Indices Point Between Elements
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Indices Point Between Elements
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Re: Indices Point Between Elements
#2The visuals are definitely valuable in explaining this.
It used to be popular, and still is in some circles, to debate whether programming languages ought start array indexing at 0 or 1.
When talking about this with other programmers, I've discovered that a lot of the issues/confusion could be avoided by consistent use of terminology: Offsets/offsetting always being zero-based and indexes/indexing always being one-based.
Using rulers and birthdays also helps to explain differences. You're in the first year before your first birthday, being zero (whole) years old.
To make matters potentially more confusing, culturally, I remember something about the ground floor in the UK buildings not being "Floor 1" like it is in the United States.
Re: Indices Point Between Elements
#3Great teaching tool, thank you.
Re: Indices Point Between Elements
#4This is the mental model I use.
Re: Indices Point Between Elements
#5Further notes about half open intervals and why starting at zero is a good idea: http://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF
Re: Indices Point Between Elements
#6See also https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E... ("Why numbering should start at zero")
Re: Indices Point Between Elements
#7When you talking about where zero-width regexes match, this mental model certainly helps, and I find it consistent otherwise too.
Re: Indices Point Between Elements
#8See also https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E... ("Why numbering should start at zero")
And the HN discussion: https://news.ycombinator.com/item?id=9761355
Re: Indices Point Between Elements
#9People have taken different approaches to this in bioinformatics for numbering intervals of dna bases in chromosomes. I think this approach is catching on, though. In that realm, it's important to speak unambiguously about insertions and deletions, and the "interbase" mental model makes it a lot clearer.
edit: Probably the most popular genome browser, based at UC Santa Cruz, uses this zero-based, half-open numbering internally. But, at some point in the past, biologists developed an expectation that numbering would be 1-based. So the Santa Cruz genome browser actually adds 1 to the start position of everything for display purposes.
Re: Indices Point Between Elements
#10The visuals are definitely valuable in explaining this. It used to be popular, and still is in some circles, to debate whether programming languages ought start array indexing at 0 or 1. When talking about this with other programmers, I've discovered that a lot of the issues/confusion could be avoided by consistent use of terminology: Offsets/offsetting always being zero-based and indexes/indexing always being one-ba…
I remember something about the ground floor in the UK buildings not being "Floor 1" like it is in the United States.
Actually, that's perfectly explained with your offset vs. index terminology. In some countries, the floor number is an index within the array of floors. In others, it's an offset from the ground.