X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fglasgow_exts.xml;h=a1930880d6658114bc66414204c77663ed43fc14;hb=da43a382ccc7d3c57068976c312dc583fddc7498;hp=172d6ff3518ea73b52e13195f2876ca5fbe77df7;hpb=46809fa91667e952afe016e4cd704b21274241b4;p=ghc-hetmet.git diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml index 172d6ff..a193088 100644 --- a/docs/users_guide/glasgow_exts.xml +++ b/docs/users_guide/glasgow_exts.xml @@ -450,43 +450,6 @@ Indeed, the bindings can even be recursive. - - New qualified operator syntax - - A new syntax for referencing qualified operators is - planned to be introduced by Haskell', and is enabled in GHC - with - the - option. In the new syntax, the prefix form of a qualified - operator is - written module.(symbol) - (without NewQualifiedOperators this would - be (module.symbol)), - and the infix form is - written `module.(symbol)` - (without NewQualifiedOperators this would - be `module.symbol`. - For example: - - add x y = Prelude.(+) x y - subtract y = (`Prelude.(-)` y) - - The new form of qualified operators is intended to regularise - the syntax by eliminating odd cases - like Prelude... For example, - when NewQualifiedOperators is on, it is possible to - write the enumerated sequence [Monday..] - without spaces, whereas without NewQualifiedOperators this would be a - reference to the operator ‘.‘ - from module Monday. - - When is on, the old - syntax for qualified operators is not accepted, so this - option may cause existing code to break. - - - - @@ -4041,18 +4004,21 @@ The willingness to be overlapped or incoherent is a property of the instance declaration itself, controlled by the presence or otherwise of the and flags when that module is -being defined. Neither flag is required in a module that imports and uses the -instance declaration. Specifically, during the lookup process: +being defined. Specifically, during the lookup process: -An instance declaration is ignored during the lookup process if (a) a more specific -match is found, and (b) the instance declaration was compiled with -. The flag setting for the -more-specific instance does not matter. +If the constraint being looked up matches two instance declarations IA and IB, +and + +IB is a substitution instance of IA (but not vice versa); +that is, IB is strictly more specific than IA +either IA or IB was compiled with + +then the less-specific instance IA is ignored. Suppose an instance declaration does not match the constraint being looked up, but -does unify with it, so that it might match when the constraint is further +does unify with it, so that it might match when the constraint is further instantiated. Usually GHC will regard this as a reason for not committing to some other constraint. But if the instance declaration was compiled with , GHC will skip the "does-it-unify?" @@ -4062,18 +4028,6 @@ check for that declaration. These rules make it possible for a library author to design a library that relies on overlapping instances without the library client having to know. - -If an instance declaration is compiled without -, -then that instance can never be overlapped. This could perhaps be -inconvenient. Perhaps the rule should instead say that the -overlapping instance declaration should be compiled in -this way, rather than the overlapped one. Perhaps overlap -at a usage site should be permitted regardless of how the instance declarations -are compiled, if the flag is -used at the usage site. (Mind you, the exact usage site can occasionally be -hard to pin down.) We are interested to receive feedback on these points. - The flag implies the flag, but not vice versa. @@ -8242,7 +8196,7 @@ Here is an example: Use the debug flag to see what rules fired. If you need more information, then shows you -each individual rule firing in detail. +each individual rule firing and also shows what the code looks like before and after the rewrite. @@ -8827,7 +8781,8 @@ If you add you get a more detailed listing. - Use to see in great detail what rules are being fired. + Use or +to see in great detail what rules are being fired. If you add you get a still more detailed listing.