Now, that we have this helper function that should have been
introduced long ago, we can make some more expressions
more idiomatic.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
There were helper functions to access O2 and He component fractions.
Add another one for N2. Indeed, this can be used in three cases, where
N2 was deduced indirectly.
Moreover, add a general accessor with a gas_component argument.
This will be used by the filter code to filter for gas components.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
But only functions that operate only on gases. Functions concerning
cylinders or dives remain in dive.c or are moved to equipment.c
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
