On Sat, Mar 1, 2014 at 4:30 PM, Mark H. Harris <harrismh...@gmail.com> wrote:
> hi Chris, yeah... well think again of the switch block in C... the switch
> block selects a branch based on an integral number (int character) that is
> generally a return code from a function. The function hides all of that
> logic. The function runs and returns a "number" which is passed to the switch
> block. That number generally corresponds to a DEFINE constant at the top or
> in the header... so we get something really readable:
>
> x = somefunc()
> switch (x):
> case: CONSTANT1
> call blah blah
> case: CONSTANT2
> call blah blah blah
> default
> blah
Okay. So you'd do that to make this more readable. Here's the original:
if (n**2 < D(1)):
a = __atan__(n)
elif (n == D(1)):
a = gpi/4
elif (n == D(-1)):
a = -(gpi/4)
elif (n < D(-1)):
a = __atan__Lt_neg1__(n)
else:
a = __atan__Gt_1__(n)
Now let's see. Your code doesn't perfectly translate, so I'm having to
guess a bit here.
GT_1 = object()
LT_n1 = object()
IS_1 = object()
IS_n1 = object()
def categorize(n):
if (n**2 < D(1)):
return None
elif (n == D(1)):
return IS_1
elif (n == D(-1)):
return IS_n1
elif (n < D(-1)):
return LT_n1
else:
return GT_1
switch categorize(x):
case GT_1:
__atan__Gt_1__(x)
# Not sure which you mean, this
case LT_n1:
__atan__Lt_neg1__(x)
# or this
case LT_1:
__atan__Lt_1__(x)
# So I have both, ish.
case IS_1:
a = gpi/4
case IS_n1:
a = -gpi/4
default:
# Presumably this should be a=?
__atan__(x)
Please copy and paste this, and then edit it so the two actually do
exactly the same thing. And then, if you please [1], explain to me how
the second one is more readable. It still has the exact same if/elif
tree, because there's no other way to figure out which constant you
should have for the switch; and as well as that, it exhibits an
appalling degree of Soft Coding[2], and it's roughly three times as
much code. If you want to change anything, you potentially have to
edit three places: the list of constants at the top, the condition
function, and the switch.
This can't be your idea of readability. Show me where I'm wrong.
ChrisA
[1] Steven D'Aprano unwittingly quoted HMS Pinafore a few posts back.
I'm now doing it consciously, for I hold that (on the seas) the
expression "if you please" a particularly gentlemanly tone implants.
[2] http://thedailywtf.com/Articles/Soft_Coding.aspx
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