callBackCallBack - Maple Programming Help

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callBackCallBack

handle calls to the callback function in OpenMaple

 Calling Sequence callBackCallBack(data, output)

Parameters

 data - user_data pointer passed to StartMaple (void*) output - text version of parameters (char*)

Description

 • This OpenMaple function is part of the MCallBackVector structure passed as an argument to StartMaple.
 • The callBackCallBack function executes when the Maple callback function is evaluated.  The callback function is application dependent, and can do whatever the driving application directs it to do.
 • The prototype for the function you can assign to the entry in the MCallBackVector must look like the following.

 char * M_DECL callBackCallBack( void *data, char *output )

 • The output parameter contains the text version of the parameters passed to the Maple callback function.
 • On return, the callBackCallBack function returns either a NULL pointer or a pointer to a string containing a valid Maple expression. If the callBackCallBack function returns NULL, the Maple callback function returns nothing.  Otherwise the return value is parsed assuming it contains a Maple command string.  Maple parses the expression but does not evaluate it, and returns it as the result of the callback function.
 • This function can be used to explicitly pass intermediate values of a computation to your code and to return a value to Maple.
 • If no callBackCallBack function is provided, any attempt to execute the Maple callback function produces an error (reported using the errorCallBack function or textCallBack function).
 • The data parameter contains the same data as passed to StartMaple in the user_data parameter.
 • Source code for a callBackCallBack example is provided in the samples/OpenMaple/HelpExamples subdirectory of your Maple installation.

Examples

 > $\mathrm{callback}\left({x}^{2}+y\right)$