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Comment by th | Hacker News Reader

> Without, conformance tests different interpretations of a spec lead to divergent behavior.

I think you mean either:

> Without conformance tests incorrect interpretations of a spec lead to divergent behavior

> Without conformance tests different interpretations of an ambiguous spec lead to divergent behavior.

Conformance tests should test specific behavior defined in the spec. Tests will never (or rarely) prove spec conformance but spec conformance should always prove test conformance.

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I have yet to encounter a spec that was not in some way ambiguous.

1 + 1 = 2 Is fairly unambiguous until you introduce operator overloading (and why i despise overloading).

> 1 + 1 = 2 Is fairly unambiguous until you introduce operator overloading (and why i despise overloading).

It is only unambiguous if you specify the numbering system you are using ;)

</pedantic>

Is there actually a notation and + operator for which 1 + 1 = 2 is ambiguous? Only being semi-rhetorical, I'd be interested to know if there is one. (Modular arithmetic is not considered ambiguous, at least not in the math neck of the woods.)

Not really answering your question, but more to the point of the discussion in my opinion, a() + b() could be ambiguous if a() and b() are functions with side effects and the evaluation order of the +-operator is not specified.

1 + 1 = 10b is what he's saying.

Yes, that's what I meant - even "1 + 1 = 2" can be ambiguous if no context is provided.

> 1 + 1 = 2 Is fairly unambiguous until you introduce operator overloading (and why i despise overloading).

What is it specifying—or, perhaps a better question, what would an implementation look like? It might be more precise to say "I have yet to encounter an implemented spec that was not in some way ambiguous."

1 + 1 != 2 if the 1s are magnitudes of vectors - if the directions are opposite, then they can be 0. In fact, 0 <= 1 + 1 <= 2 in that system.

That's not how addition works. You're either adding the vectors or you're adding the magnitudes. You don't get to sleight of hand by writing one and adding the other.

Overloading is a feature of natural language though, and therefore completely unavoidable in writing a spec.

Hee hee, your interpretation of his sentence is introducing ambiguities :)

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