PUREP and MACROMEMO

[Alan Bawden <ALAN at MIT-MC>]

    Date: 15 December 1980 10:02-EST
    From: Robert W. Kerns <RWK at MIT-MC>

    For the Nth time tonight, I have been shafted by macros which
    expand into code including other macro calls which want to
    displace.  If part of the expansion of a macro is constant, then
    that expansion will be pure.  If that pure portion also contains a
    call to a macro which wishes to displace, you lose your ass.
    Let's DO something about this!

Allow me to revive the suggestion that DISPLACE should check for the
purity of its first argument and not rplac in that case.