Expression editor problem

Replies to This Discussion

Permalink Reply by Chris Tietjen on January 27, 2011 at 5:15pm

Permalink Reply by JORGE LUIS TREVIÑO GARZA on January 27, 2011 at 6:13pm

thanks! very useful!

Permalink Reply by David Rutten on January 28, 2011 at 6:50am

The reason your original expression fails is because the comparison operators are not handled at the same time.

 

5 < x ≤ 10

 

First it will compare 5 to x and if 5 is smaller the result will be True, otherwise the result will be False. So now we have two possible remaining expressions:

 

True ≤ 10

False ≤ 10

 

True and False cannot be compared to Integers (actually they probably should, False equals 0 and True equals 1, but if won't solve your problem).

 

You are performing two separate comparisons, which you'll need to write as two separate operations, combining them with a Boolean operator, like so:

 

(x >= 6) And (x <= 10)

 

Which results in the following possibilities:

 

x smaller than 6    ->    (False) And (True)

x larger than 10    ->    (True) And (False)

otherwise            ->     (True) And (True)

 

For And to return True, both the left and the right-hand value must be True, thus the first two possibilities both return False.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Juan Alberto Galicia Osorno on January 28, 2011 at 8:17am

:0 oh thanks for explaining that :D

 

 

Permalink Reply by JORGE LUIS TREVIÑO GARZA on February 13, 2011 at 3:35pm

Thanks for explaining!! I think I understand better now!

Permalink Reply by Scott McMillen on August 18, 2012 at 1:31pm

Hey how do you set your Single Variable Functions to show what you wrote in the function without going into the expression editor?

This is really helpful.  I just spent an hour trying to do this by making a quadratic function that only goes below 0 at the range of x values I needed (and ended up with the same problem)

Permalink Reply by djordje on August 18, 2012 at 6:30pm

You have to set it up Scott - set up the function by going into the expression designer (editor).

Either that or you can simply write the same thing you typed into expression designer to a Panel, and then connect the panel to the "F" input plug of the "function1" component:

(I typed "x*3" in the expression designer of the first "function1" component)

What Chris did is, he renamed the "F" input of the "function1" component to something else. In this case "x>5, x<10, x=10". You can rename it by yourself by right clicking on that "F" input.

But that does not affect the function. He did that to clarify better what did he write into the expression designer.

I hope I did not make a mistake on this?

It seems it is maybe a time for me to stop playing like somebody that knows some basics of GH.

Permalink Reply by Chris Tietjen on August 20, 2012 at 1:37am

You got it.  Good explanation.

Chris

Permalink Reply by Scott McMillen on August 30, 2012 at 11:58am

Okay, thank you.

I have seen that done a lot on this site and thought it may be some setting in grasshopper I didn't know about.  I need to make a presentation based around my grasshopper definition and this seems like the best way of presenting the definition to someone.

Permalink Reply by Joe Burleigh on September 27, 2018 at 8:01pm

Hello I am getting a simular issue where my expression is  recievening a syntax error no matter how I write it. Anyone know of a solution?

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