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


with Ada.Text_IO; use Ada.Text_IO;
with Ada.Strings.Maps; use Ada.Strings.Maps;
with Ada.Characters.Handling; use Ada.Characters.Handling;
procedure pangram is
 
   function ispangram(txt: String) return Boolean is
     (Is_Subset(To_Set(Span => ('a','z')), To_Set(To_Lower(txt))));
 
begin
   put_line(Boolean'Image(ispangram("This is a test")));
   put_line(Boolean'Image(ispangram("The quick brown fox jumps over the lazy dog")));
   put_line(Boolean'Image(ispangram("NOPQRSTUVWXYZ  abcdefghijklm")));
   put_line(Boolean'Image(ispangram("abcdefghijklopqrstuvwxyz"))); --Missing m, n
end pangram;
 