Hi,

what is the reason the label direction prefix variables (rt, bot,
llft, etc.) are prefixed with mpfun_ in MkIV (mp-mlib.mpiv)? When
new directional prefixes are being defined it fails when mplib is
used unless the mpfun_ prefix is added. And likewise, code using the
mpfun_ prefix fails on traditional MetaPost.

Is this prefix required? It breaks old code and required a branch in
every new project. And I don't really see a reason for this
incompatibility. Here is an example defining a new direction “foo”:

\starttext
  \startMPcode
    label("first", origin);

    %% MkIV
    %% pair mfun_laboff.foo ; mfun_laboff.foo := (.5,-1) ;
    %% mfun_labxf.foo := mfun_labyf.foo := 1 ;

    %% MkII
    pair laboff.foo ; laboff.foo := (.5,-1) ;
    labxf.foo := labyf.foo := 1 ;

    label.foo("second", origin);
  \stopMPcode
\stoptext

Marco