On Fri, Mar 2, 2012 at 4:47 AM, Marijn <hk...@gentoo.org> wrote: > One other thing > that could use some explanation is why racket uses phases in the first > place, given that other systems (I believe Larceny is the prime > example) have implemented a phase-less or phase-inferring macro system.
The short answer for this is to control the behavior of side effects at expansion time. In the presence of such side effects, correct phase-inference is impossible in the general case, and even in simpler cases, behavior changes depending on how the program is compiled. In Ikarus (which is where the phase inference work was done), the designers decided that such macros were not an important use case. While they are mostly not intended as tutorials, the two papers that talk about phases: Matthew's 2002 paper, Composable and Compilable Macros, and Ryan, Matthew and my 2007 paper mentioned earlier in this thread, provide a useful overview of what can be accomplished with phases. -- sam th sa...@ccs.neu.edu ____________________ Racket Users list: http://lists.racket-lang.org/users
