[Haskell-cafe] negate and -

[Matthew William Cox]

On Thu, 17 May 2007 13:50:15 -0300
Maurí­cio <briqueabraque at yahoo.com> wrote:

> Hi,
> 
> Haskell language reference says the special -
> operator translates to negate. However, this:
> 
> (+ negate 5) 5

Function application binds tightest, so this is equivalent to:
(+ (negate 5)) 5

> 
> works but this:
> 
> (+ -5) 5

In this context, it's trying to parse - as the binary subtraction operator. The special treatment of - in its unary context is that (-5) is (negate 5) and not the section ((-) 5)

> 
> is not valid. Why?
> 
> Thanks,
> Maurício
> 
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-- 
Matthew William Cox <matt at mattcox.ca>