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Diffstat (limited to 'docs/users_guide/exts/negative_literals.rst')
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1 files changed, 23 insertions, 0 deletions
diff --git a/docs/users_guide/exts/negative_literals.rst b/docs/users_guide/exts/negative_literals.rst new file mode 100644 index 0000000000..27a31c9b61 --- /dev/null +++ b/docs/users_guide/exts/negative_literals.rst @@ -0,0 +1,23 @@ +.. _negative-literals: + +Negative literals +----------------- + +.. extension:: NegativeLiterals + :shortdesc: Enable support for negative literals. + + :since: 7.8.1 + + Enable the use of un-parenthesized negative numeric literals. + +The literal ``-123`` is, according to Haskell98 and Haskell 2010, +desugared as ``negate (fromInteger 123)``. The language extension +:extension:`NegativeLiterals` means that it is instead desugared as +``fromInteger (-123)``. + +This can make a difference when the positive and negative range of a +numeric data type don't match up. For example, in 8-bit arithmetic -128 +is representable, but +128 is not. So ``negate (fromInteger 128)`` will +elicit an unexpected integer-literal-overflow message. + + |