Name package:base -is:exact

Gets the type constructor including the module

Gets the unqualified type constructor: drop *.*.*... before name

Computation getProgName returns the name of the program as it was invoked. However, this is hard-to-impossible to implement on some non-Unix OSes, so instead, for maximum portability, we just return the leafname of the program as invoked. Even then there are some differences between platforms: on Windows, for example, a program invoked as foo is probably really FOO.EXE, and that is what getProgName will return.

withProgName name act - while executing action act, have getProgName return name.

The Haskell implementation with which the program was compiled or is being interpreted.

Stable names are a way of performing fast (O(1)), not-quite-exact comparison between objects. Stable names solve the following problem: suppose you want to build a hash table with Haskell objects as keys, but you want to use pointer equality for comparison; maybe because the keys are large and hashing would be slow, or perhaps because the keys are infinite in size. We can't build a hash table using the address of the object as the key, because objects get moved around by the garbage collector, meaning a re-hash would be necessary after every garbage collection.

An abstract name for an object, that supports equality and hashing. Stable names have the following property:

• If sn1 :: StableName and sn2 :: StableName and sn1 == sn2 then sn1 and sn2 were created by calls to makeStableName on the same object.

The reverse is not necessarily true: if two stable names are not equal, then the objects they name may still be equal. Note in particular that makeStableName may return a different StableName after an object is evaluated. Stable Names are similar to Stable Pointers (Foreign.StablePtr), but differ in the following ways:

• There is no freeStableName operation, unlike Foreign.StablePtrs. Stable names are reclaimed by the runtime system when they are no longer needed.
• There is no deRefStableName operation. You can't get back from a stable name to the original Haskell object. The reason for this is that the existence of a stable name for an object does not guarantee the existence of the object itself; it can still be garbage collected.

Equality on StableName that does not require that the types of the arguments match.

Convert a StableName to an Int. The Int returned is not necessarily unique; several StableNames may map to the same Int (in practice however, the chances of this are small, so the result of hashStableName makes a good hash key).

Makes a StableName for an arbitrary object. The object passed as the first argument is not evaluated by makeStableName.

The name of the constructor

The name of the datatype (unqualified)

The fully-qualified name of the module where the type is declared

The package name of the module where the type is declared