topic Re: SET EVALUATE in QlikView

SET EVALUATE

pradeep92 — Wed, 25 Nov 2020 16:16:04 GMT

hi,

I have specified Set x=3+4; in script and when i evaluate as =$(x) in text box, it gives 7.Why is that so ?

Re: SET EVALUATE

Clever_Anjos — Mon, 06 Nov 2017 10:08:24 GMT

It seems to be correct to me, what do you see as wrong?

What do you expect to see?

Re: SET EVALUATE

prma7799 — Mon, 06 Nov 2017 10:13:47 GMT

What is your required output?

Re: SET EVALUATE

Anil_Babu_Samineni — Mon, 06 Nov 2017 10:47:43 GMT

Off course, Because you are computing using $() indicator. Remove that and check with simple x ??

Set x=3+4; //vVar has the expression 2+3 as value we have to compute it using $(vVar) which returns 5

Let x=3+4; //vVar has the computed value 5

Re: SET EVALUATE

Peter_Cammaert — Mon, 06 Nov 2017 10:50:39 GMT

The different engines involved act like that because of two simple reasons:

text literal assignment (scripting engine), and
text substitution (expression evaluator)

A SET statement assigns the right hand part as-is to the variable specified in the left hand part. So x will contain string '3+4'.

Now in the expression, the evaluator will perform $-sign substitution first, before doing anything else. That gets the original expression =$(x) converted into =3+4 after which the expression is finally evaluated and produces a fixed value of 7. That one gets displayed.

Note that what applies to the expression with respect to $-sign substitution always coming first, also applies to the right-hand part of the SET statement. $-sign substitution in the right-hand part of a SET statement will be applied even before the scripting engine tries to figure out what statement it is looking at. And that's the main reason why stuff like the following even works at all !

SET y = SET;

$(y) x = 3+4;

If this explanation is unclear, please ask away.

Best,

Peter