Starting with index 1 is meaningful only in cases you're not doing any computation on the index value itself... but then you could start from 14 too without much problems either.
If the actual numeric value of the index is used for computations then you will find that in most cases the correct index for the first element is 0 (e.g. polynomial terms where the index is also used in exponent).
So when doesn't matter you can use 1 (or 2 or 42), but when it does you really need to use 0. Then why not using 0 always?
The number 0 was a great discovery, if you're teaching please don't cripple your students brain making them thinking in roman numerals, you're not helping them.
Hey Andrea! I appreciate the comment, but I don't find it overly constructive. Is it necessary to put my teaching abilities into question?
I made no mention of a preference for indexing by 1 anywhere in this article or the comments below. All I said was that my students struggle with the substring method in Java, and I tried to put myself in their shoes.
I'm not questioning your teaching abilities, but that apparently (from tone) you dislike the idea of indexing from 0.
This is unfortunately not uncommon (see the Lua language, for example) but the fact remains that indexing from 1 is a bad idea and EWD was right on this.
Sometimes it helps thinking to indexes as being "between" elements...
content H e l l o , W o r l d .
|___|___|___|___|___|___|___|___|___|___|___|___|___|
index 0 1 2 3 4 5 6 7 8 9 10 11 12 13
so the interval 3-5 is clearly "lo" and the number of elements included in the interval a, b is b - a.
This way of thinking simplifies a lot reasoning for example when implementing binary search or raster graphic algorithms.
This mental model is equivalent to [a, b[, but (maybe) easier to understand and remember.
x[i] is just the element between i and i+1.
Some API solve the problem of substring-like interfaces by relying on start/size instead of start/end (this is what Qt does in many cases, for example). Unfortunately the same Qt framework made the wrong choice of using "boundary-inclusive" intervals when implementing right() and bottom() method for integer rectangles, a poor choice that makes hard to write pixel-perfect code and force a lot of +1 and -1 in code: floating point rectangles are ok, and the mistake on the integer case is acknowledged in the documentation (but unfortunately cannot be removed because of backward compatibility reasons).
I thought you were asking for comments, so I commented.
I think the view that substring in Java has a "quirk" because uses the [a, b[ convention for intervals is questionable.
That "semi-open interval" is in my opinion the correct approach (may be on par or second only to a start/size approach). A "boundary included" [a, b] would instead be worse for many reasons.
Java has no "quirk" here: it's the correct thing to do (and please note that I'm surely NOT a Java fan, at all).
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Starting with index 1 is meaningful only in cases you're not doing any computation on the index value itself... but then you could start from 14 too without much problems either.
If the actual numeric value of the index is used for computations then you will find that in most cases the correct index for the first element is 0 (e.g. polynomial terms where the index is also used in exponent).
So when doesn't matter you can use 1 (or 2 or 42), but when it does you really need to use 0. Then why not using 0 always?
The number 0 was a great discovery, if you're teaching please don't cripple your students brain making them thinking in roman numerals, you're not helping them.
Hey Andrea! I appreciate the comment, but I don't find it overly constructive. Is it necessary to put my teaching abilities into question?
I made no mention of a preference for indexing by 1 anywhere in this article or the comments below. All I said was that my students struggle with the substring method in Java, and I tried to put myself in their shoes.
I'm not questioning your teaching abilities, but that apparently (from tone) you dislike the idea of indexing from 0.
This is unfortunately not uncommon (see the Lua language, for example) but the fact remains that indexing from 1 is a bad idea and EWD was right on this.
Sometimes it helps thinking to indexes as being "between" elements...
so the interval 3-5 is clearly "lo" and the number of elements included in the interval
a, bisb - a.This way of thinking simplifies a lot reasoning for example when implementing binary search or raster graphic algorithms.
This mental model is equivalent to
[a, b[, but (maybe) easier to understand and remember.x[i]is just the element betweeniandi+1.Some API solve the problem of
substring-like interfaces by relying onstart/sizeinstead ofstart/end(this is what Qt does in many cases, for example). Unfortunately the sameQtframework made the wrong choice of using "boundary-inclusive" intervals when implementingright()andbottom()method for integer rectangles, a poor choice that makes hard to write pixel-perfect code and force a lot of+1and-1in code: floating point rectangles are ok, and the mistake on the integer case is acknowledged in the documentation (but unfortunately cannot be removed because of backward compatibility reasons).What is your end goal here?
I thought you were asking for comments, so I commented.
I think the view that
substringin Java has a "quirk" because uses the[a, b[convention for intervals is questionable.That "semi-open interval" is in my opinion the correct approach (may be on par or second only to a
start/sizeapproach). A "boundary included"[a, b]would instead be worse for many reasons.Java has no "quirk" here: it's the correct thing to do (and please note that I'm surely NOT a Java fan, at all).