Check assertion value for debugging purposes
Like the ANSI® C assert macro, mxAssert checks the value of an assertion, and continues execution only if the assertion holds. If expr evaluates to logical 1 (true), mxAssert does nothing. If expr evaluates to logical 0 (false), mxAssert terminates the MEX-file and prints an error to the MATLAB® command window. The error contains the failed assertion's expression, the file name and line number where the failed assertion occurred, and the error_message string. The error_message string allows you to specify a better description of why the assertion failed. Use an empty string if you do not want a description to follow the failed assertion message.
The mex script turns off these assertions when building optimized MEX-functions, so use this for debugging purposes only. Build the MEX-file using the syntax mex -g filename in order to use mxAssert.
Assertions are a way of maintaining internal consistency of logic. Use them to keep yourself from misusing your own code and to prevent logical errors from propagating before they are caught; do not use assertions to prevent users of your code from misusing it.
Assertions can be taken out of your code by the C preprocessor. You can use these checks during development and then remove them when the code works properly, letting you use them for troubleshooting during development without slowing down the final product.