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Letter frequency: Difference between revisions
→{{header|Python}}
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Output:
<pre>-> (("^J" . 2) ("a" . 1) ("b" . 1) ("c" . 2) ("d" . 2) ("e" . 1) ("f" . 1))</pre>
=={{header|Prolog}}==
Works with SWI-Prolog. <br>
Only alphabetic codes are computed in uppercase state. <br>
Uses '''packlist/2''' defined there : http://rosettacode.org/wiki/Run-length_encoding#Prolog <br>
<lang Prolog>frequency(File) :-
read_file_to_codes(File, Code, []),
% we only keep alphabetic codes
include(my_code_type, Code, LstCharCode),
% we translate char_codes into uppercase atoms.
maplist(my_upcase, LstCharCode, LstChar),
% sort and pack the list
msort(LstChar, SortLstChar),
packList(SortLstChar, Freq),
maplist(my_write, Freq).
my_write([Num, Atom]) :-
swritef(A, '%3r', [Num]),
writef('Number of %w :%w\n', [Atom, A]).
my_code_type(Code) :-
code_type(Code, alpha).
my_upcase(CharCode, UpChar) :-
char_code(Atom, CharCode),
upcase_atom(Atom, UpChar).
:- use_module(library(clpfd)).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% ?- packList([a,a,a,b,c,c,c,d,d,e], L).
% L = [[3,a],[1,b],[3,c],[2,d],[1,e]] .
%
% ?- packList(R, [[3,a],[1,b],[3,c],[2,d],[1,e]]).
% R = [a,a,a,b,c,c,c,d,d,e] .
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
packList([],[]).
packList([X],[[1,X]]) :-
!.
packList([X|Rest],[XRun|Packed]):-
run(X,Rest, XRun,RRest),
packList(RRest,Packed).
run(Var,[],[1,Var],[]).
run(Var,[Var|LRest],[N1, Var],RRest):-
N #> 0,
N1 #= N + 1,
run(Var,LRest,[N, Var],RRest).
run(Var,[Other|RRest], [1,Var],[Other|RRest]):-
dif(Var,Other).
</lang>
Output for this file
<pre>Number of A : 63
Number of B : 7
Number of C : 53
Number of D : 29
Number of E : 65
...
Number of T : 52
Number of U : 20
Number of V : 10
Number of W : 8
Number of X : 6
Number of Y : 12
true .
</pre>
=={{header|Python}}==
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