Why is the left-arrow thin but right arrow fat?

[Haoyi Li]

I've always wondered why

<- =>

are considered language "keywords", while

<= ->

are left up to the developer to overload. Purely aesthetically, it seems that the "special" arrows should be either both fat or both thin, while the user-definable ones should be the opposite. 

Is there a reason (historical or otherwise) that they picked one-fat and one-thin arrow to be special, and left the other arrows (again one fat and one thin) to be user-definable?

-Haoyi

[Dave]

I think '<-' means only 'bind' while '=>' can be used as 'bind' in a
function literal, but also in pattern matchings//error handling or
self reference or by-name parameters.

'=>' is like '_' which can have multiple meanings/uses dependent on
its context.

[Andrés Testi]

'<-' also means pattern matching (in for comprehensions). I'm also wondered by the <-/=> inconsistency. 

[Dennis Haupt]

too late to change it now *evil laughter*

2014/1/2 Andrés Testi <andres....@gmail.com>

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[Dennis Haupt]

to give useful information:

<- is used for pattern matching

blah(a->b) is sugar for blah((a,b)) which is sugar for blah(Tuple2(a,b)) which is sugar for blah(Tuple2.apply(a,b))

blah(a => b) is creating a function

the only unused symbol is <=, because this one is "taken" by "lessThanOrEqual"

(i have no proof this was the intention)

2014/1/2 Dennis Haupt <d.ha...@gmail.com>