GNU Emacs Lisp Reference Manual

28.2: Predicates on Markers

You can test an object to see whether it is a marker, or whether it is either an integer or a marker. The latter test is useful in connection with the arithmetic functions that work with both markers and integers.

Function: markerp object

This function returns t if object is a marker, nil otherwise. Note that integers are not markers, even though many functions will accept either a marker or an integer.

Function: integer-or-marker-p object

This function returns t if object is an integer or a marker, nil otherwise.

Function: number-or-marker-p object

This function returns t if object is a number (either kind) or a marker, nil otherwise.