The Fairbairn threshold is the point at which the effort of looking up or
keeping track of the definition is outweighed by the effort of rederiving
it or inlining it.
The term was in much more common use several years ago.[...]
The primary use of the Fairbairn threshold is as a litmus test to avoid
giving names to trivial compositions, as there are a potentially explosive
number of them. In particular any method whose definition isn't much longer
than its name (e.g. fooBar = foo . bar) falls below the threshold.The Fairbairn threshold is named after Jón Fairbairn, one of the original Haskell committee members.