Thursday, May 1, 2008

import, package and namespace - python, c++, java and perl

Namespace is a common challenge, and a common feature. Physically, module files invariably live in a hierarchical file system.

Perl's solution revolves around the concept of package and symbol table....

java's solution is rooted in fully qualified type names. Every named type has a FQTN. They naturally form a hierarchical namespace tree.
--c#???
--Python
Python instantiates a namespace object "os" (or sys, re) when you say "import os, sys, re", so you can use the dot notation like os.path. Thanks to this "object", Python's introspection, instrumentation and meta programming capabilities shine through.

Python's "from os import environ" imports the environ variable into the current namespace, just like c++ "using std::out"

--C++ namespaces are well-covered in [[absolute c++]], and also concisely covered in effC++
using namespace std; // imports all the vars and funcs into "here" so we don't need to say std::cout
using std::cout; // imports just one var

However, in both cases your own "cout" variable will clash with the cout imported.

There's a 3rd usage of "using myBaseClass::method2" on P413 of ARM

Note, "using" can be nested in  a class.

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