Pangram checker

You are encouraged to solve this task according to the task description, using any language you may know.
A pangram is a sentence that contains all the letters of the English alphabet at least once.

For example:   The quick brown fox jumps over the lazy dog.



Task

Write a function or method to check a sentence to see if it is a   pangram   (or not)   and show its use.



Related tasks

   determine if a string has all the same characters
   determine if a string has all unique characters


Sequence isPangram := method(
    letters := " " repeated(26)
    ia := "a" at(0)
    foreach(ichar,
        if(ichar isLetter,
            letters atPut((ichar asLowercase) - ia, ichar)
        )
    )
    letters contains(" " at(0)) not     // true only if no " " in letters
)
 
"The quick brown fox jumps over the lazy dog." isPangram println    // --> true
"The quick brown fox jumped over the lazy dog." isPangram println   // --> false
"ABC.D.E.FGHI*J/KL-M+NO*PQ R\nSTUVWXYZ" isPangram println           // --> true