[mg14738] Re: Simple MathLink question
Kevin Leuthold
What I stated below is only partly correct. In particular, the
following paragraph is correct.
>The first is that MathLink encodes its data in a private manner. This
>wouldn't be a problem if you were calling MLPutString with
>alphanumeric characters, since these characters are represented
>literally. But it does mean that calling MLPutString on a string with
>backslashes in it won't work. This is discussed in the MathLink
>Developer Guide, in the "What's New" section, in a subsection entitled
>"The Biggest Compatibility Issue". Instead of MLPutString in this
>situation, consider using MLPutByteString.
However, the rest of the post is inaccurate.
If you are sending Get["D:\\new.txt"] to Mathematica, using
MLPutFunction and MLPutByteString, then the string will only be parsed
once - by your compiler. Mathematica's parser will not see this
string since you are building it up yourself. So despite my original
post, the following is correct:
MLPutFunction( stdlink, "Get", 1);
MLPutByteString( stdlink, "D:\\new.txt", 10);
There are situations where a string would be parsed by both your C
compiler and Mathematica, and so 4 backslashes would be needed for
each pathname separator. Here is an example:
MLPutFunction( stdlink, "ToExpression", 1); MLPutByteString( stdlink,
"Get[\"D:\\\\new.txt\"]", 18);
Sorry for any confusion.
Kevin Leuthold
MathLink Group
Wolfram Research
>Jim McGuire <ji...@opticalres.com> writes:
>>I am trying to read in a set of Mathematica definitions which was saved
>>using DumpSave["MathLink_USER.mx",{function1,function2,...}] from
>>D:\jimm\svgcn018 directory on my NT PC. I have been unsuccessful
>>reading it into the MathLink session. The definitions are very long
>>and I do not relish the thought of importing them using MLPut commands.
>>I tried the following test to see if the link is open. It shows the
>>proper data is ready to be read by the link
>>MLPutFunction(stdlink,"EvaluatePacket",1);
>> MLPutFunction(stdlink,"Plus",2);
>> MLPutReal(stdlink,2.1)
>> MLPutInteger(stdlink,2);
>>MLEndPacket(stdlink);
>>printf("MLReady = %d\n",MLReady(stdlink));
>>However when I try the following, it shows that there is no data to be
>>read on the stdlink and subsequent attempts to read data hang.
>>MLPutFunction(stdlink,"EvaluatePacket",1);
>> MLPutFunction(stdlink,"Get",1);
>> MLPutString(stdlink,"\"D:\\jimm\\svgcn018\\MathLink_USERSUR.mx\"");
>>MLEndPacket(stdlink);
>>printf("MLReady = %d\n",MLReady(stdlink));
>>I have tried issuing Get["D:\jimm\svgcn018\MathLink_USERSUR.mx"] from
>>within Mathematica and it works fine. The desired functions are
>>loaded.
>>Many thanks in advance for any assistance.
>>Jim