A pangram is a sentence that uses all the letters in the alphabet.

This is one way to determine if a sentence is a pangram using RETRO.

First, define a string containing the alphabet:

~~~'abcdefghijklmnopqrstuvwxyz 'FULL s:const ~~~

Then a blank string of the same length for the test data:

~~~'__________________________ 'TEST s:const ~~~

Now a word to do the actual test.

~~~:s:pangram? (s-f)   '__________________________ &TEST #26 copy   s:to-lower [ c:letter? ] s:filter   [ dup $a - &TEST + store ] s:for-each   &TEST &FULL s:eq? ; ~~~

Breaking this down, the first line:

' &TEST #26 copy

Copies a blank string over the TEST string. Then:

s:to-lower [ c:letter? ] s:filter

Converts the string to lowercase and strips out anything that's not a letter. Then a quick iteration over each character:

[ dup $a - &TEST + store ] s:for-each

Reduces the letter to an index into the TEST string and stores the letter at the appropriate spot. And finally:

&TEST &FULL s:eq? ;

Just compares the TEST and FULL strings to get the result.

Here's a couple of test cases:

~~~'Hello_world! s:pangram? 'The_quick_brown_fox_jumped_over_the_lazy_dogs. s:pangram? ~~~