# Matrix A x Matrix B // can't make it work

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 04/12/2008 at 15:10, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   R11
Platform:   Windows  ;
Language(s) :   C.O.F.F.E.E  ;   XPRESSO  ;

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Hello ,
first I have to say I'm really newbie in COFFEE .
What I would like to do is to convert a mirror expresso function in COFFEE .
but I'm facing some troubles when I want to multiply 2 matrix ( A*B ) .
here a basic expresso example I'm trying to convert :
a 'CubeR' object , a 'NulObject' , and a 'CubeL' one. I want to multiply the first 2 matrix ones , to give the CubeL matrix. (one matrix is inverted ) so here the "converted to coffee code" .. but you can see that I'm getting an error in the multiply function ( I've tested several different ways to make it .. each time the same error result ) so my question is , how would you write the "simple" matrix multiplication in coffee please ?  ( pay attention that one of those matrix is inverted ..and the order is important too .. i mean mA*mB isn't the same as mB*mA )
the SDK give 3 solutions : ->GetMulM(m)  or ->MulM_R(m)  or MulM_L(m)   , but no examples are provided.
thanks by advance if anyone can help me ++ clement

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 04/12/2008 at 20:30, xxxxxxxx wrote:

Because MulM_L() and MulM_R() return bool not Matrix! The result of the multiplication is stored back into the Matrix calling the function:

var mat;
mat->MulM_L(mat2);
// mat now has the result (mat2*mat)!

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 05/12/2008 at 01:42, xxxxxxxx wrote:

Hi Robert ,
thank you for the explanation clement