Assignment versus binding

[Rustom Mody]

On Tuesday, October 4, 2016 at 10:15:10 PM UTC+5:30, Steve D'Aprano wrote:
> On Tue, 4 Oct 2016 11:27 pm, Ben Bacarisse wrote:
> 
> > Haskell defines let (it's version of multiple mutually recursive
> > bindings) in terms of the least fix point of a lambda function whose
> > (pattern) parameter binds the expressions in the definitions.
> 
> It binds *the expression* itself? Not the value of the expression?


Lazy evaluation — one of the more touted features of Haskell — uses call-by-need
which is like memoized call-by-name:
https://en.wikipedia.org/wiki/Evaluation_strategy#Call_by_need
> 
> So Haskell uses some form of pass by name?
> 
> And (shamelessly using Python syntax) if I have a function:
> 
> 
> def spam(x):
>     print(x)
>     print(x+1)
> 
> 
> and then call it:
> 
> spam(time.sleep(60) or 1)
> 
> 
> it will sleep for 60 seconds, print 1, then sleep for another 60 seconds,
> then print 2. Is that right?


Strong type system would not allow mixing of effects and values like that