When dealing with old-school computer languages, I said the
part about implicit SI was optional. If you prefer to be
fully explicit, that's fine. In that case, the previous
example becomes:
in__m = 0.0254;
ft__m = 12 * in__m;
yd__m = 3 * ft__m;
L__m = 10 * yd__m;
L__ft = L__m / ft__m;
That's less concise but more bullet-resistant.
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When explaining it to non-experts, I draw the picture:
This is one of those all-too-rare cases where the
language of English aligns with the language of
algebra: The length is /divided/ by the units as
surely as a pizza is divided into slices.
This is yet another way of explaining why the "f = 3 y" is
perverse. The concept of /divide/ is crucial here, so we
should write
L/ft = 3 L/yd
with the units in the denominator.