang Shell,
%% but when running from terminal as an escript program,
%% you can pattern match Ctrl-D as eof.
copy() ->
    Input = ststd:getc(),
    copy(Input).

copy(eof) ->
    {ok, eof};
copy(".\n") ->
    {ok, eof};
copy(Input) ->
    ststd:putc(Input),
    copy().

%% charcount -- count characters in standard input
charcount() ->
    Input = ststd:getf(),
    charcount(Input, 0).

charcount(eof, Acc) ->
    ststd:putf("~w~n", [Acc]);
charcount([], Acc) ->
    charcount(eof, Acc);
charcount([_|T], Acc) ->
    charcount(T, Acc + 1).

%% linecount -- count lines in standard input
%%
%% Since Erlang "String" is an array of numbers,
%% We can detect "\n" as ASCII 10.
linecount() ->
    Input = ststd:getf(),
    linecount(Input, 0).

linecount(eof, Acc) ->
    ststd:putf("~w~n", [Acc]);
linecount([], Acc) ->
    linecount(eof, Acc);
linecount([10|T], Acc) ->
    linecount(T, Acc + 1);
linecount([_|T], Acc) ->
    linecount(T, Acc).

%% wordcount -- count words in standard input
%%
%% ASCII Blank = 32, Newline = 10, Tab = 9.
%%
%% BUGS
%% If Ctrl-D during a word, will not count such a word.
wordcount() ->
    Input = ststd:getf(),
    wordcount(Input, false, 0).

wordcount(eof, Acc) ->
    ststd:putf("~w~n", [Acc]).

wordcount([], _, Acc) ->
    wordcount(eof, Acc);
wordcount([H|T], inword, Acc) ->
    case lists:member(H, [9, 10, 32]) of
        true -> wordcount(T, false, Acc + 1);
        false -> wordcount(T, inword, Acc)
    end;
wordcount([H|T], _, Acc) ->
    case lists:member(H, [9, 10, 32]) of
        true -> wordcount(T, false, Acc);
        false -> wordcount(T, inword, Acc)
    end.

%% putwc -- special output for wc
%%
%% BUGS
%% It doesn't print the name of the file as of yet.
putwc(ArgList) ->
    ststd:putf(" ~w ~w ~w~n", ArgList).

%% wc -- count words, lines and characters
%%
%% BUGS
%% If Ctrl-D during a word, will not count word or curent line.
wc() ->
    Input = ststd:getf(),
    wc(Input, false, 0, 0, 0).

wc([], _, WC, LC, CC) ->
    putwc([LC, WC, CC]);
wc([H|T], inword, WC, LC, CC) ->
    case lists:member(H, [9, 10, 32]) of
        true when H =:= 10 -> wc(T, false, WC+1, LC+1, CC+1);
        true -> wc(T, false, WC+1, LC, CC+1);
        false -> wc(T, inword, WC, LC, CC+1)
    end;
wc([H|T], _, WC, LC, CC) ->
    case lists:member(H, [9, 10, 32]) of
        true when H =:= 10 -> wc(T, false, WC, LC+1, CC+1);
        true -> wc(T, false, WC, LC, CC+1);
        false -> wc(T, inword, WC, LC, CC+1)
    end.

%% settabs -- set initial tab stops
%%
%% We can't generate a list/array because we don't have a MAXLINE.
%% settabs returns the TabSpace value instead.
settabs() ->
    TabSpace = 4,
    TabSpace.

%% tabpos -- return true if col is a tab stop
%%
%% Doesn't make sense in using MAXLINE since Erlang handle
%% the EOF and buffer size for us, unless we're using
%% io:get_chars/2 because the second parameter of the said
%% function is exactly a limiter.
tabpos(Col) ->
    TabSpace = settabs(),
    TabSpace - Col rem TabSpace.

%% detab - convert tabs to blanks
%%
%% It doesn't work exactely as the Pascal version.
%% See settabs/0 and tappos/1 for details.
%%
%% BUGS
%% Special characters other than 9, 10, 32 might transform
%% the return string in numbers and screw everything.
detab() ->
    Input = ststd:getf(),
    detab(Input, 0, []).

detab([], _, Acc) ->
    ststd:putf("~p~n", [Acc]);
detab([9|T], Col, Acc) ->
    Feed = tabpos(Col),
    Blanks = lists:map(fun(_) -> 32 end, lists:seq(1, Feed)),
    detab(T, Col+Feed, lists:concat([Acc, Blanks]));
detab([H|T], Col, Acc) ->
    detab(T, Col+1, lists:concat([Acc, [H]])).