Arabbit.427 net.lang.apl utzoo!decvax!duke!harpo!ihnss!houxi!npois!alice!rabbit!ark Thu Apr 8 10:50:17 1982 Re: apl parsing I meant the hardest part of MACHINE parsing, because your typical parser changes the characters to tokens left to right and then parses during execution right to left. When parsing right to left and you've seen ...]-X, you do indeed have to find the matching [ and look beyond it before you can figure out what to do about the -. You might argue "But you can classify the - as monadic or dyadic on the left to right scan". Indeed you might! But you can't in such simple cases as A-B, because you don't know until you get there whether A is a variable or a monadic function. It was a long time before IBM APL knew how to handle +/[X]-Y ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.