Jan Vroonhof <vroonhof(a)math.ethz.ch&gt; writes: Oh. Yes. Now I remember. One thing is, we haven't really agreed the marker behaviour were problems. Should (+ <marker> 0) really be guaranteed to convert a marker to integer? Is it acceptable that it hoses all other optimizations for that special case? I've always considered the marker arithmetics a relic from ancient times when someone thought it oh-so-cool to be able to increment a marker or compare it to a number or another marker without bothering to call `marker-position'. The marker arithmetics is important for backward compatibility, but in this case we can just as well document that the result types should not be relied on; they are numerically correct, but their type cannot be known in advance and can depend on whether the code is interpreted or compiled.