OpenEuphoria

Re: Testing for NULL

• Posted by andi49 Sep 02, 2015
• 1940 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}) 

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

Hi, i'am not really sure about what you are like todo.

But what about this? (Windows code)

-- #!/usr/bin/env eui  
include std/console.e -- for anykey() 
  
object x = 0 
-- x="test" 
-- 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  
if atom(x) then 
	printf(1, "x is %d\n", {x}) -- How to test for this error? 
else 
	printf(1, "x is %s\n", {x}) -- How to test for this error? 
end if 
  
-- 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})  
if atom(x) then 
	printf(1, "x is %d\n", {x}) -- How to test for this error? 
else 
	printf(1, "x is %s\n", {x}) -- How to test for this error? 
end if 
any_key()