Hello,

i assume you're currently passing the array in a character variable and DECLAREing the array parameter as STRING type, maybe your DoubleArrayToString routine has some faults?

you may have a look at download #28338, it contains a class called "CDoubleArray" in the file "vfp2c.prg" which is a wrapper around a real C style array of doubles

you may use it like:

&& init library as described in help ..
LOCAL ArrayWithYourValues[20], loCArray, lnParm1, lnParm2
&& init ArrayWithYourValues from somewhere ...
loCArray = CREATEOBJECT('CDoubleArray')
loCArray.MarshalArray(@ArrayWithYourValues)
&& now loCArray has created a copy of your array as an C style array
&& you can pass to your DLL function
DECLARE INTEGER foo IN foo.dll DOUBLE @ someParm1, DOUBLE @ someParm2, INTEGER theArray

lnParm1 = 0.0
lnParm2 = 0.0
?Foo(@lnParm1,@lnParm2,loCArray.Address)
&& loCArray.Address contains the real memory address of the C style array ..

that's the only thing that currently comes to my mind ... since your question was somewhat "generic" in nature ..

Regards
Christian