boxp

Arguments: object

Returns t if the argument is a box object and returns nil otherwise.

See the description of the make-box for more information on boxes.

Warning about positions created by the with-boxes and with-positions-and-boxes

boxp should not be called on objects created by the macros with-boxes and with-positions-and-boxes. The return value of those functions is undefined for objects created by the macros because type information for such objects is sacrificed to achieve the non-consing efficiency of stack allocation.

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This page was not revised from the 9.0 page.
Created 2015.5.21.