Source : Free On-Line Dictionary of Computing

inline
     
         (Or "unfold") To replace a {function} call with
        an instance of the function's body.  {Actual argument}
        expressions are substituted for {formal parameters} as in
        {beta reduction}.  Inlining is usually done as a
        {compile-time} transformation.
     
        If done recklessly (e.g. attempting to inline a {recursive}
        function) the {compiler} will fail to terminate.  If done
        over-enthusiastically the code size may increase
        exponentially, e.g. if function f calls g twice, and g calls h
        twice and h is inlined in g which is inlined in f (in either
        order) then there will be four copies of h's body in f.
     
        See also {linear argument}, {unfold/fold}.
     
        (1994-11-03)