Old 08-25-2017, 05:41 AM   #1
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Default C++17

Just about to start coding the Control Surface Integrator, anyone know of a reason(s) why I should use/not use C++17 compilers for the project ?
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Old 08-25-2017, 06:37 AM   #2
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Reasons why you might not want to use it (or even C++11 compatible compilers) :

1) If you need to support ancient macOS-X versions. macOS-X 10.7 is the first one to have support for C++11. (More precisely, support for the C++11 standard library.) Newer C++ standards might require even later macOS versions.
2) If you need to support Windows XP. I have never got the so called "Windows XP compatibility" working with the newer Visual Studio versions. (Like VS2015 or VS2017.) The resulting binaries simply have not worked on XP for me or for people who have tried to test the binaries. It might work if the end user Windows XP installation is completely up to date with SP3 and all possible updates. I never bothered testing that scenario myself.
3) The Microsoft C++ compiler and standard library and Apple's compiler/library are not at the same level of standard compliance. If you write code that compiles for macOs, it might not work with the Microsoft compiler and vice versa. So you need to be careful which language and standard library features you use. Both platforms have good, but not complete, C++11/14 coverage now, though.
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Old 08-26-2017, 12:10 PM   #3
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As usual, good points, thanks Xen.
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Old 08-26-2017, 04:54 PM   #4
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Do any of you guys use "auto" for your types?

It feels wrong to me somehow
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Old 08-26-2017, 05:05 PM   #5
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Quote:
Originally Posted by Garrick View Post
Do any of you guys use "auto" for your types?

It feels wrong to me somehow
I grew up on a curious mix, assembly, C, and Smalltalk.

So, hell yeah, I'll be using auto wherever I can
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Old 08-26-2017, 05:22 PM   #6
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Quote:
Originally Posted by Geoff Waddington View Post
I grew up on a curious mix, assembly, C, and Smalltalk.

So, hell yeah, I'll be using auto wherever I can
Assembly infers type? Is there no end to this madness.
Well that shows how much I know. I thought assembly would be super dupa strict and make you be explicit about everything.

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Old 08-26-2017, 06:17 PM   #7
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Quote:
Originally Posted by Garrick View Post
Do any of you guys use "auto" for your types?

It feels wrong to me somehow
It's highly debatable if "auto" is that useful for trivial stuff like integer or floating point types, but it's clearly useful when more complicated types are involved. For example, do you want to write

Code:
std::unique_ptr<MyFancyObject<String>> o = std::make_unique<MyFancyObject<String>>("foo");
or would you prefer

Code:
auto o = std::make_unique<MyFancyObject<String>>("foo");
?

And yeah, I do use "auto" regularly.
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Old 08-26-2017, 10:05 PM   #8
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Quote:
Originally Posted by Xenakios View Post
It's highly debatable if "auto" is that useful for trivial stuff like integer or floating point types, but it's clearly useful when more complicated types are involved. For example, do you want to write

Code:
std::unique_ptr<MyFancyObject<String>> o = std::make_unique<MyFancyObject<String>>("foo");
or would you prefer

Code:
auto o = std::make_unique<MyFancyObject<String>>("foo");
?

And yeah, I do use "auto" regularly.
Whoa !!
Yeah I can see now how auto could be a godsend.

Especially in your example where your fancy object's name will pretty much document itself and so easier to reason about.

This is good, it's making me re-think the whole thing.

Like you say, it has limited usefulness with primitives, but if you did, how do you cast from one type to another if you're not explicit what type it originally was?
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Old 08-27-2017, 03:57 AM   #9
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Quote:
Originally Posted by Garrick View Post
Assembly infers type? Is there no end to this madness.
Well that shows how much I know. I thought assembly would be super dupa strict and make you be explicit about everything.
Haha, I more meant Smalltalk, but you got me thinking about this

In a way assembly does have a notion something like type deduction sometimes, here's an example of what I mean.

In our old quirky friend Intel 8088 we can say something like:

Mov AL, SUM // where AL is the lower half (8 bits) of AX therefore 1 byte is moved

Mov AX, SUM // where AX is the whole 16 bit register therefore 2 bytes are moved.

Now, this isn't really typing, you can treat the 8 bits in AL as a character, set of bit flags, or any other data type, and similar for the 16 bits in AX.

So in a way there is some notion of types in at least some assemblers.

Other than that assembler (in vonNeumann architecture processors) is the opposite of strict, it allows you to point to any memory location and treat it as a value, a pointer, code that can be executed, or anything else you can dream up.

Assembly is an extremely powerful and dangerous place, the wild west of anarchy, if you will, no restrictions whatsoever
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Old 08-27-2017, 06:51 AM   #10
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Quote:
Originally Posted by Garrick View Post
how do you cast from one type to another if you're not explicit what type it originally was?
Basically just like one normally would, since casting usually requires just the new destination type to be written out in the code. The compiler obviously knows all the time what the original type is. ("auto" is completely a compile time thing.)

If the cast destination type needs to be determined from an "auto" type variable, that's also possible to do, with "decltype".

