John Meacham wrote:
On Mon, May 14, 2007 at 10:19:07AM +0100, Simon Marlow wrote:
Really? I'm beginning to have second thoughts about the proposed change to
negation for Haskell'. The main reason, and this isn't pointed out as well
as it should be on the wiki, is that x-1 will cease to be an
On Mon, May 21, 2007 at 10:33:56AM +0100, Simon Marlow wrote:
I think that we could easily remove the '3e4' lexical syntax though, since
'3*10^^4' works just as well (I often write the latter anyway) (and guess
what, I just had to look up the difference between ^ and ^^, only to
discover I
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John Meacham wrote:
another option would be to only count it as a negative if there is a
non-identifier character preceeding it. A little ugly. but still better
than the current situation IMHO.
I think Ghc's lexer Alex can do this although this
On Mon, May 14, 2007 at 10:19:07AM +0100, Simon Marlow wrote:
Really? I'm beginning to have second thoughts about the proposed change to
negation for Haskell'. The main reason, and this isn't pointed out as well
as it should be on the wiki, is that x-1 will cease to be an infix
On Thu, May 17, 2007 at 06:40:04PM +0200, Twan van Laarhoven wrote:
Simon Marlow wrote:
...
Really? I'm beginning to have second thoughts about the proposed change
to negation for Haskell'. The main reason, and this isn't pointed out
as well as it should be on the wiki, is that x-1 will
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Iavor Diatchki wrote:
Hello,
I agree with Simon on this one: x-1 should parse as expected (i.e.,
the infix operator - applied to two arguments x and 1). Having
this result in a type error would be confusing to both beginners and
working Haskell
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I wrote:
negative :: Num a = Integer - a
negative a = fromInteger (negate a)
Oops, I forgot Rational literals, they make things a little more
complicated :(
Isaac
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Twan van Laarhoven wrote:
There is one other alternative for parsing:
- is a unary minus if and only if it is
a) preceded by whitespace or one of [({;,, and
b) not followed by whitespace.
So:
x - 1 ==(-) x 1
x-1
John Meacham wrote:
On Wed, Apr 11, 2007 at 09:05:21AM +0100, Simon Marlow wrote:
I definitely think that -1# should be parsed as a single lexeme.
Presumably it was easier at the time to do it the way it is, I don't
remember exactly.
I'd support a warning for use of prefix negation, or
Hello,
I agree with Simon on this one: x-1 should parse as expected (i.e.,
the infix operator - applied to two arguments x and 1). Having
this result in a type error would be confusing to both beginners and
working Haskell programmers.
I think that if we want to change anything at all, we
On Wed, Apr 11, 2007 at 09:05:21AM +0100, Simon Marlow wrote:
I definitely think that -1# should be parsed as a single lexeme.
Presumably it was easier at the time to do it the way it is, I don't
remember exactly.
I'd support a warning for use of prefix negation, or alternatively you
Okay, first steps:
1. A Trac ticket (#1318,
http://hackage.haskell.org/trac/ghc/ticket/1318) (is feature request a
good category, versus task?)
2. A test-case to make sure I don't break anything with existing '-'
syntax. I'm guessing it should go in
testsuite/tests/ghc-regress/parser/should_run/,
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Isaac Dupree wrote:
Simon Marlow wrote:
I definitely think that -1# should be parsed as a single lexeme.
Presumably it was easier at the time to do it the way it is, I don't
remember exactly.
I'd support a warning for use of prefix negation, or
Isaac Dupree wrote:
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Isaac Dupree wrote:
Simon Marlow wrote:
I definitely think that -1# should be parsed as a single lexeme.
Presumably it was easier at the time to do it the way it is, I don't
remember exactly.
I'd support a warning for use of
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Simon Marlow wrote:
So does this suggest that under a negation-is-part-of-numeric-token
regime, 123-456 should be two tokens (a positive number then a negative
number, here), as is signum-456 ...
Yes, absolutely.
[see note 1 at the end
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Er,
For the purpose of warnings, I would explicitly keep track, for
unqualified operator -, whether it was followed by a digit (which is
the unique and certain determiner that a numeric literal follows. Octal
and hexadecimal start with 0c for
I definitely think that -1# should be parsed as a single lexeme. Presumably it
was easier at the time to do it the way it is, I don't remember exactly.
I'd support a warning for use of prefix negation, or alternatively you could
implement the Haskell' proposal to remove prefix negation
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Simon Marlow wrote:
I definitely think that -1# should be parsed as a single lexeme.
Presumably it was easier at the time to do it the way it is, I don't
remember exactly.
I'd support a warning for use of prefix negation, or alternatively you
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Now I understand why negative unboxed numeric literals are parsed
weirdly, after poking around a little!
The parser parses all infix applications as right-associative,
regardless of fixity.
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Since the unary negation operator `-' is often considered a wart in
Haskell's syntax and in many cases saying negate is arguably clearer
anyway, I propose adding options to GHC to warn about its use. The only
case I don't normally want to be warned
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