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0 pointsJtsummers6mo ago0 comments

That's still not really answering my question for you, which was less clear than intended. To restate it:

> The one place this advice falls down is security - having functions that do things without verifying preconditions are exploitable

My understanding of your comment was that "this advice" is CQS. So you're saying that CQS commands do not verify preconditions and that this is a weakness in CQS, in particular.

Where did you get the idea that CQS commands don't verify preconditions? I've never seen anything in any discussion of it, including my (admittedly 20 years ago) study of Eiffel.

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hinkley6mo ago

And I remain confused by your confusion.

If A then B()

Versus

B()

Somewhere there’s a B without the associated query. Call it what you want, at the bottom of the tree two roads diverge. Otherwise there is no Separation in your CQS.

ETA: once you get down to the mutation point you aren’t just dealing with immutable data. You’re moving things around, often plural.

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