On Wed, 02 Mar 2011 08:45:43 -0500, Jason E. Aten <[email protected]>
wrote:
I find this an interesting discussion. Coming from writing alot of code
in
language that makes extensive and
highly effective use of named arguments (R), I can say that optional
named
arguments
(as in Lisp, and descendants like Python and R) do have big software
engineering benefits,
but also come with a substantial costs in terms of complexity of the
function call sequence.
That is, named arguments can be expensive in a typical interpreted
implementation
(probably one reason why R and Python are much slower to execute than the
other
interpreted languages), presumably because each function call has to
invoke hash
table lookups to determine the canonical formal position of each actual
argument, and deal with variadic
cases, to rearrange the order of the arguments to match expectations of
the
callee.
Someone familiar with lisp compilers could probably tell you if the heavy
speed tax is intrinsic
or just the price of interpretation.
It would indeed be an interesting challenge to see if the compile-time
metaprogramming
features of D would allow one to include named arguments in an opt-in
fashion without speed reduction.
Considering that calling a function with parameters by name directly
translates at compile time to a function call by position, there should be
zero speed impact. The interpretation of the parameter names, which is
done at runtime for Python, would be done at compile time in D.
-Steve
