[KickAssClown]

Are there any computer languages that have primitives, or objects which contain not a value, or address, but a expression of the written language itself?

Perhaps I am just having difficulty conceiving of the mechanism of doing this with languages I use.

[pgrmdave]

I don't know of any, but look into LISP, and read Godel Escher Bach and/or Metamagical Themus by Douglas Hofstader - if you want to learn about self-reference, whether in mathematics, computers, or language, those two books will provide excellent resources.

[KickAssClown]

Actually, I thought of this in reference to GEB, which I am in the process of reading.

I had been thinking of self-referential languages for the longest time. I just recently have been working on the capability to express my thoughts in this field.

[TheFaithfulStone]

My all time favorite example of self-reference.

Good url. Will be posted again later.

TFS

[CraigD]

Originally Posted by KickAssClown

Are there any computer languages that have primitives, or objects which contain not a value, or address, but a expression of the written language itself?

Some languages – especially interpreted (as opposed to compiled) one lend themselves better to what I thing you’re describing.

Though LISP is usually mentioned as a language that lends itself to containing expressions of itself, I’m fond of MUMPS (as anyone who’s noted the programs I’ve posted at hypography is likely aware ), which also lends itself to manipulating its own code.

Here’s a very simple example, cut from a MUMPS direct (interactive) mode terminal session (note the “USER>” is a typical direct mode prompt, not actual input or program output):

USER>r X
w 1 q:'5  s $p(X," ",3)="q:'"_($p(X,"'",2)-1) x X w 2
USER>x X
11111122222
USER>w X
w 1 q:'0  s $p(X," ",3)="q:'"_($p(X,"'",2)-1) x X w 2
USER>

This program counts down from 5 to 0. It’s not a particularly good or clever program, but remarkable in that the code contained in symbol X references no symbol but itself. Note that MUMPS keywords can be and usually are abbreviated (eg: r[ead] w[rite] q[uit] s[et] $p[iece] x[ecute]), leading many to comment that it looks like line noise.

It’s fairly easy to write much more complicated and meaningful self modifying MUMPS programs, such as in the puzzle game-playing program in my post ”Self modifying code in an interpreted language”.

[moo]

One way of doing this (in any language) is have your app write a simple "pseudo" language to a file, then code a simple interpreter to read it. I played around with something like this a few years ago for experimenting with self modifying AI programs. You could use RAM, but a file holds the data for review even if the app crashes.

moo

[TheFaithfulStone]

So Clown, I found this on Wikipedia, are you talking about a quine?

TFS

[alexander]

you can do it with PHP man. Check out the eval function