[REBOL] Re: En Masse block operations
Hi, Tim, Tim Johnson wrote: Hello All: I would like to apply the same operation to all members of a nested block. ;Example: blk: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] blk: do-all blk next ; set all members to next element ;result sought: [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] Sounds like a job for MAP to me... blk: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] ... then ... map: function [[catch] b [block!] f [function!] /all] [r v] [ r: make block! length? b foreach c b [ if any [found? v: do [f c] all] [append/only r v] ] r ] ... and, finally ... map blk func [s][next s] == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] ... or ... x: map blk func [s] [next s] == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] x: map x func [s] [next s] == [[3 4] [7 8] [11 12] [15 16 17] e] map x func [s] [head s] == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] HTH! -jn- -- This sentence contradicts itself -- no actually it doesn't. -- Doug Hofstadter joeldotneelyatfedexdotcom -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes.
[REBOL] Re: En Masse block operations
Hi Tim, I think map will do what you want. ; Larry Palmiter's version but Ladislav and Andrew also have them map: func [fn blk args /local result][ result: copy [] repeat el blk [append/only result fn :el args] return result ] test: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] map :next test none == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] map :head test none == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] --Gregg -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes.
[REBOL] Re: En Masse block operations
Dont use 'foreach. 'Foreach makes a copy of the value, bungling your method. Use 'forall or 'repeat. I like using 'repeat for this sort of thing because I can do it without the awkward [block: head block] at the end. Also you might want to use 'block? instead of 'series? to validate whether an operation is warranted. Many other data values are considered a series... series? abc == true series? ftp://bob.jones.com == true series? [EMAIL PROTECTED] == true --Ryan Tim Johnson wrote: Hello All: I would like to apply the same operation to all members of a nested block. ;Example: blk: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] blk: do-all blk next ; set all members to next element ;result sought: [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] blk: do-all blk head ; set all members to head ; result sought: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] ; I've started by this simple function, which is not doing just ; what I want: REBOL[] do-all: func[blk[block!] ][ ;cmd[word!] foreach member blk[ if series? member[ member: next member print mold member ] ] blk ] test: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] print mold do-all test ;and I get do %sample.r Script: Untitled (none) [2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] TIA -- Tim Johnson [EMAIL PROTECTED] http://www.johnsons-web.com -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes. -- Ryan Cole Programmer Analyst www.iesco-dms.com 707-468-5400 -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes.
[REBOL] Re: En Masse block operations
On Tue, Oct 16, 2001 at 11:18:05AM -0600, Gregg Irwin wrote: Hi Tim, I think map will do what you want. Yes indeed. It's exactly what I want. :) ==I note a bonus: I think I'm seeing how one passes a function as an argument. Thank you Gregg ; Larry Palmiter's version but Ladislav and Andrew also have them map: func [fn blk args /local result][ result: copy [] repeat el blk [append/only result fn :el args] return result ] test: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] map :next test none == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] map :head test none == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] --Gregg -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes. -- Tim Johnson [EMAIL PROTECTED] http://www.johnsons-web.com -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes.
[REBOL] Re: En Masse block operations
Hi Tim, by now you've heard about map more than once, one other possibility would be, e.g. Once upon a time Tim Johnson spoketh thus: Hello All: I would like to apply the same operation to all members of a nested block. ;Example: blk: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] blk: do-all blk next ; set all members to next element ;result sought: [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] blk: do-all blk head ; set all members to head ; result sought: [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] forall blk [if block? blk/1 [ blk/1: next blk/1 ]] == [] blk: head blk == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] one] forall blk [if block? blk/1 [ blk/1: head blk/1 ]] blk: head blk == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] kind regards, Ingo -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes.
[REBOL] Re: En Masse block operations/foreach bug?
On Tue, Oct 16, 2001 at 02:09:26PM -0500, Joel Neely wrote: Hi, Tim, Tim Johnson wrote: I see Ryan's opinion not to use 'foreach. Could you comment on his opinion on this. (I've seen references to a foreach bug and I almost never use it myself.) AFAIK there's no bug involved, but it is possible to misunderstand what FOREACH (and REPEAT, for that matter) are doing. Here's your original sample block: ==If memory serves me well (always this disclaimer on my part)... There was a discussion on this list some months ago regarding a bug in 'foreach. In that discussion was a link to a file called bugfixes.r I have downloaded that file, it makes references to several bugs which it claims to fix. I haven't done anything with that code myself. ==I actually haven't found any problems myself with either 'repeat or 'foreach. ==There's a lot of good stuff here Joel, I'm about to start playing with it. You should be doing training in rebol. Seriously. thanks tj blk == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] Let's go through it with FOREACH... foreach item blk [print item: next item] 2 3 4 6 7 8 10 11 12 14 15 16 17 ne ... and then look at the block again ... blk == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] The block itself is unchanged. The (local) word ITEM was set to each value in the block in turn. This means that the expression item: next item in the above code is changing the position to which ITEM refers, but not changing the (explicit, literal) series reference that is in each position of BLK. The same thing happens if you use REPEAT as follows: repeat item blk [print item: next item] 2 3 4 6 7 8 10 11 12 14 15 16 17 ne blk == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] The point is that if you want to mutate the values in BLK, you're going to have to do one of two things: 1) work directly with the references in BLK (or an alternate reference to BLK), or 2) compute a new block based on the old values in BLK and set BLK to refer to that new block. The first alternative could be written as forall blk [ blk/1: next blk/1 ] blk: head blk == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] blk == [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] and could be undone by forall blk [blk/1: head blk/1] blk: head blk == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] The second alternative could be coded in-line or done via MAP, as discussed in my prior email. loop 5 [print mold blk: map blk func [s] [next s]] [[2 3 4] [6 7 8] [10 11 12] [14 15 16 17] ne] [[3 4] [7 8] [11 12] [15 16 17] e] [[4] [8] [12] [16 17] ] [[] [] [] [17] ] [[] [] [] [] ] blk: map blk func [s] [head s] == [[1 2 3 4] [5 6 7 8] [9 10 11 12] [13 14 15 16 17] one] In any event, I'm not aware of a FOREACH bug and use it all the time. HTH! -jn- -- This sentence contradicts itself -- no actually it doesn't. -- Doug Hofstadter joeldotneelyatfedexdotcom -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes. -- Tim Johnson [EMAIL PROTECTED] http://www.johnsons-web.com -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with unsubscribe in the subject, without the quotes.
