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> auto v = {1,2,3,5,8,13}; > Kaboom. Oops. You can use auto, or you can use {} to make a vector, but you can't do both at the same time! IMO it would be more

> auto v = {1,2,3,5,8,13}; > Kaboom. Oops. You can use auto, or you can use {} to make a vector, but you can't do both at the same time! IMO it would be more confusing if that created a vector<int>. Unless the compiler is reading your mind, how is it supposed to know you meant a vector<int>, a set<int>, deque<int>, a struct { int a,b,c,d,e,f}, or some other object who's constructor can take 6 ints?

mikeash 12y ago
The way most other languages handle it is that the list literal construct just creates a list, and if you want something else then you need to explicitly convert. For example, in Python: x = [1, 2, 3, 5, 8, 13] # this is a list of integers y = set([1, 2, 3, 5, 8, 13]) # this is a set of integers There's nothing inherently wrong with C++'s initializer list approach. Nor is there anything inherently wrong with auto. But they collide in unfortunate ways because they haven't been designed such that they go well together. C++ is full of things like this. Responding with "well, that makes the most sense" for any given feature is missing the point entirely.
- jlarocco 12y ago
  > The way most other languages handle it is that the list literal construct just creates a list, and if you want something else then you need to explicitly convert. > For example, in Python: > x = [1, 2, 3, 5, 8, 13] # this is a list of integers > y = set([1, 2, 3, 5, 8, 13]) # this is a set of integers Actually, that's not the best way to do it: y = {1, 2, 3, 5, 8, 13} # this is a set of integers without creating a list first. z = set(1, 2, 3, 5, 8, 13) # so is this In C++ {} is syntactic sugar for "Create an initializer_list with these values," which is what happens when it's assigned to an "auto" variable. Not surprising at all. If you want a different type, you need to specify the type that you want. Maybe it's confusing to beginners and people who don't take the time to learn the language, but C++ isn't catering to those people. Don't get me wrong, there are a lot of "gotchas" in C++, I just don't think the two you've posted are very bad.
  - mikeash 12y ago
    Um, the whole point of this discussion is about the claim that C++ is a good language for beginners to learn. I have problems with using C++ to build real projects with experienced programmers too, but those are mostly different problems.
- maxlybbert 12y ago
  Well, to be fair, with "auto x = { 1, 2, 3, 4, 5, 6}" you will get a variable named "x", but it won't be a std::vector<int> (it'll be a std::initializerList<int>).
jerf 12y ago
Go would do: v := []TYPEHERE{1, 2, 3} where TYPEHERE is the type of array[1] that you're creating. Is there any equivalent C++ technique here? Explaining all the machinery may blow out a novice's mind, but I think explaining "You need to give C++ some clue about the type" isn't so bad. [1]: Before you complain I just created a slice, remember the slice has to point at an array; I've created both a slice and an array so it's not "wrong" to say I've created an array with that syntax.
- TheCoelacanth 12y ago
  Yes, C++ has no shortage of ways to initialize variables. Any of these should work TYPENAME v {1, 2, 3}; TYPENAME v = {1, 2, 3}; auto v = TYPENAME {1, 2, 3};

mikeash 12y ago

The way most other languages handle it is that the list literal construct just creates a list, and if you want something else then you need to explicitly convert. For example, in Python: x = [1, 2, 3, 5, 8, 13] # this is a list of integers y = set([1, 2, 3, 5, 8, 13]) # this is a set of integers There's nothing inherently wrong with C++'s initializer list approach. Nor is there anything inherently wrong with auto. But they collide in unfortunate ways because they haven't been designed such that they go well together. C++ is full of things like this. Responding with "well, that makes the most sense" for any given feature is missing the point entirely.

jlarocco 12y ago
> The way most other languages handle it is that the list literal construct just creates a list, and if you want something else then you need to explicitly convert. > For example, in Python: > x = [1, 2, 3, 5, 8, 13] # this is a list of integers > y = set([1, 2, 3, 5, 8, 13]) # this is a set of integers Actually, that's not the best way to do it: y = {1, 2, 3, 5, 8, 13} # this is a set of integers without creating a list first. z = set(1, 2, 3, 5, 8, 13) # so is this In C++ {} is syntactic sugar for "Create an initializer_list with these values," which is what happens when it's assigned to an "auto" variable. Not surprising at all. If you want a different type, you need to specify the type that you want. Maybe it's confusing to beginners and people who don't take the time to learn the language, but C++ isn't catering to those people. Don't get me wrong, there are a lot of "gotchas" in C++, I just don't think the two you've posted are very bad.
- mikeash 12y ago
  Um, the whole point of this discussion is about the claim that C++ is a good language for beginners to learn. I have problems with using C++ to build real projects with experienced programmers too, but those are mostly different problems.
maxlybbert 12y ago
Well, to be fair, with "auto x = { 1, 2, 3, 4, 5, 6}" you will get a variable named "x", but it won't be a std::vector<int> (it'll be a std::initializerList<int>).

jerf 12y ago

Go would do: v := []TYPEHERE{1, 2, 3} where TYPEHERE is the type of array[1] that you're creating. Is there any equivalent C++ technique here? Explaining all the machinery may blow out a novice's mind, but I think explaining "You need to give C++ some clue about the type" isn't so bad. [1]: Before you complain I just created a slice, remember the slice has to point at an array; I've created both a slice and an array so it's not "wrong" to say I've created an array with that syntax.

TheCoelacanth 12y ago
Yes, C++ has no shortage of ways to initialize variables. Any of these should work TYPENAME v {1, 2, 3}; TYPENAME v = {1, 2, 3}; auto v = TYPENAME {1, 2, 3};