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Not sure whether they used a value pattern.

typedef struct { float value; } meter;

typedef struct { float value; } feet;

Using strong typing, you can avoid passing values in wrong units.



The mars probe unit problem was mismatched between different software programs. One was telemetry reported by the spacecraft to the ground, the other was software on the ground that used this telemetry to perform calculations that reported the results with the incorrect units.

Maybe the answer is that strong typing should somehow continue outside of the individual programs and be embedded in file formats as well?


Yes. Any message exchanges should have type encoded like in ASN.1, but not sure whether NASA used such a format.


In C++, there are a few very nice libraries for computation with units, e.g.:

https://github.com/mpusz/mp-units

which does all sorts of checking, allows arithmetic with proper accounting for units and so on. But yes, the basic notion is wrapping things in structs which can't be simply assigned to each other.




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