OpenEuphoria

Testing for NULL

• Posted by xecronix Sep 02, 2015
• 2011 views

#!/usr/bin/env eui 
 
sequence x 
-- The next executable line is an error as expected.   
-- But, how can I test/defend against this error in advance? 
-- ie 
-- 
-- if x = ??? then 
--   -- do something 
-- end if 
printf(1, "x is %s", {x}) -- How to test for this error? 
 
-- No problem here.  Works as I expected 
x = "some sequence" 
printf(1, "x is %s\n", {x}) 
 
-- I don't know how to express this in Euphoria either. 
-- What I hoped for was a way to set x to some value  
-- after valid assignment that would cause the error at the  
-- start of the code. 
x = 0 -- This causes a type error.  But how do you unset a variable? 
printf(1, "x is %s\n", {x}) 

This came up when I wanted to do this

public function fname(sequence self, sequence x = 0) 
    if x then 
        self[FNAME] = x 
    end if 
    return self[FNAME] 
end function