static array is no range?
```
import std.algorithm;
char[1024] buffer;
buffer.find("LOCATION: "); // get error about how all the
different versions of find don't match
```
```
import std.algorithm;
char[1024] buffer;
buffer[0..$].find("LOCATION: "); // works as expected
```
Before trying the slice I manually pragma(msg) all the template
constraints to see why it was failing. Apparently a static array
is not a ForwardRange. Now, there is probably a good reason for
that, that is not what I want to discuss.
The point is that it is rather hard to find out what went wrong.
What I would like the compiler to emit is this: `Error: buffer is
not a ForwardRange`. But I know that wouldn't be so easy.
At least the compiler shouldn't show me candidates with
non-matching arguments length (e.g.
`std.algorithm.searching.find(alias pred, InputRange)(InputRange
haystack) if (isInputRange!InputRange)`)
Re: static array is no range?
On Saturday, 5 September 2015 at 11:12:17 UTC, Sebastiaan Koppe
wrote:
```
import std.algorithm;
char[1024] buffer;
buffer.find("LOCATION: "); // get error about how all the
different versions of find don't match
```
```
import std.algorithm;
char[1024] buffer;
buffer[0..$].find("LOCATION: "); // works as expected
```
You can do instead:
buffer[].find("LOCATION: ");
Before trying the slice I manually pragma(msg) all the template
constraints to see why it was failing. Apparently a static
array is not a ForwardRange. Now, there is probably a good
reason for that, that is not what I want to discuss.
The point is that it is rather hard to find out what went wrong.
What I would like the compiler to emit is this: `Error: buffer
is not a ForwardRange`. But I know that wouldn't be so easy.
At least the compiler shouldn't show me candidates with
non-matching arguments length (e.g.
`std.algorithm.searching.find(alias pred,
InputRange)(InputRange haystack) if (isInputRange!InputRange)`)
Yes, static arrays aren't ranges. The main reason is that static
arrays are value type (ie: you copy them arround when passing
them to functions which usually has a huge cost) where ranges are
reference type (no copy, lighter, not always better as it makes
optimisation more complicated).
The standard library is designed arround ranges to make sure that
you are not copying 1024-bytes long structures arround by
accident: you'd have to do that explicitely. As a consequence,
you must generally slice arrays when passing them to phobos
functions (not always true but a good rule of thumb).
That said, if you want to benefit from array-specific
optimisations such as loop-unrolling you are generally better of
using a good old foreach and implementing the logic yourself.
Yes, it is sad, I agree.
Re: static array is no range?
On Sunday, 6 September 2015 at 00:25:10 UTC, cym13 wrote:
Yes, static arrays aren't ranges. The main reason is that
static arrays are value type (ie: you copy them arround when
passing them to functions which usually has a huge cost) where
ranges are reference type (no copy, lighter, not always better
as it makes optimisation more complicated).
The standard library is designed arround ranges to make sure
that you are not copying 1024-bytes long structures arround by
accident: you'd have to do that explicitely. As a consequence,
you must generally slice arrays when passing them to phobos
functions (not always true but a good rule of thumb).
That actually makes a lot of sense.
That said, if you want to benefit from array-specific
optimisations such as loop-unrolling you are generally better
of using a good old foreach and implementing the logic
yourself. Yes, it is sad, I agree.
While I like speed, 95% of my applications can be 4x as slow, and
no-one would give a damn. Plus, I have only limited time so I try
to be efficient by writing as little code as possible (while
still getting work done.)
What I was trying to say is that endorsed idiomatic D code (UFCS
combined with function overloading+constraints), produces
terrible error messages. Which means every newcomer sees that
awful stuff and decides to implement said algorithm himself. That
is not productivity.
This is arguably the poorest and most neglected aspect of D.
Without messing up internals the best I can think of is this:
```
auto forwardRange(alias R)()
{
import std.traits;
import std.range;
static if(!isForwardRange!(typeof(R))) static
assert(0,"Nonono... "~__traits(identifier,R)~" not a
ForwardRange");
return R;
}
unittest
{
char[1024] buffer;
import std.algorithm;
forwardRange!buffer.find("LOCATION: ");
}
```
Which is ugly as hell, and probably even worse than the current
state.
