Kay Schluehr wrote: > Juan R. wrote: > > A bit ambiguous my reading. What is not feasible in general? Achieving > > compositionality? > > Given two languages L1 = (G1,T1), L2 = (G2, T2 ) where G1, G2 are > grammars and T1, T2 transformers that transform source written in L1 or > L2 into some base language > L0 = (G0, Id ). Can G1 and G2 be combined to create a new grammar G3 > s.t. the transformers T1 and T2 can be used also to transform L3 = (G3 > = G1(x)G2, T3 = T1(+)T2) ? In the general case G3 will be ambigous and > the answer is NO. But it could also be YES in many relevant cases. So > the question is whether it is necessary and sufficient to check whether > the "crossing" between G1 and G2 is feasible i.e. doesn't produce > ambiguities.
See, we don't have this problem in Lisp, unless some of the transfomers in T1 have names that clash with those in T2. That problem can be avoided by placing the macros in separate packages, or by renaming. In In the absence of naming conflicts, the two macro languages L1 and L2 combine seamlessly into L3, because the transformers T are defined on structure, not on lexical grammar. The read grammar doesn't change (and is in fact irrelevant, since the whole drama is played out with objects, not text). In L1, the grammar is nested lists. In L2, the grammar is, again, nested lists. And in L3: nested lists. So that in fact, at one level, you don't even recognize them as being different languages, but on a different level you can. The problems you are grappling with are in fact created by the invention of an unsuitable encoding. You are in effect solving a puzzle that you or others created for you. -- http://mail.python.org/mailman/listinfo/python-list
