fpdevil · March 6, 2017 18:59
diff --git a/palindrome.erl b/palindrome.erl
 %%%-----------------------------------------------------------------------------
 %%% @author Sampath Singamsetty <>
 %%% @copyright (C) 2017, Sampath Singamsetty
 %%% @doc Check if a string or sentence is a palindrome.
 %%% Define a function palindrome, that returns true or false depending on
 %%% whether the list is a palindrome - the same when read right to left
 %%% as when read left to right.
 %%% @end
 %%% Created : 06 Mar 2017 by Sampath Singamsetty <>
 %%%-----------------------------------------------------------------------------
 -module(palindrome).
 -include_lib("eunit/include/eunit.hrl").
 -export([palindrome/1]).

 %% palindrome of string or sentence
 %% for the string or the sentence, we will first strip all the below characters
 %% "\t !\"',.:;?[\\]^_`" which is the ascii list [9,32,33,34,39,44,46,58,59,63,91,92,93,94,95,96]
 palindrome([]) ->
    true;
 palindrome([_]) ->
    true;
 palindrome(X) ->
    %% filtering out the unneeded characters from string
    C = lists:filter(fun(Str) -> not(lists:member(Str,[9,32,33,34,39,44,46,58,59,63,91,92,93,94,95,96])) end, X),
    %% convert the filtered string to all lower case
    palindrome_str(string:to_lower(C)).

 %% helper function which does the actual palindrome check
 palindrome_str([X|Xs]) ->
    Rest = trimmed(Xs),
    (X =:= hd(lists:reverse(Xs))) and palindrome(Rest).

 %% helper function for getting the string between first and last values
 trimmed(Xs) ->
    lists:reverse(tl(lists:reverse(Xs))).

 palindrome_test_() ->
    [?_assertEqual(true, palindrome("Madam I\'m Adam")),
     ?_assertEqual(true, palindrome("A man, a plan, a canal, Panama!")),
     ?_assertEqual(true, palindrome("abc 1 cba")),
     ?_assertEqual(true, palindrome("Salisbury moor, sir, is roomy. Rub Silas.")),
     ?_assertEqual(true, palindrome("No, it is opposed; Art sees Trade's opposition.")),
     ?_assertException(error, function_clause, palindrome(123))
    ].

 %% 1> eunit:test(palindrome,[verbose]).
 %% ======================== EUnit ========================
 %% module 'palindrome'
 %%   palindrome:38: palindrome_test_...ok
 %%   palindrome:39: palindrome_test_...ok
 %%   palindrome:40: palindrome_test_...ok
 %%   palindrome:41: palindrome_test_...ok
 %%   palindrome:42: palindrome_test_...ok
 %%   palindrome:43: palindrome_test_...ok
 %%   [done in 0.018 s]
 %% =======================================================
 %%   All 6 tests passed.
 %% ok
	%%%-----------------------------------------------------------------------------
	%%% @author Sampath Singamsetty <>
	%%% @copyright (C) 2017, Sampath Singamsetty
	%%% @doc Check if a string or sentence is a palindrome.
	%%% Define a function palindrome, that returns true or false depending on
	%%% whether the list is a palindrome - the same when read right to left
	%%% as when read left to right.
	%%% @end
	%%% Created : 06 Mar 2017 by Sampath Singamsetty <>
	%%%-----------------------------------------------------------------------------
	-module(palindrome).
	-include_lib("eunit/include/eunit.hrl").
	-export([palindrome/1]).

	%% palindrome of string or sentence
	%% for the string or the sentence, we will first strip all the below characters
	%% "\t !\"',.:;?[\\]^_`" which is the ascii list [9,32,33,34,39,44,46,58,59,63,91,92,93,94,95,96]
	palindrome([]) ->
	true;
	palindrome([_]) ->
	true;
	palindrome(X) ->
	%% filtering out the unneeded characters from string
	C = lists:filter(fun(Str) -> not(lists:member(Str,[9,32,33,34,39,44,46,58,59,63,91,92,93,94,95,96])) end, X),
	%% convert the filtered string to all lower case
	palindrome_str(string:to_lower(C)).

	%% helper function which does the actual palindrome check
	palindrome_str([X\|Xs]) ->
	Rest = trimmed(Xs),
	(X =:= hd(lists:reverse(Xs))) and palindrome(Rest).

	%% helper function for getting the string between first and last values
	trimmed(Xs) ->
	lists:reverse(tl(lists:reverse(Xs))).

	palindrome_test_() ->
	[?_assertEqual(true, palindrome("Madam I\'m Adam")),
	?_assertEqual(true, palindrome("A man, a plan, a canal, Panama!")),
	?_assertEqual(true, palindrome("abc 1 cba")),
	?_assertEqual(true, palindrome("Salisbury moor, sir, is roomy. Rub Silas.")),
	?_assertEqual(true, palindrome("No, it is opposed; Art sees Trade's opposition.")),
	?_assertException(error, function_clause, palindrome(123))
	].

	%% 1> eunit:test(palindrome,[verbose]).
	%% ======================== EUnit ========================
	%% module 'palindrome'
	%% palindrome:38: palindrome_test_...ok
	%% palindrome:39: palindrome_test_...ok
	%% palindrome:40: palindrome_test_...ok
	%% palindrome:41: palindrome_test_...ok
	%% palindrome:42: palindrome_test_...ok
	%% palindrome:43: palindrome_test_...ok
	%% [done in 0.018 s]
	%% =======================================================
	%% All 6 tests passed.
	%% ok