If statement

Dear all,

How can make an if statement in grasshopper, for example.

If input values is x then,

x = 1 then y = 332

x = 2 then y = 32

x = 3 then y = 4423

where input x and output y has no mathematical relations.

Thanks in advance.

Replies to This Discussion

Permalink Reply by Sylvain Usai on July 17, 2013 at 2:53pm

If y is just a list of predeterminated values :

you could create a non multiline panel filled with your value...

X is now the index of your list,

y is the item,

Use a list item to find y according to x.

Permalink Reply by ryr on July 17, 2013 at 3:21pm

sound a good idea. however my index is not sequential.

Permalink Reply by David Rutten on July 17, 2013 at 3:38pm

Key Value search using Sylvains logic should work.

If you really want to create an If statement using code, then it would look like this:

If(x=1, 332, If(x=2, 32, If(x=3, 4423)))

Which is pretty horrific.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by ryr on July 18, 2013 at 2:25am

Thanks David,

Can this be created using grasshopper components?

Permalink Reply by David Rutten on July 18, 2013 at 4:06am

Sure. Both methods in the attached file.

David Rutten

david@mcneel.com

Tirol, Austria

Attachments:

KeyValueSearch.gh, 9 KB

Permalink Reply by Sylvain Usai on July 18, 2013 at 4:13am

Awesome !!! Is there an index of all the command you can use in formulas ?

Permalink Reply by David Rutten on July 18, 2013 at 4:47am

f:N->R button in the upper right of the expression editor.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Sylvain Usai on July 18, 2013 at 5:46am

Ok, so in that case, you use the B as an else ?

Permalink Reply by David Rutten on July 18, 2013 at 5:55am

The Grasshopper expression language doesn't support multiple lines of proper conditional statements. This is something I'd like to improve for GH2, probably build the entire language on VB.NET with some special features to maintain backwards compatibility.

Basically an If statement is an If function. It requires three parts, a condition, a result for TRUE and a result for FALSE. So this VB statement:

If (x) then

A

Else

B

End If

Would be written as:

If (x, A, B)

In the GH expression language.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Ivan Hawk on May 4, 2016 at 12:33pm

Hi dear David

would you please indicate me a good source where to study the correct syntax for GH expression language ?

thanks in advance

regards

Ivan - Veneto IT

Permalink Reply by David Rutten on May 4, 2016 at 1:22pm

No such thing exists I'm afraid. But it's basically a VBScript syntax with a bunch of additional methods (click on the f(x)->R button in the top right of the Expression editor to see them all).

Since conditionals in VBScript typically require more than one line, there's an additional function called If() which takes three arguments, the first one must evaluate to a boolean, the second argument will be returned if the first argument is true and the third argument will be returned if the first argument is false.

The post you're responding to is very old btw. Expressions in GH2 are already operational and they can be full VB.NET or C# methods, and support for python will at some point be added as well.

Permalink Reply by Ivan Hawk on May 5, 2016 at 2:26pm

Many thanks for the helpful answer David.

The f(x)->R gave me a clear view of the available commands, clear also the reason for the if() function syntax

David , congratulation once again for the incredible instrument you have created . GH is fantastic !!!

kindest regards

Ivan - Veneto IT