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Checking if 'C++ type stream' is valid when using Matlab Coder

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Juan Rojas
Juan Rojas 2013-2-20
I am using matlab coder to turn matlab code into C++. One desired function is to read a file. I can do so effectively by following the code found at:
http://www.mathworks.com/products/matlab-coder/examples.html?file=/products/demos/shipping/coder/coderdemo_readfile.html.
However, I would also like to check to make sure the stream is valid. In matlab I can simply do this by saying:
fid = coder.ceval('fopen', [FileName 0], ['a+t' 0]);
if(fid~=0)...
However, currently the compiler is telling me: "??? Expected either a logical, char, int, fi, single, or double. Found a coder.opaque."
I tried a few options:
if(fid)...
if(~fid)...
if(fid==NULL)...
But could not get it to work. Any ideas?

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回答（1 个）

Ryan Livingston
Ryan Livingston 2013-2-20
编辑：Walter Roberson 2013-2-20
Try:
fid = coder.opaque('FILE *','NULL')
NULL = coder.opaque('FILE *','NULL');
fid = coder.ceval(...);
if(fid == NULL)
...
after adding <stdio.h> in your project as you describe in your other post:
http://www.mathworks.com/matlabcentral/answers/64172-matlabl-coder-compilation-error-with-file
The error you are seeing is because the line:
if(fid~=0)
is trying to compare a coder.opaque, fid, to a double, 0.

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