digitalmars.D.learn - Help me write "saveAll"
- monarch_dodra (49/49) Dec 21 2012 There are a lot of algorithms in std.algorithm that operate on
- H. S. Teoh (7/19) Dec 21 2012 What about using a mixin? I know it's ugly, but at least you don't have
- monarch_dodra (3/23) Dec 21 2012 Hum. That's a solution I guess. I'm tying to see if I can't get
- Joshua Niehus (17/28) Dec 21 2012 Sorry if im misunderstanding, but doesn't filter do this?
- monarch_dodra (15/46) Dec 21 2012 I think there may be some misunderstanding. It's more like this;
- Timon Gehr (4/24) Dec 21 2012 Use a phobos tuple?
- monarch_dodra (31/62) Dec 22 2012 Victory! It works that way!
There are a lot of algorithms in std.algorithm that operate on
"foo(Range, Needles...)(Range range, Needles needles)".
Needles can be anything, in particular, either an "element" or a
"range".
The thing is that every now and then, you want to save the
entirety of (the ranges) inside needles. EG, I want to be able to
write:
foo(range, needles.saveAll);
I'm having trouble. I did two iterations:
//----
auto saveAll(Ranges...)(Ranges ranges) property
{
auto ret = ranges;
foreach (Index, Type; Ranges)
static if (isForwardRange!Type)
ret[Index] = ranges[Index];
return ret;
}
//----
This doesn't work, because: Error: functions cannot return a tuple
So that's that.
The next try was:
//----
void saveAll(Ranges...)(in Ranges iRanges, ref Ranges oRanges)
property
{
TypeTuple!Ranges ret = ranges;
foreach (Index, Type; Ranges)
static if (isForwardRange!Type)
ret[Index] = ranges[Index];
return ret;
}
//----
This doesn't either, because a function can't have double varargs
arguments. It's ambiguous...
So this left me with the option of just inlining into the code:
//----
Needles savedNeedles = needles;
foreach (Index, Type; Needles)
static if (isForwardRange!Type)
savedNeedles[Index] = needles[Index];
size_t r = startsWith!pred(haystack, savedNeedles);
//----
It works, but is kind of ugly, I'd have really wanted to be able
to just write:
//----
size_t r = startsWith!pred(haystack, needles.saveAll);
//----
Any thought on how do get this working?
Dec 21 2012
On Fri, Dec 21, 2012 at 06:01:13PM +0100, monarch_dodra wrote:There are a lot of algorithms in std.algorithm that operate on "foo(Range, Needles...)(Range range, Needles needles)". Needles can be anything, in particular, either an "element" or a "range". The thing is that every now and then, you want to save the entirety of (the ranges) inside needles. EG, I want to be able to write: foo(range, needles.saveAll); I'm having trouble. I did two iterations:[...]Any thought on how do get this working?What about using a mixin? I know it's ugly, but at least you don't have to copy-n-paste lots of boilerplate every time. T -- LINUX = Lousy Interface for Nefarious Unix Xenophobes.
