[Haskell-cafe] Magic values, WAS: Encrypting streamed data
monkleyon at gmail.com
Thu Jul 6 13:09:17 UTC 2017
> It's got some magic values in a few places (especially that 65!)
Off topic, but sometimes when I find myself using magic values I
can't/won't get rid off, I'll just apply the good old habits learned in
Java times. For example you might find a section at the top of a file
with things like
_DAYS_IN_A_WEEK_ , _KNOWN_SIZE_OF_POINT_ :: INT-- | Seems to be a good
approximation for now _DAYS_IN_A_WEEK_ = 7 -- | When you ask "What's the
point", this will not answer your question. _KNOWN_SIZE_OF_POINT_ = 65
Uppercase makes it easy to identify these as constants/magic values. The
underscore in front works as an initial lowercase letter so they can be
used as values despite uppercase.
The goal is not necessarily to make these values easy to change, but to
add documentation to usage sites.
It's unnecessary In such a quick demonstration, but I wanted to take the
opportunity to throw in my _VALUE_OF_CONTRIBUTION_IN_CENTS_ cents
because I haven't seen others do something like this.
PS: The underscore does introduce its own error message though.
• Found hole: _VALUE_OF_CONTRIBUTION_IN_CENTS_ :: Double
Or perhaps ‘_VALUE_OF_CONTRIBUTION_IN_CENTS_’ is mis-spelled, or not in scope
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