handle calls to the callback function in OpenMaple - Maple 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

callbackx2+y

See Also

CustomWrapper, errorCallBack, OpenMaple, OpenMaple/C/API, OpenMaple/C/Examples, queryInterrupt, readLineCallBack, redirectCallBack, StartMaple, statusCallBack, streamCallBack, textCallBack


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