So nonsense like this is possible but probably never useful with primitive types :
Code:
auto intnumber = 777;
auto destnumber = 0.5;
auto cast_number = static_cast<decltype(destnumber)>(intnumber);
A much more useful example of "auto" usage, which couldn't even be written without "auto" if one wishes to keep the functions as C++11 lambdas for as long as possible :

Code:
auto make_mapping_functions(float minv, float maxv, float middleval)
{
	auto normtovaluefunc = [minv,maxv,middleval](float, float, float normval)
	{
		if (normval<0.5f)
			return jmap(normval, 0.0f, 0.5f, minv, middleval);
		else return jmap(normval, 0.5f, 1.0f, middleval, maxv);
	};
	auto valuetonormfunc = [minv,maxv,middleval](float, float, float val)
	{
		if (val < middleval)
			return jmap(val, minv, middleval, 0.0f, 0.5f);
		else return jmap(val, middleval, maxv, 0.5f, 1.0f);
	};
	return std::make_pair(normtovaluefunc, valuetonormfunc);
}
// usage :
auto mapfuncs = make_mapping_functions(0.1f, 10.0f, 1.0f);
NormalisableRange<float> prrange(0.1f, 10.0f, mapfuncs.first, mapfuncs.second);
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Old 08-28-2017, 02:41 AM   #11
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Quote:
Originally Posted by Xenakios View Post
Basically just like one normally would, since casting usually requires just the new destination type to be written out in the code. The compiler obviously knows all the time what the original type is. ("auto" is completely a compile time thing.)

If the cast destination type needs to be determined from an "auto" type variable, that's also possible to do, with "decltype".

So nonsense like this is possible but probably never useful with primitive types :
Code:
auto intnumber = 777;
auto destnumber = 0.5;
auto cast_number = static_cast<decltype(destnumber)>(intnumber);
A much more useful example of "auto" usage, which couldn't even be written without "auto" if one wishes to keep the functions as C++11 lambdas for as long as possible :

Code:
auto make_mapping_functions(float minv, float maxv, float middleval)
{
	auto normtovaluefunc = [minv,maxv,middleval](float, float, float normval)
	{
		if (normval<0.5f)
			return jmap(normval, 0.0f, 0.5f, minv, middleval);
		else return jmap(normval, 0.5f, 1.0f, middleval, maxv);
	};
	auto valuetonormfunc = [minv,maxv,middleval](float, float, float val)
	{
		if (val < middleval)
			return jmap(val, minv, middleval, 0.0f, 0.5f);
		else return jmap(val, middleval, maxv, 0.5f, 1.0f);
	};
	return std::make_pair(normtovaluefunc, valuetonormfunc);
}
// usage :
auto mapfuncs = make_mapping_functions(0.1f, 10.0f, 1.0f);
NormalisableRange<float> prrange(0.1f, 10.0f, mapfuncs.first, mapfuncs.second);
Nice !!

I've got Scott Meyers Effective Modern C++ and, of course, a ton of web resources.

Any particular resources you think would help an old C veteran with the strange additions of assembly and Smalltalk get up to speed on modern C++ ?

Closures/lambdas are called blocks in Smalltalk and they are highly powerful and super handy as in C++, so I get the lambdas thing.

Everyone is pushing the reasons to use constexpr and that's cool.

Just getting into Jason Turner's C++ Weekly vids.

So, veteran OO programmer, newly converting to modern C++.

Thanks for any help.
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Old 08-28-2017, 07:37 AM   #12
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Quote:
Originally Posted by Geoff Waddington View Post
Any particular resources you think would help an old C veteran with the strange additions of assembly and Smalltalk get up to speed on modern C++ ?

Everyone is pushing the reasons to use constexpr and that's cool.
https://isocpp.org/ sometimes has interesting links.

constexpr stuff is cool if it happens to work, but I personally haven't spent much effort in making things compatible with that. So much stuff just has to happen at runtime, after all...
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Old 09-05-2017, 11:12 PM   #13
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Also check out CPPcon and BoostCon on Youtube. They publish videos of their conference lectures, many of which are focused around modern, idiomatic C++. I usually change the playspeed to 1.5x or 2x unless someone's a particularly quick speaker. That way it doesn't take so much time to sit through a talk. You could spend months watching videos and not run out of content.

The CPP subreddit tends to have pretty decent content as well.

It's probably really difficult to come up to speed since most modern tutorials will assume knowledge of older C++, but some of that older C++ is obsolete or bad practice. If you're looking for a book that teaches modern C++ (C++14) while also covering a lot of fundamentals, this one might be good.


Quote:
Originally Posted by Xenakios View Post
So much stuff just has to happen at runtime, after all...
The best part about constexpr functions is they can be used at compile time or run time, depending on the context in which they're evaluated. With the more relaxed rules of C++17, a lot of times you can slap a constexpr on an existing runtime function and have it work at compile time for free.
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Old 09-08-2017, 10:00 AM   #14
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Just one example about what I like about just C++11, it's possible to quite trivially make functions that are essentially just for loops with a descriptive name :
Code:
    template<typename F>
    void for_each_selected_zone(F&& func, bool usemutex=false)
    {
		for (auto& e : m_selected_zones)
		{
			if (usemutex)
				processor.m_mutex.lock();
			func(processor.getSamplerSound(e));
			if (usemutex)
				processor.m_mutex.unlock();
		}
    }

// usage :

for_each_selected_zone([this](XenSamplerSound* snd)
{
  snd->m_num_outchans = m_numoutchanscombo.getSelectedId() - 1;
},true);
IMHO this can really reduce the chances of making a mistake while writing the iteration code.
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Old 09-11-2017, 03:04 AM   #15
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Having some fun, having some frustration fighting with compiler on types, whilst learning good hygienic modern C++

Find myself typing 'const' an lot, maybe they should have made it the default and used the keyword 'unconst' instead

Talk about a breaking change !!
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