Dec 21 2012
"monarch_dodra" <monarchdodra gmail.com> On Friday, 21 December 2012 at 17:27:32 UTC, H. S. Teoh wrote:On Fri, Dec 21, 2012 at 06:01:13PM +0100, monarch_dodra wrote:Hum. That's a solution I guess. I'm tying to see if I can't get something to work with Tuple and ParameterTypeTuple...There are a lot of algorithms in std.algorithm that operate on "foo(Range, Needles...)(Range range, Needles needles)". Needles can be anything, in particular, either an "element" or a "range". The thing is that every now and then, you want to save the entirety of (the ranges) inside needles. EG, I want to be able to write: foo(range, needles.saveAll); I'm having trouble. I did two iterations:[...]Any thought on how do get this working?What about using a mixin? I know it's ugly, but at least you don't have to copy-n-paste lots of boilerplate every time. T
Dec 21 2012
On Friday, 21 December 2012 at 17:01:14 UTC, monarch_dodra wrote:There are a lot of algorithms in std.algorithm that operate on "foo(Range, Needles...)(Range range, Needles needles)". Needles can be anything, in particular, either an "element" or a "range". The thing is that every now and then, you want to save the entirety of (the ranges) inside needles. EG, I want to be able to write: foo(range, needles.saveAll); [...snip...] Any thought on how do get this working? size_t r = startsWith!pred(haystack, needles.saveAll);Sorry if im misunderstanding, but doesn't filter do this? Example: import std.stdio, std.algorithm, std.range; void main() { auto x = [ [1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12] ]; //haystack // needle // needle auto y = x.filter!(a => (a == [4, 5, 6] || a == [7, 8, 9])).array; y.writeln; }
Dec 21 2012
On Friday, 21 December 2012 at 20:38:34 UTC, Joshua Niehus wrote:On Friday, 21 December 2012 at 17:01:14 UTC, monarch_dodra wrote:I think there may be some misunderstanding. It's more like this; //---- [1, 2, 3, 4].find(4, 7, [1, 3], [2, 3]); //---- Here, as you can see, the 4 needles are: 4: Element 7: Element [1, 3]: Range [2, 3]: Range In your example, you are just comparing elements: The elements themselves happen to be ranges, but that is irrelevant in the iteration scheme, they remain *elements* in the search. In my example, Filter can't operate the Needle "[1, 3]", because it contains multiple elements.There are a lot of algorithms in std.algorithm that operate on "foo(Range, Needles...)(Range range, Needles needles)". Needles can be anything, in particular, either an "element" or a "range". The thing is that every now and then, you want to save the entirety of (the ranges) inside needles. EG, I want to be able to write: foo(range, needles.saveAll); [...snip...] Any thought on how do get this working? size_t r = startsWith!pred(haystack, needles.saveAll);Sorry if im misunderstanding, but doesn't filter do this? Example: import std.stdio, std.algorithm, std.range; void main() { auto x = [ [1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12] ]; //haystack // needle // needle auto y = x.filter!(a => (a == [4, 5, 6] || a == [7, 8, 9])).array; y.writeln; }
Dec 21 2012
On 12/21/2012 06:01 PM, monarch_dodra wrote:
There are a lot of algorithms in std.algorithm that operate on
"foo(Range, Needles...)(Range range, Needles needles)".
Needles can be anything, in particular, either an "element" or a "range".
The thing is that every now and then, you want to save the entirety of
(the ranges) inside needles. EG, I want to be able to write:
foo(range, needles.saveAll);
I'm having trouble. I did two iterations:
//----
auto saveAll(Ranges...)(Ranges ranges) property
{
auto ret = ranges;
foreach (Index, Type; Ranges)
static if (isForwardRange!Type)
ret[Index] = ranges[Index];
return ret;
}
//----
This doesn't work, because: Error: functions cannot return a tuple
So that's that.
...
Use a phobos tuple?
return tuple(ret)
The caller can use .expand.
Dec 21 2012
On Saturday, 22 December 2012 at 02:58:16 UTC, Timon Gehr wrote:On 12/21/2012 06:01 PM, monarch_dodra wrote:Victory! It works that way! //---- auto saveAll(Stuff...)(Stuff stuff) { Stuff ret = stuff; foreach(ref v; ret) ++v; return tuple(ret); } void foo(Stuff...)(Stuff stuff) { bar(stuff.saveAll().expand); } void bar(Stuff...)(Stuff stuff) { foreach (v; stuff) v.writeln(); } void main() { foo(1, 2, 3); } //---- The only limitation is that I can't declare it as a property. I get: main.d(11): Error: properties can only have zero, one, or two parameter I'd say that a bug (or at least, an unnecessary restriction), but I can live with it. Thankyou!There are a lot of algorithms in std.algorithm that operate on "foo(Range, Needles...)(Range range, Needles needles)". Needles can be anything, in particular, either an "element" or a "range". The thing is that every now and then, you want to save the entirety of (the ranges) inside needles. EG, I want to be able to write: foo(range, needles.saveAll); I'm having trouble. I did two iterations: //---- auto saveAll(Ranges...)(Ranges ranges) property { auto ret = ranges; foreach (Index, Type; Ranges) static if (isForwardRange!Type) ret[Index] = ranges[Index]; return ret; } //---- This doesn't work, because: Error: functions cannot return a tuple So that's that. ...Use a phobos tuple? return tuple(ret) The caller can use .expand.
Dec 22 2012