[FP] Rewriting name bindings as expressions

[Richard Davies]

Greg Ewing wrote:
> Richard Davies wrote:
> > 
> > ans = []
> > for x in range(10):
> >    y = x*x
> >    ans.append(y+1)
> > 
> > We can rewrite this as a list comprehension
> > but ... how do we do so whilst binding y to x*x
> 
> ans = [y+1 for x in range(10) for y in (x*x,)]

This certainly solves the stated problem brilliantly,
but isn't so good in the general case of rewriting
name bindings as expressions when there aren't any
lists involved.

For instance, the ML

z = let y = x+1 in y+y*y

becomes

z = [y+y*y for y in x+1,][0]

which is good, but could be nicer if we never had to
bring lists into it...

Richard.