Check whether letters of word are in alphabetical order Write a function/program that accepts a string of lower/uppercase letters [A-Za-z] as input, that checks whether the occuring letters are unique and in alphabetical order (ignoring lower and uppercase) or not. The output must be truthy if they are unique and in alphabetical order and falsy if not.

Here some testcases

a                           true
abcdefGHIjklmnopqrSTUVWXyz  true     
aa                          false
puz                         true
puzz                        false
puzZ                        false
puZ                         true
PuZ                         true
pzu                         false
pzU                         false
abcdABCD                    false
dcba                        false


If you want, run your program on all words of a wordlist like this one and and post some interesting ones =).

Score

Lowest number of bytes wins.
CJam, 8 bytes

lel_$_&amp;=


Here is a test harness for all examples in the challenge. This returns 0 or 1 (which are falsy and truthy, respectively, in CJam).

And here is a script to filter the word list in the question (takes a few seconds to run). You'll have to copy the word list into the input field manually, because it's too long for a permalink.

Explanation

l        "Read input.";
 el      "Convert to lower case.";
   _$    "Get a copy and sort it.";
     _&amp;  "Remove duplicates (by computing the set intersection with itself).";
       = "Check for equality with original (lower case) word.";