>>>>Search String: "I like (parens) and the Apple ][+" they said.
(above quote from the posted question). Yary, you could have written that! --B. On Mon, Sep 20, 2021 at 7:53 AM yary <not....@gmail.com> wrote: > > See Challenge #2 in > https://theweeklychallenge.org/blog/perl-weekly-challenge-131/ ... ! > > -y > > > On Wed, Aug 25, 2021 at 2:08 PM William Michels <w...@caa.columbia.edu> wrote: >> >> Hi Andy! >> >> Maybe this helps (separate coding elements with parens and/or brackets, >> still get the same result): >> >> > say 1, 1, * + * ...^ *>= 100; >> (1 1 2 3 5 8 13 21 34 55 89) >> >> > say 1, 1, * + * ...^ (*>= 100); >> (1 1 2 3 5 8 13 21 34 55 89) >> >> > say 1, 1, * + * ...^ ( * >= 100); >> (1 1 2 3 5 8 13 21 34 55 89) >> >> > say (1, 1, * + *) ...^ ( * >= 100); >> (1 1 2 3 5 8 13 21 34 55 89) >> >> > say 1, 1, * + * [...^] ( * >= 100); >> (1 1 2 3 5 8 13 21 34 55 89) >> >> > say (1, 1, * + *) [...^] ( * >= 100); >> (1 1 2 3 5 8 13 21 34 55 89) >> >> From Yary: >> >> Ranges also support arbitrary functions, the doc page shows a Fibonacci >> >> number generator >> >> https://docs.raku.org/language/operators#index-entry-sequence_operator >> >> The Fibonacci code above (and in the docs) uses the sequence operator (infix >> ...), not the range operator (infix ..). To recap for Andy: Yary, Vadim, >> Brian, Fernando and Marc have posted code using the sequence operator; I've >> previously posted code using the range operator coupled with a grep() call >> [I recall reading somewhere that ranges are cheaper to construct than >> sequences, but can't locate the reference at the moment]. >> >> FWIW_1, I was unable to get the Fibonacci code to work with the range >> operator: >> >> > say 1, 1, * + * ..^ *>= 100; >> 11WhateverCode.new >> >> FWIW_2, I've had good luck grepping out composite sequences with the >> 'range_operator / grep' strategy: >> >> > #Using "(^*)" as a synonym for the range "(0..*-1)", see: >> > https://docs.raku.org/type/Range >> Nil >> >> > ( 0..11 ).[ (^*).grep: * %% 2 ] >> (0 2 4 6 8 10) >> >> > ( 0..11 ).[ (^*).grep: * %% 3 ] >> (0 3 6 9) >> >> > ( 0..11 ).[ (^*).grep: * %% (2|3) ] >> (0 2 3 4 6 8 9 10) >> >> > ( 0..11 ).[ (^*).grep: * %% any(2,3) ] >> (0 2 3 4 6 8 9 10) >> >> HTH, Bill. >> >> PS Now to try to understand the differences (shown earlier in this thread) >> when the := binding operator is used! >> >> >> On Wed, Aug 25, 2021 at 7:15 AM Andy Bach <andy_b...@wiwb.uscourts.gov> >> wrote: >>> >>> I "misread" >>> say 1, 1, * + * ...^ *>= 100; >>> >>> thinking "shouldn't it be '<=' as you want the total to be less than 100?" >>> but >>> $ raku -e 'say 1, 1, * + * ...^ *<= 100;' >>> ===SORRY!=== Error while compiling -e >>> Whitespace required before <= operator >>> at -e:1 >>> ------> say 1, 1, * + * ...^ *<= 100;⏏<EOL> >>> expecting any of: >>> postfix >>> >>> and >>> $ raku -e 'say 1, 1, * + * ...^ * <= 100;' >>> () >>> $ raku -e 'say 1, 1, * + * ...^ * >= 100;' >>> (1 1 2 3 5 8 13 21 34 55 89) >>> >>> So, then it dawned on me that the '>=' is "binding" (right word?) to the >>> "*" marking the end of the sequence as "until I am ge 100". Though that >>> doesn't quite work, >>> $ raku -e 'say 1, 1, * + * ...^ * <= 100;' >>> () >>> >>> Ah, I see, it does work. The end of the sequence is the first number less >>> than 100, so 1 succeeds. I guess the sequence never gets started. >>> ________________________________ >>> From: yary <not....@gmail.com> >>> Sent: Tuesday, August 24, 2021 8:39 PM >>> To: William Michels <w...