DEFINEDP name DEFINED? name
name
Outputs TRUE if the input is the name of a user-defined procedure or a library procedure.
name must be a word.
SHOW DEFINEDP "forward false
SHOW DEFINEDP "forward
DEFINE "ABC [[a b] [PRINT :a] [PRINT :b]] SHOW DEFINEDP "ABC true
DEFINE "ABC [[a b] [PRINT :a] [PRINT :b]] SHOW DEFINEDP "ABC