Creating a C# component with already completed C# code?

Hello.

I would like to make a C# component in Rhino, with following C# code:

#include<stdio.h>
#include<math.h>

void main(){
double f0;
double n21,n22,f;
double A=0.373;
printf("# f0, f, n21,n22\n");
for(f0=1.0e-10;f0<=0.1;f0=f0*pow(10.0,0.02)){
n21=-2.0+floor(1.29*pow(f0,-0.25));
n22=-2.0+floor(A*pow(f0,-0.25)*(12.0)*sqrt((n21+2.0)/(11.0*n21+43.0)));
f=(27.0/2.0)*f0*pow(n21+2.0,-2.0)*pow(n22+2.0,-2.0);
printf("%g %g %i %i\n",f0,f,(int)n21,(int)n22);
}
}

Any help with this please?

I am beginner with both C# and creation of C# components in Grasshopper.

I attached the .c file with the same above code.

Thank you.

Attachments:

n2.c, 1 KB

Replies to This Discussion

Permalink Reply by Sridevi Koonath on June 14, 2012 at 1:00am

Hello,

The code below should work when pasted into a C# script component. For now, there is an error because floor is not defined anywhere.

double f0;
double n21, n22, f;

double A = 0.373;

output = "# f0, f, n21, n22 \n";

for (f0 = 1.0e-10; f0 <= 0.1; f0 = f0 * Math.Pow(10.0, 0.02))
{
n21 = -2.0 + floor(1.29 * Math.Pow(f0, -0.25));
n22 = -2.0 + floor(A * Math.Pow(f0, -0.25) * (12.0) * Math.Sqrt((n21 + 2.0) / (11.0 * n21 + 43.0)));
f = (27.0 / 2.0) * f0 * Math.Pow(n21 + 2.0, -2.0) * Math.Pow(n22 + 2.0, -2.0);

output = output + f0.ToString() + " " + f.ToString() + " " + ((int) n21).ToString() + " " + ((int) n22).ToString() + "\n";
}

Permalink Reply by Sridevi Koonath on June 14, 2012 at 2:23am

Hello again!

It seems that the C# script component requires at least one input parameter [1], even if it is not used. So you will have to fix that in the component in my solution above.

[1] Then the RunScript method will look like this:

private void RunScript(object x, ref object output)

{blah...blah}

Permalink Reply by David Rutten on June 14, 2012 at 2:49am

Yeah this is a bug in the current version. The Script components don't like having no inputs or no outputs. I've fixed it for 0.9

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Giulio Piacentino on June 14, 2012 at 4:26am

The code you post is actually C.

In C#, Floor and Pow are methods in the static Math class. I think Sridevi's nice sample should already give a good idea, but please let your voice be heard in case there are any further doubts.

Thanks,

- Giulio
________________
giulio@mcneel.com

Permalink Reply by djordje on June 14, 2012 at 5:07am

Thank you for the replies. All of you.

Sridevi thank you!
But I am not doing something right. Because I am not not getting anything except from <null> in the Panel (String). Take a look:

@ Giulio yes it is C code. Although I do not know the difference between C and C#.

Permalink Reply by David Rutten on June 14, 2012 at 5:36am

You need to assign a value to the 'ref object A' argument in the RunScript method signature. You're declaring another variable called A inside your method 'double A = ...'. I'm not sure how this is legal, I'd expected a compiler error.

Do not declare A again, just assign your outputs directly to the A that already exists.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by David Rutten on June 14, 2012 at 5:46am

C is an old language. It was developed in the early 1970's and it is quite primitive. Bjarne Stroustrup (among others) extended C with the notion of OOP and it became 'C with classes' or 'C plus plus'. C++ arose in the early 80's and it is the language in which Rhino itself is written. C# is the next major version in this language family and it is the one used in .NET development. C# first appeared somewhere around 2001 and has gone through 4 major upgrades since then.

Grasshopper is written in C# and VB.NET (which is the .NET flavour of the Visual Basic language family) and the script components also allow only C# and VB.NET, none of the other c-style or vb-style languages out there.

There is no way to flawlessly convert code from C++ to C#. The two languages have non-overlapping features. Simple mathematical algorithms though tend to be highly portable.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Sridevi Koonath on June 14, 2012 at 5:52am

Hello, a couple of things in addition to what David pointed out:

1. Replace floor with Math.Floor

2. You cannot declare local variables inside the RunScript method with the same names as that of the input parameters (since they becomes the names of the arguments for the RunScript method). This gives an error. So either

Rename the input parameters to x, y, z, etc., OR
Since the actual values of f0, f, n21, n22 are calculated inside the component, there is no need to input any values to them from the outside. So you can delete all the input parameters except f0, and then rename f0 to something else. This is just a dummy parameter to make the component work.

Permalink Reply by djordje on June 14, 2012 at 6:32am

I chose the second solution (to delete all the input parameters, and renamed f0 to t).

Still something is wrong:

Permalink Reply by Sridevi Koonath on June 14, 2012 at 6:39am

1. You forgot to replace floor with Math.Floor inside the code.

2. In my example, I had set my output parameter name as output (see above, it says ref object output). But since you have renamed the output parameter to r, wherever it says output in the code, replace it with r.

Permalink Reply by djordje on June 14, 2012 at 6:49am

Thank you Sridevi! It works!
Sorry for being lazy.

One more question, if I may ask: is there a way for this script to show the results (output = "# f0, f, n21, n22 \n";) by indexes (indices)?

Permalink Reply by Sridevi Koonath on June 14, 2012 at 7:03am

Ah, so that is why there was a # symbol in the heading :)
Assuming that you want the numbering to start from 1, add/edit the following lines:

int index;

for (f0 = 1.0e-10, index = 1; f0 <= 0.1; f0 = f0 * Math.Pow(10.0, 0.02), index++)

output = output + index.ToString() + " " + f0.ToString() + " " + f.ToString() + " " + ((int) n21).ToString() + " " + ((int) n22).ToString() + "\n";