Eval in VEX?

[Trancor]

Hey guys, I searched around for this and can't seem to find a solution, maybe you guys know.

To simplify what I'm doing (its quite more complicated than this, but, ya know), lets just say I have this set up-
string A = "91+";
string B = @ptnum;
string C = A+B;
C == "91+1",  "91+2",  "91+3" . . .

Is there an eval I can do in VEX to get a result like this per point?
91
92
93
94
95

I've tried doing things like -
float( C ) == errors out
or
atof( C )  == "91"

But it doesn't seem to work for me.

Is there any sort of - eval( C )
Or another way to evaluate the string variables as an expression/math?
I'm considering just adding new parameters to evalutate the math through python and to read the parameters into the vex, but is there an easier way to do this?

Edited July 22, 2015 by Trancor

[3iart]

I'm completely guessing, but could this work

string A = "91";
string B = @ptnum;
string C = ftoa(atof(A)+atof(;

having the operator "+" in the string is a bit of a problem I think.

Edited July 21, 2015 by 3iart

[pezetko]

// preview of attributes
string A = "90";
string B = sprintf("%d",i@ptnum);

// atof() converts string to float, sprintf print sum of i@ptnum and A to string @C
s@C = sprintf("%d",i@ptnum+atof(A));

Cheers,

Petr

[Trancor]

Hey guys, thanks for the replies.
The problem is, I can't remove the +
Its goin to be "90+"  or "sin($F)+"  or some variant with the operators built into the string being passed.

Thats why I was hoping for an eval command to process the string like a math problem.

eval("91+5*"+@ptnum);

Type of thing.
atof( )  only grabs the first number in the string it finds, as it appears.
 

Edited July 22, 2015 by Trancor

[fathom]

how is the string being generated?

[Trancor]

User input basically.
It'll find a string like "40*5+@ptnum" and I'm just looking to get the value of that math in VEX.

To mimic eval( )  from any number of other scripting and programming langues.

Edited July 22, 2015 by Trancor

[fathom]

can you use snippets?

 

check out some of the pop nodes like wind.  they have user entered vex code as part of their functionality.

[Trancor]

Not in this case, I sort of gave up and just added a VEXpression parameter, I guess similar to snippets, but to set point attributes for the code I'm writing to read from.
Annoying, but works.

[MrScienceOfficer]

You would need to write a parser to make it work with a string input.

 

Probably have to use the HDK to extend VEX for something like that.   

[Guest mantragora]

Maybe this is your answer: 

1. http://www.sidefx.com/docs/houdini14.0/hom/pythonsop

2. http://www.sidefx.com/docs/houdini14.0/hom/hou/runVex

3. http://stackoverflow.com/questions/9383740/what-does-pythons-eval-do

?

Edited July 23, 2015 by fântastîque Mântragorîè

[anim]

you can as well insert content of user input parameter into your vex code

 

some vex code `chs("../userinputparm")` more vex code;

 

it will get expanded before compilation, then it will evaluate as a vex code

it won't work however for animated parms as it get's expanded only on the first frame

[Trancor]

Thanks everyone.
Captain, I think that might be the solution here.  Not a fan though, hahah.
Since its all VEX, parsing out the string in python and applying any particle numbers seems futile to me.
 

I got around it with just opening up a VEXpression input on my otl, changes workflow a little, but at least it works.

 

I just figured, every languages I've ever used had an eval command, was sort of hoping VEX had

Edited July 24, 2015 by Trancor