This is one of the annoying things about Haskell code -- since many Haskell programmers come from math backgrounds, they tend to use very short variables, often one letter or a letter and a number, where a programmer would use a descriptive variable. Perhaps more annoyingly, as a result of this lineage, it's become part of the convention, so even those who come from a non-math background tend to use short, mathy variable names.