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diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml
index dab683a..a193088 100644
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -3,8 +3,9 @@
language, GHCextensions, GHC
As with all known Haskell systems, GHC implements some extensions to
-the language. They are all enabled by options; by default GHC
-understands only plain Haskell 98.
+the language. They can all be enabled or disabled by commandline flags
+or language pragmas. By default GHC understands the most recent Haskell
+version it supports, plus a handful of extensions.
@@ -39,8 +40,7 @@ documentation describes all the libraries that come with GHC.
The language option flags control what variation of the language are
- permitted. Leaving out all of them gives you standard Haskell
- 98.
+ permitted.Language options can be controlled in two ways:
@@ -439,10 +439,10 @@ Indeed, the bindings can even be recursive.
'x'# has type Char#"foo"# has type Addr#3# has type Int#. In general,
- any Haskell 98 integer lexeme followed by a # is an Int# literal, e.g.
+ any Haskell integer lexeme followed by a # is an Int# literal, e.g.
-0x3A# as well as 32#.3## has type Word#. In general,
- any non-negative Haskell 98 integer lexeme followed by ##
+ any non-negative Haskell integer lexeme followed by ##
is a Word#. 3.2# has type Float#.3.2## has type Double#
@@ -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)
- (in Haskell 98 this would
- be (module.symbol)),
- and the infix form is
- written `module.(symbol)`
- (in Haskell 98 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 in Haskell 98 this would be a
- reference to the operator ‘.‘
- from module Monday.
-
- When is on, the old Haskell
- 98 syntax for qualified operators is not accepted, so this
- option may cause existing Haskell 98 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.