Why ByChunk is not regnize by st.range.takeOne and why Section has no value
Dear, Some problem to build this code: http://fpaste.org/147327/75948141/ $ ldc2 fasta_test.d /usr/include/d/std/range.d(3605): Error: template std.array.save cannot deduce function from argument types !()(ByChunk), candidates are: /usr/include/d/std/array.d(554):std.array.save(T)(T[] a) fasta_test.d(46): Error: template instance std.range.takeOne!(ByChunk) error instantiating fasta_test.d(88):instantiated from here: Parser!(Fasta, ByChunk) fasta_test.d(79): Error: type Section!((words) => words[0] == '>', (words) => words[0] == '\x0a') has no value fasta_test.d(50): Error: template std.algorithm.countUntil cannot deduce function from argument types !(__lambda3)(ubyte[]), candidates are: /usr/include/d/std/algorithm.d(5406): std.algorithm.countUntil(alias pred = "a == b", R, Rs...)(R haystack, Rs needles) if (isForwardRange!R && Rs.length > 0 && isForwardRange!(Rs[0]) == isInputRange!(Rs[0]) && is(typeof(startsWith!pred(haystack, needles[0]))) && (Rs.length == 1 || is(typeof(countUntil!pred(haystack, needles[1..__dollar]) Thanks for your help
Re: Why ByChunk is not regnize by st.range.takeOne and why Section has no value
On 11/02/2014 04:58 PM, bioinfornatics wrote:
> Dear,
> Some problem to build this code: http://fpaste.org/147327/75948141/
>
>
> $ ldc2 fasta_test.d
> /usr/include/d/std/range.d(3605): Error: template std.array.save
> cannot deduce function from argument types !()(ByChunk),
> candidates are:
I think that is due to the too permissive template constraint of takeOne
in phobos/std/range.d. Even though it say "isInputRange!R", it clearly
needs "isForwardRange!R" because it calls .save() on that range:
@property auto save() { return Result(_source.save, empty); }
So, the following is wrong:
auto takeOne(R)(R source) if (isInputRange!R)
It should be:
auto takeOne(R)(R source) if (isForwardRange!R)
If you modify range.d locally to require ForwardRange, you will see that
your following call will get an error message because byChunk is not a
ForwardRange:
// Take a piece of byte from current file
ubyte[] buffer = takeOne(inputRange);
I think this issue is already reported as a part of the following bug:
https://issues.dlang.org/show_bug.cgi?id=9724
Ali
Re: Why ByChunk is not regnize by st.range.takeOne and why Section has no value
On Monday, 3 November 2014 at 06:43:50 UTC, Ali Çehreli wrote:
On 11/02/2014 04:58 PM, bioinfornatics wrote:
> Dear,
> Some problem to build this code:
http://fpaste.org/147327/75948141/
>
>
> $ ldc2 fasta_test.d
> /usr/include/d/std/range.d(3605): Error: template
std.array.save
> cannot deduce function from argument types !()(ByChunk),
> candidates are:
I think that is due to the too permissive template constraint
of takeOne in phobos/std/range.d. Even though it say
"isInputRange!R", it clearly needs "isForwardRange!R" because
it calls .save() on that range:
@property auto save() { return Result(_source.save, empty);
}
So, the following is wrong:
auto takeOne(R)(R source) if (isInputRange!R)
It should be:
auto takeOne(R)(R source) if (isForwardRange!R)
If you modify range.d locally to require ForwardRange, you will
see that your following call will get an error message because
byChunk is not a ForwardRange:
// Take a piece of byte from current file
ubyte[] buffer = takeOne(inputRange);
I think this issue is already reported as a part of the
following bug:
https://issues.dlang.org/show_bug.cgi?id=9724
Ali
Ok but I do not see why to use save method for a takeOne function
is possible to write this function without to use it
Re: Why ByChunk is not regnize by st.range.takeOne and why Section has no value
On Monday, November 03, 2014 21:03:51 bioinfornatics via Digitalmars-d-learn wrote: > Ok but I do not see why to use save method for a takeOne function > is possible to write this function without to use it It looks like the idea was that beacause you know that there's only one element, you can make it random-access range with opSlice and popBack and the whole shebang. And that works great if the range is at least a forward range, but it currently falls apart with an input range, because while you can easily emulate stuff like back and opIndex by forwarding it to front, save can't be emulated so easily. So, either front needs to be accessed and saved in the Result struct rather than than simply having it contain the range that it's forwarding to, or it needs to have another branch of the static if for handling input ranges separately. Though to be honest, I'm not sure that using takeOne makes a lot of sense over take in that case. You don't really get a performance boost, and since you can't add on the random-access range capabilities without making it eager and saving the result of front (which is an iffy thing to do with some input ranges), it's really not adding anything over plain take. I'd honestly favor just fixing takeOne's template constraint so that it checked for forward ranges. The only reason that I see to make takeOne work with input ranges is simply so that no one will be surprised when it doesn't work with an input range. But that's not really adding any useful functionality as far as I can tell. Though maybe there's something that I'm missing. - Jonathan M Davis
Re: Why ByChunk is not regnize by st.range.takeOne and why Section has no value
On Monday, 3 November 2014 at 21:03:51 UTC, bioinfornatics wrote:
On Monday, 3 November 2014 at 06:43:50 UTC, Ali Çehreli wrote:
On 11/02/2014 04:58 PM, bioinfornatics wrote:
> Dear,
> Some problem to build this code:
http://fpaste.org/147327/75948141/
>
>
> $ ldc2 fasta_test.d
> /usr/include/d/std/range.d(3605): Error: template
std.array.save
> cannot deduce function from argument types !()(ByChunk),
> candidates are:
I think that is due to the too permissive template constraint
of takeOne in phobos/std/range.d. Even though it say
"isInputRange!R", it clearly needs "isForwardRange!R" because
it calls .save() on that range:
@property auto save() { return Result(_source.save, empty);
}
So, the following is wrong:
auto takeOne(R)(R source) if (isInputRange!R)
It should be:
auto takeOne(R)(R source) if (isForwardRange!R)
If you modify range.d locally to require ForwardRange, you
will see that your following call will get an error message
because byChunk is not a ForwardRange:
// Take a piece of byte from current file
ubyte[] buffer = takeOne(inputRange);
I think this issue is already reported as a part of the
following bug:
https://issues.dlang.org/show_bug.cgi?id=9724
Ali
Ok but I do not see why to use save method for a takeOne
function
is possible to write this function without to use it
Example:
auto takeOne(R)(ref R source) if (isInputRange!R)
{
static if (hasSlicing!R)
{
return source[0 .. !source.empty];
}
else
{
typeof(R.front) r;
if(!source.empty){
r = source.front;
source.popFront();
}
return r;
}
}
