[racket] Constructors for sequences

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Sun Apr 29 18:33:45 EDT 2012

On Apr 29, 2012, at 6:29 PM, Asumu Takikawa wrote:

> On 2012-04-29 12:43:48 -0400, Matthias Felleisen wrote:
>> What you're really saying is that sequence-map uses the wrong kind of type. Specifically, it should be polymorphic in the sequence constructor instead of mapping everything to the top of the class hierarchy (sequence).
> I don't think this is just a type issue. The sequence that is returned
> by `sequence-map` is lazy, even if the original sequence was not. That's
> why you can't get the original type.
> Cheers,
> Asumu

Why is it lazy? 

Can we add a strict one that is polymorphic (I apologize to the defenders of proper type terminology here for the applying this word to a dynamic aspect of Racket programs) in the sequence type-tag? 

-- Matthias

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