On Jan 21, 2008, at 10:52 PM, Brendan Eich wrote: > On Jan 21, 2008, at 8:02 PM, Maciej Stachowiak wrote: > >> On Jan 21, 2008, at 12:35 PM, Brendan Eich wrote: >> >>> Conversions (implicit and hardcoded among the >>> built-in types representing and wrapping primitives) that might >>> defeat PTC may not be evident until runtime, where the result would >>> be a TypeError or possibly a new Error subtype. >> >> Isn't this case (implicit conversion) exactly what motivated the idea >> that programmers may not be able to easily tell if a call is in tail >> position? > > > Indeed: > > "ES4 has proper tail calls, but their constraints are sometimes > subtle, especially with regard to conversions or type checks > inserted at the return point. It may be that the "Explicit Is Better > Than Implicit" principle once again finds application here." > > First paragraph in http://bugs.ecmascript.org/ticket/323. Again, the > ticket is just sitting there, you don't need me transcribing it into > this list :-/.
What I meant to point out is that the motivating use case for additional up-front checking can't in general be checked until runtime, which somewhat undermines the point you made that many non- tail cases could be caught at compile time. Cheers, Maciej _______________________________________________ Es4-discuss mailing list Es4-discuss@mozilla.org https://mail.mozilla.org/listinfo/es4-discuss
