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5.6 Local Call

Python supports two kinds of function call: full call and local call. Full call is the standard calling convention; its late binding and generality make Common Lisp what it is, but create unavoidable overheads. When the compiler can compile the calling function and the called function simultaneously, it can use local call to avoid some of the overhead of full call. Local call is really a collection of compilation strategies. If some aspect of call overhead is not needed in a particular local call, then it can be omitted. In some cases, local call can be totally free. Local call provides two main advantages to the user:

• Local call makes the use of the lexical function binding forms flet and labels much more efficient. A local call is always faster than a full call, and in many cases is much faster.
• Local call is a natural approach to block compilation, a compilation technique that resolves function references at compile time. Block compilation speeds function call, but increases compilation times and prevents function redefinition.

• Self-Recursive Calls
• Let Calls
• Closures
• Local Tail Recursion
• Return Values