-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Twan van Laarhoven wrote:
There is one other alternative for parsing: "-" is a unary minus if and only if it is a) preceded by whitespace or one of "[({;,", and b) not followed by whitespace.
So: x - 1 == (-) x 1 x-1 == (-) x 1 x -1 == x (negate 1) x -(1) == x (negate 1) x (-1) == x (negate 1) x (- 1) == x (\y -> y - 1)
Just an idea.
Indeed, and in some language syntax designs it would certainly be a good system for prefix operators. Existing parsers may have some difficulty. How about
{-comment-}-1 ? how about WeirdNumber{value=2,weird=True}-1 ?
Although likely to make any actual code work, it seems a bit complicated from the mindset of current Haskell parsing/lexing. "(b) not followed by whitespace." can be replaced by (b) followed by a digit if desired not to allow it for negating arbitrary expressions. Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGTJRgHgcxvIWYTTURAqpMAJ9rpCFwzOG/ZSF0qpM/hD/mFKrQ1wCfSRCK 2nKiBzRs/8thmgrdBT+SowA= =lFCl -----END PGP SIGNATURE-----