return index of array within an array (or List... in this case)
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return index of array within an array (or List... in this case)
by scacinto
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j = List[[0,2,3], [4,2,0], [3,0,4]];
j.at(2) // this works fine -- returns the array [3,0,4] j.indexOf([3,0,4]); // this returns 'nil' j.includes([3,0,4]); // also returns 'nil' is there some 'majicke' I can work on this list to return the index of the array or at least answer true? thanx S |
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Re: return index of array within an array (or List... in this case)
by James Harkins-2
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It's important to understand why 'includes' doesn't work in this case. It's the difference between equality and identity. // execute each line separately a = [3, 0, 4]; b = [3, 0, 4]; // equality test a == b --> true // identity test a === b --> false And the cruncher... a.dump; b.dump; Instance of Array { (0E6DED00, gc=40, fmt=01, flg=00, set=02) indexed slots [3] 0 : Integer 3 1 : Integer 0 2 : Integer 4 } Instance of Array { (0D5FD350, gc=40, fmt=01, flg=00, set=02) indexed slots [3] 0 : Integer 3 1 : Integer 0 2 : Integer 4 } Note that the memory addresses are different - 0E6DED00 vs 0D5FD350. Since they live at different places, they can't be the same object, and the identity test is true only if they are exactly the same object (not different instances of the same class with the same contents). 'Includes' tests for identity, not equality. If you're using my library, you can use includesEqual which uses an equality test and will give you the results you want. hjh On Jun 30, 2008, at 9:48 PM, scacinto wrote:
: H. James Harkins : http://www.dewdrop-world.net .::!:.:.......:.::........:..!.::.::...:..:...:.:.:.:..: "Come said the Muse, Sing me a song no poet has yet chanted, Sing me the universal." -- Whitman |
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Re: return index of array within an array (or List... in this case)
by scacinto
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Good to know, thank you. Using my deductive reasoning skills, I'll assume that indexOf also tests for identity and not equality. Is there a general rule for, or way of finding out, what tests for which?
Thanks again. -S
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Re: return index of array within an array (or List... in this case)
by Dan Stowell
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James mentioned "includesEqual" which is in his library. If you want a
solution that works on pure unadulterated SC, then note that the "indexOfEqual" method is built-in and does the equivalent thing for indexOf. j = List[[0,2,3], [4,2,0], [3,0,4]]; j.indexOfEqual([3,0,4]); // Finds it! j.indexOfEqual([3,0,4]).notNil; // this does the same thing as 'includesEqual' >Is there a general > rule for, or way of finding out, what tests for which? Good question. I don't know if I can state a general rule; but to find out, look at the definition of the method. Highlight the word "indexOf" in SC and press Cmd-Y. You'll get a list appearing, of different classes' implementations. Out of those, highlight "SequenceableCollection:indexOf" and press Cmd-Y. You'll see the method's implementation, which uses a loop and a test of identity (the triple equals sign, ===). It can be a bit strange at first, trying to un-pick the source code in this way, but it's often helpful. Dan 2008/7/1 scacinto <scottpetersen@...>: > > Good to know, thank you. Using my deductive reasoning skills, I'll assume > that indexOf also tests for identity and not equality. Is there a general > rule for, or way of finding out, what tests for which? > > Thanks again. > > -S > > > > > James Harkins-2 wrote: >> >> It's important to understand why 'includes' doesn't work in this >> case. It's the difference between equality and identity. >> >> // execute each line separately >> >> a = [3, 0, 4]; >> >> b = [3, 0, 4]; >> >> // equality test >> a == b >> --> true >> >> // identity test >> a === b >> --> false >> >> And the cruncher... >> >> a.dump; b.dump; >> >> Instance of Array { (0E6DED00, gc=40, fmt=01, flg=00, set=02) >> indexed slots [3] >> 0 : Integer 3 >> 1 : Integer 0 >> 2 : Integer 4 >> } >> Instance of Array { (0D5FD350, gc=40, fmt=01, flg=00, set=02) >> indexed slots [3] >> 0 : Integer 3 >> 1 : Integer 0 >> 2 : Integer 4 >> } >> >> Note that the memory addresses are different - 0E6DED00 vs 0D5FD350. >> Since they live at different places, they can't be the same object, >> and the identity test is true only if they are exactly the same >> object (not different instances of the same class with the same >> contents). >> >> 'Includes' tests for identity, not equality. >> >> If you're using my library, you can use includesEqual which uses an >> equality test and will give you the results you want. >> >> hjh >> >> >> >> On Jun 30, 2008, at 9:48 PM, scacinto wrote: >> >>> >>> j = List[[0,2,3], [4,2,0], [3,0,4]]; >>> j.at(2) // this works fine -- returns the array >>> [3,0,4] >>> >>> j.indexOf([3,0,4]); // this returns 'nil' >>> j.includes([3,0,4]); // also returns 'nil' >>> >>> is there some 'majicke' I can work on this list to return the index >>> of the >>> array or at least answer true? >> >> >> : H. James Harkins >> : jamshark70@... >> : http://www.dewdrop-world.net >> .::!:.:.......:.::........:..!.::.::...:..:...:.:.:.:..: >> >> "Come said the Muse, >> Sing me a song no poet has yet chanted, >> Sing me the universal." -- Whitman >> >> >> > > -- > View this message in context: http://www.nabble.com/return-index-of-array-within-an-array-%28or-List...-in-this-case%29-tp18207750p18208771.html > Sent from the Supercollider - User mailing list archive at Nabble.com. > > > _______________________________________________ > sc-users mailing list > > > info (subscribe and unsubscribe): http://swiki.hfbk-hamburg.de:8888/MusicTechnology/880 > archive: http://www.listarc.bham.ac.uk/marchives/sc-users/ > search: http://www.listarc.bham.ac.uk/lists/sc-users/search/ > -- http://www.mcld.co.uk _______________________________________________ sc-users mailing list info (subscribe and unsubscribe): http://swiki.hfbk-hamburg.de:8888/MusicTechnology/880 archive: http://www.listarc.bham.ac.uk/marchives/sc-users/ search: http://www.listarc.bham.ac.uk/lists/sc-users/search/ |
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Re: return index of array within an array (or List... in this case)
by scacinto
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Indeed, yes! Thanks Dan. I did a search for methods with "Equal" in them and discovered these, much to my satisfaction. Checking for the '===' is a great idea, as well. The reason for my general rule was to see if there was a quick and dirty was of establishing identity. It seems that any integer is simply an integer -- returns an integer, etc. so there's no way of telling one from another. At the same, a = 'a' and b = 'a' are equivalent but a = "a" and b = "a" are not. Of course, the string has indexed slots as the array does, and so is identifiable by its memory allocation number thingy -- and the same for functions.
Thnks for your post S
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