[Haskell-cafe] What does "1 = 2" mean in Haskell?

Harendra Kumar harendra.kumar at gmail.com
Fri Feb 24 02:56:50 UTC 2017

My first guess was a pattern match, but it sounded a bit odd because there
is no explicit constructor in case of numbers.  If there were an explicit
constructor it would have been easier to imagine this as a pattern match.
This seems to be a weird side effect of the special handling of numbers.


On 24 February 2017 at 07:37, Brandon Allbery <allbery.b at gmail.com> wrote:

> On Thu, Feb 23, 2017 at 9:05 PM, Harendra Kumar <harendra.kumar at gmail.com>
> wrote:
>> Kids have this amazing ability to break any toy in minutes. I gave my
>> seven year old daughter ghci to play with and in a little while she said it
>> is broken:
>> >> let 1 = 2
>> >> 1
>> 1
>> >>
>> Earlier, I had explained to her about symbols and assigning values to
>> symbols, and I said numbers are not symbols. But when she came up with this
>> I could not explain what's going on. How can "1 = 2" be a valid equation?
>> Am I missing something fundamental here, or it is just broken?
> It's a pattern match. The match fails, but as it produced no bindings it
> cannot be observed and its success or failure is irrelevant.
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
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