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Re: [Scheme-reports] Some comments after reading the r7rs public draft

On Mon, Jun 11, 2012 at 7:57 AM, Per Bothner <per@x> wrote:
In Kawa:

Implicit forcing happens for:

  I agree that making a promise with an immediate value could evaluate to that immediate instead of creating a promise. But in general I think that a promise have to be opaque until forced and that it is worth to have a disjoint type for promises and to be able to check if an object is a promise or not.  IMHO for any other usage auto-forcing in primitives strongly sounds as being in the "it seems a good idea at that time" department: auto-forcing means that primitives have to check if something is a promise and forcing it in that case, adding this check add a cost and it has deep impact on the language semantics.

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