Multiple SAMs for same concept

Lawrence Kesteloot lk at
Thu Jul 15 20:34:26 PDT 2010

On Thu, Jul 15, 2010 at 5:56 PM, Reinier Zwitserloot
<reinier at> wrote:
> HashMap and Hashtable both
> implement the same interface, both do so entirely correctly, and yet they
> aren't compatible with each other in some regard - in this case, null
> keys/values.

Exactly, and if a function took a Map object it would know to defend
itself against null keys and values (for example, by not blindly
calling toString() on either). But imagine a signature-compatible
NonNullMap interface and some syntactic sugar that allowed developers
to trivially autowrap objects from one to the other. It'd be too easy
to send an object into a method that violated the contract of the

In any case, I think we agree that it shouldn't be completely
transparent, which is what I was objecting to. The variant with only #
appended is Perl-like magic noise to me, but I always prefer
explicitness at the expense of terseness.

(We need a variant of Godwin's Law:  "As an online programming
language discussion grows longer, the probability of a comparison
involving Perl approaches 1, and the person who brings it up has


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