False

From the SETL Wiki

false is the name of the predefined boolean constant that represents logical falsehood in SETL (like most high-level languages.)

Operations involving false include:

• Use it as the condition in an if statement:

  if false then
    print('You should not see this');
  else
    print('You should see this');
  end;
  

  
  

• Use it as the condition in an while statement:

  (while false)
    print('You should not see this');
  end while;
  
  (until false)
    print('You should see this repeated infinitely');
  end until;
  

  repeat ... until false

• Convert it to a string:

  str false
  

  Result: '#F'

• Parse it from a string:

  unstr '#F'
  

  Result:false

• Query its type:

  print(type false, is_boolean false, is_integer false, denotype '#F');
  

  Output:BOOLEAN #T #F BOOLEAN

• Insert it into a set or map:

  s := {false};
  false in s;
  true in s;
  
  not_map := {[true, false], [false, true]};
  not_map(false);
  not_map(true);
  

  Results:
  #T
#F

#T
#F