@caa.columbia.edu> >>> Cc: Marc Chantreux <e...@phear.org>; raku-users <perl6-us...@perl.org> >>> Subject: Re: [better solution] pairs of separators from a string >>> >>> CAUTION - EXTERNAL: >>> >>> Hi Bill, >>> >>> When building a range that's an arithmetic or geometric progression, the >>> sequence operator is a little quicker to type. And thus also more likely to >>> be understood more quickly too. >>> >>> > ('a' .. 'h')[(0..*-1).grep: * %% 2 ] >>> (a c e g) >>> > ('a' .. 'h')[ 0, 2 ... * ] >>> (a c e g) >>> >>> > ('a' .. 'h')[(0..*-1).grep: * % 2 ] >>> (b d f h) >>> > ('a' .. 'h')[1, 3...*] >>> (b d f h) >>> >>> # Geometric example- powers of 2 >>> > ('a' .. 'z')[1, 2, 4...*] >>> (b c e i q) >>> >>> There isn't a simple translation for the is-prime example that I can think >>> of, that is a good use for "grep" >>> >>> Ranges also support arbitrary functions, the doc page shows a Fibonacci >>> number generator >>> https://docs.raku.org/language/operators#index-entry-sequence_operator >>> "This allows you to write >>> >>> say 1, 1, * + * ...^ *>= 100; >>> # OUTPUT: «(1 1 2 3 5 8 13 21 34 55 89)» >>> >>> to generate all Fibonacci numbers up to but excluding 100." >>> >>> >>> >>> >>> -y >>> >>> >>> On Tue, Aug 24, 2021 at 6:36 PM William Michels via perl6-users >>> <perl6-us...@perl.org> wrote: >>> >>> Hi Marc, >>> >>> My understanding is that ranges are pretty cheap to construct, and in any >>> case, the range @x[0..*-1] is just the index of all elements in @x. The >>> .grep() approach may be most useful if you have a function (e.g. %, %%, and >>> .is-prime shown below): >>> >>> > (0...9) >>> (0 1 2 3 4 5 6 7 8 9) >>> > (0...9)[0..*-1] >>> (0 1 2 3 4 5 6 7 8 9) >>> > (0...9)[(0..*-1).grep: * ] >>> (0 1 2 3 4 5 6 7 8 9) >>> > (0...9)[(0..*-1).grep: * %% 2 ] >>> (0 2 4 6 8) >>> > (0...9)[(0..*-1).grep: * % 2 ] >>> (1 3 5 7 9) >>> > (0...9)[(0..*-1).grep: *.is-prime ] >>> (2 3 5 7) >>> > >>> >>> You can find a related example in the docs ( >>> https://docs.raku.org/routine/grep#class_HyperSeq). Anyway, I'm sure each >>> approach has its fans, >>> >>> Best, Bill. >>> >>> On Tue, Aug 24, 2021 at 3:59 AM Marc Chantreux <e...@phear.org> wrote: >>> >>> hello everyone, >>> >>> I made a mistake while replying to all of us so anwsers never reached >>> your boxes. I'll summerize in one answer: >>> >>> Bill: >>> >>> > Is it just even/odd elements that you want to separate out? If so, maybe >>> > .grep() is your friend here >>> >>> I don't think it is: 0, 2 ... * seems to be >>> >>> * closer to what i have in mind when i think about the problem >>> (so i invoke readability there) >>> * probably more efficient than (0..*).grep(* % 2) that >>> * generate twice the number of required elements >>> * need to filter the result >>> >>> Also, trying to play with this version: >>> >>> my ($a,$b) = >>> .[0,2...*], >>> .[1,3...*] >>> with <AaBbCc>.comb; >>> >>> just don't work because the lists are squashed into scalar context >>> in the process. >>> >>> So Brian and Fernando made my day with := and the unexpected power of >>> the [] operator. >>> >>> my (@a,@b) := <AaBbCc>.comb[ [0,2...*], [1,3...*] ]; >>> >>> I really like how declarative it is. Also the use of := now seems >>> obvious to me. >>> >>> Sigils still remains something strange to me desprite all your examples >>> but i'll take some time. thanks everyone. >>> >>> marc >>> >>> CAUTION - EXTERNAL EMAIL: This email originated outside the Judiciary. >>> Exercise caution when opening attachments or clicking on links. >>>
