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Re: [Scheme-reports] Draft 3 Comments: Chapter 4
On Wed, 27 Jul 2011, Denis Washington wrote:
> Thinking about it, leaving this unspecified makes sense as one couldn't
> use "when" and "unless" to return a value from a procedure anyway
> without risking an unspecified return value (if the test evaluates to #f
> or #t, respectively).
> On the other hand, "begin" in an expression context also a sole
> side-effect construct (otherwise, all expressions except the last in a
> "begin" form would be useless) and still returns the last expression's
> result. Given that "when" and "unless" are very similar, I find it to be
> pretty intuitive if they have the same behavior. I'm undecided.
The difference is that BEGIN in an expression context always has a last
expression. On the other hand, WHEN with a #f test is more like an empty
Could you maybe come up with a use case illustrating the usefulness of your
proposed change? I can't think of anything myself.
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