(j3.2006) (SC22WG5.5038) Decision on Units TS proposal

Tobias Burnus burnus
Thu Jul 25 04:11:07 EDT 2013

Van Snyder wrote:
> As you might guess, my sponsors were disappointed that the proposal for a TS concerning units of measure in Fortran did not go forward. The are curious to know the reasons for opposition to a project with a
> schedule independent from the standard.

Personally, I have a mixed feeling about units: On one hand they are 
neat. They provide some cross checking, the conversion functions can be 
helpful and - especially for testing outputting the unit with I/O and 
the conversions are useful. On the other hand, implementing all the 
features suggested in N1970 will be a very large effort for compiler 
implementers - and I fear that it will also divert the attention of the 
committee from more pressing issues. Weighting the pros and cons, my 
vote is a weak "no".

I assume that others have similar feelings about this feature - hence, 
the opposition to the proposal.


PS: You wrote in N1970 that "Incorrect use of physical units is the 
third most common error in scientific or engineering software". I wonder 
where the numbers come from and what are first two. With the software I 
had to do with, "<" instead of ">", missing terms, wrong signs and 
similar issues seem to play a much larger role than units. - More common 
than those are of course out of bounds, uninitialized variables and 
other such problems.

PPS: At least two of the codes I used, have internally atomic units 
(hbar = 1, electron charge = 1, Bohr radius = 1, electron mass =1. As 
alpha has to remain at ~1/137 [unitless!], the speed of light c = 
1/alpha; energy and time are measure in units of 1). Given that most 
expressions are done unitless (conversion factor is 1), I wonder whether 
the programmers would move to your proposed units feature in those 
codes, if it were available.

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