I may be missing something obvious.
Midje has a checker that lets users say things like
(fact (my-computation) => (roughly 15 2))
Where the first number in `roughly` is the target number and the second is an
acceptable range around that target. Part of what the checker does in 1.2 is
this:
(<= expected (+ actual delta))
Now, Midje is a service. If the 1.3 user has taken care to use
promoting-to-bignum arithmetic, it would be rude to blow up if `actual` happens
to be a regular integer but adding `delta` to it causes an overflow. I should
use promoting-to-bignum addition. In Clojure 1.3, thats +'. In 1.2, it's +.
I can't use the token +' because it doesn't exist in 1.2:
> java.lang.ClassCastException: clojure.lang.Symbol cannot be cast to
> java.lang.Number (NO_SOURCE_FILE:0)
I can't use the token + because that blows up in the boundary case under 1.3
(but not under 1.2).
One thought is variations of code like this:
> (if (clojure-1-3?)
> (def +M +')
> (def +M +)
This causes amusing results because of the quote. I haven't found a variation
that works.
So what should a library writer who wants to honor the choices of his users do?
-----
Brian Marick, Artisanal Labrador
Now working at http://path11.com
Contract programming in Ruby and Clojure
Occasional consulting on Agile
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