register-lisp-value

Arguments: value &optional index

The value is stored in the table of foreign values at the requested index, if index is given; or in a free slot if index is not given. Two values are returned: the index and the previous value at that index (or nil if there was no previous value at that index).

Note that there is a distinction between registering a symbol and its value. To register the value of a symbol, one wants to evaluate the symbol. To register the symbol object itself, one must quote it. Thus

(ff:register-lisp-value 'my-symbol) 

registers the symbol my-symbol, whereas

(ff:register-lisp-value my-symbol) 

registers the (current) value of my-symbol. If one registers the value of a symbol and subsequently the value is changed, the change will not be reflected in the value returned by lisp_value() in C (described in foreign-functions.htm). If one registers a symbol, one must use special macros in C to access the value of the symbol.

See ftype.htm for information on foreign types in Allegro CL and foreign-functions.htm for general information on foreign functions in Allegro CL.

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Created 2012.5.30.