On 2008-11-26, Xah Lee <[EMAIL PROTECTED]> wrote:
comp.lang.lisp,comp.lang.functional,comp.lang.perl.misc,comp.lang.python,comp.lang.java.programmer
2008-11-25
Recently, Steve Yegge implemented Javascript in Emacs lisp, and
compared the 2 languages.
http://steve-yegge.blogspot.com/
http://code.google.com/p/ejacs/
One of his point is about emacs lisp's lack of namespace.
Btw, there's a question i have about namespace that always puzzled me.
In many languages, they don't have namespace and is often a well known
sour point for the lang. For example, Scheme has this problem up till
R6RS last year.
Scheme hasn't officially supported breaking a program into multiple files until
R6RS. If the language is defined in terms of one translation unit, it doesn't
make sense to have a namespace feature.
PHP didn't have namespace for the past decade till
about this year. Javascript, which i only have working expertise,
didn't have namespace as he mentioned in his blog.
Javascript programs are scanned at the character level by the browser as part
of loading a page. So there are severe practical limitations on how large
Javascript programs can be.
Namespaces are useful only in very large programs.
Elisp doesn't have
name space and it is a well known major issue.
C doesn't have namespaces, and yet you have projects like the Linux kernel
which get by without this.
Given that the Linux kernel can do without namespaces, it's easy to see how
Javascript and Elisp can survive without it.
Of languages that do have namespace that i have at least working
expertise: Mathematica, Perl, Python, Java. Knowing these langs
sufficiently well, i do not see anything special about namespace. The
_essence_ of namespace is that a char is choosen as a separator, and
the compiler just use this char to split/connect identifiers.
The essence of a true namespace or package system or whatever is that you can
establish situations in which you use the unqualified names.
You can emulate namespaces by adding prefixes to identifiers, which is
how people get by in C.
In C, you can even get the functionality of short names using the preprocessor.
I have done this before (but only once). In a widely-used public header file, I
prefixed all of the names of struct members (because struct members are not
immune to clashes: they clash with preprocessor symbols!)
struct foo {
int foo_category;
time_t foo_timestamp;
/* ... */
}
Inside the implementation module, I made macros for myself:
#define category foo_category
#define timestamp foo_timestamp
In this way, I didn't have to edit any of the code in order to move the struct
members into the namespace. Expressions like ``pf->category'' continued to work
as before.
Although i have close to zero knowledge about compiler or parser, but
from a math point of view and my own 18 years of programing
experience, i cannot fathom what could possibly be difficult of
introducing or implementing a namespace mechanism into a language.
The same things that make it difficult to add anything to a language, namely
the stupid way in which languages are designed to get in the way of extension.
What would it take to add namespaces to C, for instance?
If you have any proposal for a new C feature, the ISO C people encourage you to
develop a proof-of-concept, which means: hack it into an existing
implementation to demonstrate that it's feasible.
If you need new syntax, hacking it into an implementation means hacking it into
the parser. Everyone who wants to experiment with your feature needs to get
your compiler patches (for GCC for instance) and rebuild the compiler.
The process is painful enough that it's only worth doing if it solves something
that is perceived as being a critical issue.
do not understand, why so many languages that lacks so much needed
namespace for so long? If it is a social problem, i don't imagine they
would last so long. It must be some technical issue?
I recently read about a very useful theory which explains why technologies
succeed or fail.
See:
http://arcfn.com/2008/07/why-your-favorite-programming-language-is-unpopular.html
