World: r3wp

Comparison of BUILD and REDUCE/ONLY:

1) REDUCE/ONLY does not allow you to specify which words to evaluate, 
which would be safer, it rather specify which words to *not* evaluate
2) REDUCE/ONLY isn't /DEEP, i.e. it does not process subblocks
3) The evaluated words are local for BUILD

http://www.fm.tul.cz/~ladislav/rebol/build.r

(How many users would use BUILD?)

would that mean:

>> build [1 [3 + 2 now]]
== [1 [5 13-Oct-2006/11:16:56+2:00]]

?

because that's the kind of build I would be interested in

hmm... no it wouldn't. :-(

I don't have anything against BUILD, but I need to be convinced more 
on the practical uses, because I can't see how this makes block building 
any easier. Perhaps some more examples would be good. :-)

Examples contrasting compose (with /only and /deep) and reduce/only, 
would be great. I know it has a couple in the script. I've looked 
at it in the past, but haven't been driven to add it as a standard 
part of my process yet.

Henrik: Build can do it using one of the following ways:

    build [1 [ins 3 + 2 ins now]]
    build [1 only reduce [3 + 2 now]]
    build/with [1 inner] [inner: reduce [3 + 2 now]]


OTOH, your example is quite specific and not very general (I would 
say that it as a task for REDUCE/DEEP)

(except for the fact, that REDUCE does not have a /deep refinement)

I think some practical examples are needed, for example in building 
some HTML for a webpage. Something that shows that BUILD is significantly 
easier than a combination of REDUCE and COMPOSE.

building some HTML for a webpage
 - BUILD builds blocks not HTML

ok, a layout block then?

the example Mike liked is:

    view layout build/with [
        box 600x600 effect [
            draw [
                spider [
                    size 600x600
                    ; offset 100x100
                    pen black
                    scale 4
                    ; scale [0 150 300 450 600]
                    categories [

                        "Category 1" "Category 2" "Category 3" "Category 4"

                        "Category 5" "Category 6" "Category 7" "Category 8"
                    ]
                    directions
                    pen red
                    data [100 200 300 400 500 600 700 800]
                    pen blue
                    data [100 100 100 100 100 100 100 100]
                ]
            ]
        ]
    ] [spider: :spider*]

(it builds a DRAW block creating a Spider graph)

** Script Error: spider* has no value
** Where: build
** Near: spider: :spider*

Spider is: http://www.fm.tul.cz/~ladislav/rebol/spider.r

>> do http://www.fm.tul.cz/~ladislav/rebol/spider.r
connecting to: www.fm.tul.cz
Script: "Spider" (8-Sep-2006/16:40:58+2:00)
** Script Error: lfunc has no value
** Near: spider*: lfunc [
    [catch] 

    description [block!] "a block containing a description of a chart"
] [] [
    current-...
>>

use INCLUDE as follows:

do http://www.fm.tul.cz/~ladislav/rebol/include.r
append include-path http://www.fm.tul.cz/~ladislav/rebol/
include %spider.r

it wants to find the file in my local cache before the remote one 
and crashes:

>> do http://www.fm.tul.cz/~ladislav/rebol/include.r
connecting to: www.fm.tul.cz
Script: "Include" (5-Jan-2006/14:31:42+1:00)
>> append include-path http://www.fm.tul.cz/~ladislav/rebol/
== [%. %/Volumes/c/rebol/ http://www.fm.tul.cz/~ladislav/rebol/]
>> include %spider.r
connecting to: www.fm.tul.cz
** Access Error: Cannot open /Volumes/c/rebol/spider.r
** Where: include-script
** Near: found: load/all target 
if header
>>

Sorry, if I'm being a little difficult :-)

no problem, checking what went wrong in your case

>> what-dir
== %/Volumes/c/rebol/

if that helps.

OK, give me a few minutes to check the versions

aha, this looks like a result of the last INCLUDE change. It is surprising, 
that nobody noticed it yet.

Henrik: could you please test again?

(INCLUDE bug corrected)

same error

I can see that the script dates for include.r are different, so it 
must be the new version

ah... a fresh console helped.

yes, INCLUDE does not reload itself when already defined

back to the example: what exactly does Spider do? I don't think it's 
very clear from the example what's going on. there could be hundreds 
of lines of code hidden there.

you need to have a look at http://www.fm.tul.cz/~ladislav/rebol/spider.r
. It generates the spider graph as you could see, if you succeeded 
to run the code

Henrik: could you please do one more test - I updated INCLUDE once 
again

I saw it. The draw block would then be evaluated from the spider 
code and then inserted at that place?

include still works fine in a fresh console

yes, you can see the result of it if you do:

probe build/with [
        box 600x600 effect [
            draw [
                spider [
                    size 600x600
                    ; offset 100x100
                    pen black
                    scale 4
                    ; scale [0 150 300 450 600]
                    categories [

                        "Category 1" "Category 2" "Category 3" "Category 4"

                        "Category 5" "Category 6" "Category 7" "Category 8"
                    ]
                    directions
                    pen red
                    data [100 200 300 400 500 600 700 800]
                    pen blue
                    data [100 100 100 100 100 100 100 100]
                ]
            ]
        ]
    ] [spider: :spider*]

I guess I'm just really hard to impress today. I need a much sexier 
example to be convinced of the raw power of BUILD. :-)

:-)

something like "this takes 100 lines of code to do with regular REBOL 
block construction functions, while BUILD can do it in 20 and make 
much prettier code out of it"

I have got a similar XYPLOT function creating an XY graph, although 
I did not release it yet

Well, how would you do the

view layout build/with [
        box 600x600 effect [
            draw [
                spider [
                    size 600x600
                    ; offset 100x100
                    pen black
                    scale 4
                    ; scale [0 150 300 450 600]
                    categories [

                        "Category 1" "Category 2" "Category 3" "Category 4"

                        "Category 5" "Category 6" "Category 7" "Category 8"
                    ]
                    directions
                    pen red
                    data [100 200 300 400 500 600 700 800]
                    pen blue
                    data [100 100 100 100 100 100 100 100]
                ]
            ]
        ]
    ] [spider: :spider*]

example without using BUILD?

Ladislav - will build be part of R3? :-)

That is why I am asking here - if there are users who will be using 
it

by looking at it, SPIDER looks like a regular function to me with 
the following block as input. I guess it can't be, because then the 
layout block could simply be done by enclosing spider [...] in ()'s 
and compose/deep the whole thing.

compose/deep - actually it could be used in this case, because I 
didn't use parens anywhere

well, just getting rid of ()'s isn't enough for me. I would want 
significant code reduction in cases where blocks would be cumbersome 
to build.

this is not about getting rid of parens, this is about *not clashing 
with parens*

With COMPOSE/DEEP you cannot use parens safely

by safely you mean selective evaluation?

yes