Changes between Version 10 and Version 11 of PrefixMinusResolution

Timestamp:

07/14/10 04:49:49 (3 years ago)

Author:

maeder

Comment:

more comments on nhc98

PrefixMinusResolution

@@ -61 +61 @@
 }}}
 
-x7 are currently rejected by Hugs and ghc. Two solutions are possible. Since "-" should just bind weaker than multiplication the possibility "-(4 # 5)" cannot be justified, thus "(-4) # 5" should be the unique solution. 
+x7 are currently rejected by Hugs and ghc. Two solutions are possible. By accident nhc98 resolves this as "-(4 # 5), because # is not left-associative.
+I think associativity should only matter for two infix operators. Since "-" should just bind weaker than multiplication "(-4) # 5" should be the unique solution!
+
+{{{
+infixr # 6
+(#) = (-)
+x8 = - 4 # 5 # 6
+}}}
+
+x8 will be resolved as "(- 4) # (5 # 6)" like it would for any right-associative operator # with lower precedence, too. For any
+''non-associative'' operator # "- 4 # 5 # 6" is rejected like "4 # 5 # 6" or "-(4 # 5 # 6)" would be.
 
 Surely, one can always disallow "confusing" resolutions, but if we reject "- 4 # 5", we can also reject "- 4 - 5" or "`- 4 ^ 5`".
-Associativity seems wrong to consider for the unary minus function. (But it is an option to simple use the way of Hugs for ghc, too.)
+Associativity seems wrong to consider for the unary minus function. (But it is an option to simple use the way of Hugs or nhc98 for ghc, too.)
 
 As a further option it is possible to support multiple prefix minus application. ("4 * - - 5" can be resolved in the same way as