211–220 of 702 posts
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That's just convention though. There's no reason "[x]" couldn't have been defined to be "+ (x - 1) * sizeof". There would be no runtime cost to this, and the compile time penalty would be tiny even on ancient systems.
Is `(x - 1)` not a runtime cost if `x` is a runtime variable?
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An assembler spillover into C.
Was C ever much more than a veneer on top of assembler? Don't get me wrong, it's why I like C.
Maybe in the very early days, but that necessarily had to end as soon as compilers started doing non-trivial optimizations. Today, C is very far from being "portable assembly".
It really comes down to a choice between a machine-focused (0) or human-focused (1) approach. The 0 makes a lot of sense in a C pointer world where memcpy and other alike functions can be written very thight. The 1 makes a lot of sense in a human world, when we count, we start at 1, we talk about the "1st", counting on finger starts with 1, etc. I once were at a Lua (1 indexed language) conference where this was disc…
If I ask you to count the number of red balls in a bag with only 3 yellow balls, then the initial count in your head is 0, you inspect the balls one by one, never encountering a red ball, and thus never incrementing the count. And then you pronounce your final count of 0. So that's counting starting from 0.
What you call "starting at 1" is not so much the start as it is the first increment, which need not arise.
Arrays in Ada start at the index based on the index type of the array. You can even use an enumeration type as the index: type Day is (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday); type Hours is array (Day range ) of Natural; V : Hours (Monday .. Friday); Which index type you should use depends on the problem that you're trying to model. You can find out the lower/higher end of a type/variable with…
If you don't understand this, you should not be writing computer software.
In English, the day of your birth, when you're 0, is also your birthday. So, technically speaking, when you're turning 29, you're having your 30th birthday, even though no-one says it like that. I always assumed 0-based indexing was something like that, similar to the example given about the ground floor being the 0th floor in some countries and the first floor in others. Another example is if I'm getting directions…
That depends on whether you think of "birthday" as synonymous with "the actual day of my birth" or "a celebration of the day of my birth". I think most of us actual consider it the latter, which is why the first one is after you've been born for a year. If you look up the definition of "birthday" (one word, no spaces) you'll see that there is often some acknowledgement of this in the differing definitions offered.
> "Walk 3 blocks that way", in my mind I conceptualize that I'm presently on the 0th block and I don't yet count it.
You have to decide whether the person is saying something is on the third block from your position, or you need to walk about three blocks of distance. You probably do this automatically based on how close you are to the edge of the current block. If I'm 30 feet from the edge of a black, I'm probably not going to include the current block in that distance. I imagine you probably won't as well.
> they're all fairly intuitive. I never realized that 0-based indexing required such a deep background to be justified.
I think they're only intuitive because we're all context sensitive. The issue is when people don't have the same context, or the context no longer strictly makes sense when the terminology is used in contexts that make less sense.
As an offset, and in programming languages where it's easy to see it's an offset (C), it makes perfect sense. In languages where that's all hidden from you, and you're really just referencing the nth item in a list, the 0th item doesn't make a lot of sense. People in these different contexts will likely have different ideas of what "intuitive" means with regards to this.
I have always assumed that is just one less operation required to resolve the absolute memory address.
This is primarily the actual answer. While most languages force you to see the array as an array, in C/C++ (in C++ I'm only referring to the memory allocated variable type, not an "array class") you can see it as a pointer and do your own math to address any part of it that you want. And the calculation for that memory address is idx * sizeof(the thing in your array). So the real answer here is that array semantics n…
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> when we count, we start at 1, we talk about the "1st" Although often with an implicit zero. Under typical North American culture, your 1st birthday, for example, is more accurately the first anniversary of your birthday. Your birth is zero indexed.
Oddly(?) though, most parents of young children don't refer to a baby as being "zero years old." Rather, we break them down into smaller units: two days old, six weeks old, four months old.
On the other hand a computer/car/house can also be 10 years old but not 0.
If you ask people which floor of building they're on, it's going to depend on which country they're in. In North America, at least, the first floor you walk into (in a sane city: I understand there are some which do not qualify in this respect due to hills or historic disaster recovery) is the first floor. On other continents, you enter the ground floor and need to take stairs or an elevating device to get to the fir…
But then again people measure distance in feet and write dates as month day year :)
Easy: I have an array with 256 elements. And I want to store the indexes of various elements of the array off in another data structure. So many of them, in fact, that it’s important that the index values each fit into a byte. So, I want the index values to be 0..255, and not 1..256, since 256 doesn’t fit into a byte.
In a minecraft clone I made, each chunk consists of 16 subchunks so that I only need 12 bits to represent the block position in the shader. Technically, the block position ranges from INT32_MIN -> INT32_MAX, but since each subchunk only consists of 16x16x16 blocks I can get away with storing the position in 12 bits and then passing in the subchunk's world position once as a uniform.