Performance/Modules

Haskell Performance Resource Constructs: Data Types - Functions Overloading - FFI - Arrays Strings - Integers - I/O Floating point - Concurrency Modules - Monads Techniques: Strictness - Laziness Avoiding space leaks Accumulating parameter Implementation-Specific: GHC - nhc98 - Hugs Yhc - JHC

Use an explicit export list

(note: this only applies to compilers based on separate compilation like GHC, not to those based on whole-program compilation like JHC).

If you do not have an explicit export list in a module, the compiler must assume that everything in that module will be exported. This disables various useful optimisations:

• If a function is used only once in the current module, and not exported, there is no penalty for inlining the function at its single use point.

• If a function is not used at all, and not exported, its definition can be discarded.

• The compiler has more flexibility regarding calling conventions and the like for functions that are not visible beyond the current compilation unit.