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From: kjell@ygdrasil.ucsc.edu (Kjell E Post)
Newsgroups: comp.lang.apl
Subject: Forks, Hooks and With in J
Keywords: fork, hook, J
Message-ID: <kjell.675944273@ygdrasil>
Date: 3 Jun 91 10:17:53 GMT
Article-I.D.: ygdrasil.kjell.675944273
Sender: usenet@darkstar.ucsc.edu
Lines: 39

I've ordered the Tangible Math book and started to program in J, but find
the use of & (with) confusing, especially in conjunction with forks and hooks.

For instance, (0&,) and (,&0) seems to represent the trees

	  ,			,
	 / \		       / \
	0			  0

respectively.  Is there any reason why this notation was chosen, i.e.
what is the underlying functionality of '&'?  

I'm also curious about the expressibility of '&', fork, and hook.  
In particular, I'm interested in representing the following dag as a verb,
using only '&', '~', fork/hook, and the items in the dag.

           #
          / \
	+:   \
       /  \   \
      /     ,  \
     |     / \  \
     |   }.   1  |
     |    |      |
     `----=  	 |
	 / \	 |
	/   \	 |
       ,     \	 |
      /	\     \	/
     0	 +     ,
	/ \   / \
           1     0		<--- Note: the empty leaves represents
					   argument positions.

--
  |   |  |\  /| |\  |\   | Kjell Post               | Vi i Sverige har blivit
  |  /|\ | \/ | | \ | \  | CS Grad Student, UCSC    | trygghetsnarkomaner.
 /|\ \|/ |    | |   |    | email: kjell@cs.ucsc.edu | Livet best}r inte bara av
/ | \ |  |    | |   |    `--------------------------' trygghet.  --Curt Nicolin