[racket] typed/racket request for type for 'fourth' [and 1 more messages]

From: Sam Tobin-Hochstadt (samth at ccs.neu.edu)
Date: Tue Dec 13 14:49:39 EST 2011

On Tue, Dec 13, 2011 at 2:47 PM, Eli Barzilay <eli at barzilay.org> wrote:
> 10 minutes ago, John Clements wrote:
>> I know that there are some differences between the 'fourth' family
>> and the 'cadddr' family w.r.t. the kinds of arguments that they
>> accept, but it seems to me that if I have a (List Number Number
>> Symbol String), for instance, that I should be able to use 'fourth'
>> to get a String.
> There's a point for `first', `second', etc to do the same as `fourth'
> does in the above because the underlying functions require a list.
> But there's a counter point of having a (List ...) type in the first
> place.  So maybe `List' should also be limited to match what `fourth'
> is doing?  (IOW, the above `List' would be invalid, but if `fourth' is
> made to work as John expects then it would be valid...?)

I don't understand this paragraph at all.  That type specifies values
that `fourth' will always work on.
sam th
samth at ccs.neu.edu

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