[plt-scheme] symbols redefined in SRFIs

From: Eli Barzilay (eli at barzilay.org)
Date: Tue Oct 24 00:31:38 EDT 2006

On Oct 23, Bill Wood wrote:
> On Mon, 2006-10-23 at 22:12 -0400, Eli Barzilay wrote:
> > On Oct 24, Dan Muresan wrote:
> > > >   * the ability to catch bugs in code that wants to use lists of equal
> > > >     length
> > > 
> > > (you mean unequal length)
> > 
> > No -- code that wants equal-length lists, but got unequal lengths
> > instead.  Before your change it raised an error and got a happy
> > programmer.  After your change you get a bug that propagates further
> > and becomes harder to find.
> Doesn't that work both ways?  [...]

Of course.  Like I said, the question is which version gives you the
the most benefits.  (And allowing more inputs is not always more

> I have a weakly justifiable preference for the CL behavior on the
> grounds that a) maps over unequal length lists have a sensible
> specification and b) robust design favors weakening the input
> constraint.

Justifications for either side would be good (BTW, I'm don't have a
preference either way -- I'm not sure which version is better.), but I
don't think that your arguments hold.  Your first argument is bogus,
since `map' over equal length lists is also sensible.  The second
argument is questionable too -- and there are (IMO) too many languages
that suffer from that when they deal with strings, integers, and `+'.
For example, where's the bug in this code

  function add1_to_x() {
    document.form.y.value = document.form.x.value + 1;

          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!

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