diff options
Diffstat (limited to 'docs/users_guide/bugs.rst')
| -rw-r--r-- | docs/users_guide/bugs.rst | 33 |
1 files changed, 26 insertions, 7 deletions
diff --git a/docs/users_guide/bugs.rst b/docs/users_guide/bugs.rst index 7ccb215d23..aee8dc5842 100644 --- a/docs/users_guide/bugs.rst +++ b/docs/users_guide/bugs.rst @@ -83,12 +83,6 @@ Context-free syntax (let x = 42 in x == 42 == True) -- The Haskell Report allows you to put a unary ``-`` preceding certain - expressions headed by keywords, allowing constructs like ``- case x of ...`` - or ``- do { ... }``. GHC does not allow this. Instead, unary ``-`` is allowed - before only expressions that could potentially be applied as a function. - - .. _infelicities-exprs-pats: Expressions and patterns @@ -143,7 +137,7 @@ group is generalised (`Haskell Report, Section 4.5.2 <http://www.haskell.org/onlinereport/decls.html#sect4.5.2>`__). Following a suggestion of Mark Jones, in his paper `Typing Haskell in -Haskell <http://citeseer.ist.psu.edu/424440.html>`__, GHC implements a +Haskell <https://web.cecs.pdx.edu/~mpj/thih/>`__, GHC implements a more general scheme. In GHC *the dependency analysis ignores references to variables that have an explicit type signature*. As a result of this refined dependency analysis, the dependency groups are smaller, and more bindings will @@ -348,6 +342,31 @@ The Foreign Function Interface single: hs_init single: hs_exit +.. _infelicities-operator-sections: + +Operator sections +^^^^^^^^^^^^^^^^^ + +The Haskell Report demands that, for infix operators ``%``, the following +identities hold: + +:: + + (% expr) = \x -> x % expr + (expr %) = \x -> expr % x + +However, the second law is violated in the presence of undefined operators, + +:: + + (%) = error "urk" + (() %) `seq` () -- urk + (\x -> () % x) `seq` () -- OK, result () + +The operator section is treated like function application of an undefined +function, while the lambda form is in WHNF that contains an application of an +undefined function. + .. _haskell-98-2010-undefined: GHC's interpretation of undefined behaviour in Haskell 98 and Haskell 2010 |