Empty strings in if statements

[paues]

I have come across a rather counter-intuitive behavior in EViews. I presumed (and believe that most users would do the same) that this code

Code: Select all

if %name<>"Fredrik" then
@uiprompt("%name is NOT Fredrik")
else
@uiprompt("%name is Fredrik")
endif

if %name="Fredrik" then
@uiprompt("%name is Fredrik")
else
@uiprompt("%name is NOT Fredrik")
endif

would result in the two dialog boxes both reading "%name is NOT Fredrik". No value has been assigned to the string variable %name, which means it is equal to "", which in turn is not equal to "Fredrik".

However, both of if statements return false and the first dialog box thus reads "%name is Fredrik". In order for the first if statement to return true, in line with my intuition, it needs to be rewritten as

Code: Select all

if @isempty(%name) or %name<>"Fredrik" then
@uiprompt("%name is NOT Fredrik")
else
@uiprompt("%name is Fredrik")
endif

[EViews Gareth]

As outlined in the manual, you should use @eqna to test for equality of strings, not "=" or "<>".

[paues]

I missed that. Thank you!