Re: why learn C?

[jayessay <nospam@foo.com>]

Markus E Leypold <development-2006-8ecbb5cc8aREMOVETHIS@ANDTHATm-e-leypold.de> writes:

> translators to their favorite target language. Then you post reminded
> me that the Lisp macros are quit succesfull and don't seem to be the
> problem I always experienced with macro languages.

The primary thing to realize here about this point is that Lisp
"macros" are not anything like the typical notion of macros from
pretty much any<where/thing> else.  They are not text substituters or
code templates, or code parameterizers, etc.  They are functions
which, like any other function, can make use of the entire language
(including the compiler and evaluator - which are part of the language
definition), any libs, external environment (databases, distributed
objects (via corba or other IDL/sockets), whatever), etc.

The difference is that they are 1) called at a special time (macro
expansion time - which most typically occurs during compile time), 2)
they are invoked with their arguments _un_evaluated (this is a big
part of why they can be so useful in creating new language level
constructs), and 3) they can be passed the current lexical environment
(this last was not properly fleshed out in the ANSI spec, but Franz
has done a very nice job of doing that and providing the spec and
implementation to the community).

Because of this, things like external "preprocessing" become empty and
irrelevant concepts.  It also means you can build layered families of
seamlessly interconnected domain level languages.

> Still I have a bad feeling with macros: They are a really big
> temptation to misuse them.

I would substitute "possibility" for "really big temptation".  Just
like for unchecked conversion, goto, and OOP.  Of course, YMMV.


/Jon

-- 
'j' - a n t h o n y at romeo/charley/november com