I am using elixir-mongo and trying to stream the results of a query. Here's the code...
def archive_stream(z) do
Stream.resource(
fn ->
{jobs, datetime} = z
lt = datetime_to_bson_utc datetime
c = jobs |> Mongo.Collection.find( %{updated_at: %{"$lt": lt}}) |> Mongo.Find.exec
{:cont, c.response.buffer, c}
end,
fn(z) ->
{j, {cont, therest, c}} = next(z)
case cont do
:cont -> {j, {cont, therest, c}}
:halt -> {:halt, {cont, therest, c}}
end
end,
fn(:halt, resp) -> resp end
)
end
All of the sub-bits seem to work (like the query), but when I try to get at the stream, I fail...
Mdb.archive_stream({jobs, {{2013,11,1},{0,0,0}}})|>Enum.take(2)
I get...
(BadArityError) #Function<2.49475906/2 in Mdb.archive_stream/1> with arity 2 called with 1 argument ({:cont, <<90, 44, 0, 0, 7, 95, 105, 100, 0, 82, 110, 129, 221, 102, 160, 249, 201, 109, 0, 137, 233, 4, 95, 115, 108, 117, 103, 115, 0, 51, 0, 0, 0, 2, 48, 0, 39, 0, 0, 0, 109, 97, 110, 97, 103, 101, 114, 45, ...>>, %Mongo.Cursor{batchSize: 0, collection: %Mongo.Collection{db: %Mongo.Db{auth: {"admin", "edd5404c4f906060b125688e26ffb281"}, mongo: %Mongo.Server{host: 'db-stage.member0.mongolayer.com', id_prefix: 57602, mode: :passive, opts: %{}, port: 27017, socket: #Port<0.27099>, timeout: 6000}, name: "db-stage", opts: %{mode: :passive, timeout: 6000}}, name: "jobs", opts: %{}}, exhausted: false, response: %Mongo.Response{buffer: <<188, 14, 0, 0, 7, 95, 105, 100, 0, 82, 110, 129, 221, 102, 160, 249, 201, 109, 0, 137, 242, 4, 95, 115, 108, 117, 103, 115, 0, 45, 0, 0, 0, 2, 48, 0, 33, 0, 0, 0, 114, 101, 116, 97, ...>>, cursorID: 3958284337526732701, decoder: &Mongo.Response.bson_decode/1, nbdoc: 101, requestID: 67280413, startingFrom: 0}}})
(elixir) lib/stream.ex:1020: Stream.do_resource/5
(elixir) lib/enum.ex:1731: Enum.take/2
I'm stumped. Any ideas?
thanks for the help
Dang! Rookie Error.
:halt -> {:halt, {cont, therest, c}} should be _ -> {:halt, z} and fn(:halt, resp) -> resp end should be fn(resp) -> resp end
I've been d**king around with everything but the after function for a day and a half.
A little more explanation for fellow rookies...
the last option in the next_fun() should probably _ inorder to catch other "bad behavior" and not just {:halt}
the after_fn() is only expecting 1 arg and in the above code that would be the z tuple in the last option of the next_fun(). It is not expecting to see :halt and z, just z.
Would like to have REAL experts input.
Related
I want to get a image from my REST API service however haven't found any documentation on how to decode the response body that would be a byte array to an image in Flutter? Anyone with some useful resources, please help...
Use this for your image widget: Image.memory(bytes). You can find more documentation on the Flutter dev website.
Since top rated answer use flutter/widget.dart, this use dart:ui only
Future<Image> tinypng() async {
final bytes = Uint8List.fromList([
137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0,
1, 0, 0, 0, 1, 8, 6, 0, 0, 0, 31, 21, 196, 137, 0, 0, 0, 10, 73, 68, 65,
84, 120, 156, 99, 0, 1, 0, 0, 5, 0, 1, 13, 10, 45, 180, 0, 0, 0, 0, 73,
69, 78, 68, 174, 66, 96, 130 // prevent dartfmt
]);
// copy from decodeImageFromList of package:flutter/painting.dart
final codec = await instantiateImageCodec(bytes);
final frameInfo = await codec.getNextFrame();
return frameInfo.image;
}
This will return a Widget
Image.memory(Uint8List);
I am new to Scala, here i am trying to find the even numbers from 1 to 100, so while i am filtering,i am getting
scala.collection.immutable.Range.Inclusive
scala> var a = List(1 to 100)
a: List[scala.collection.immutable.Range.Inclusive] = List(Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100))
scala> a.filter(x => (x % 2 == 0))
<console>:26: error: value % is not a member of scala.collection.immutable.Range.Inclusive
a.filter(x => (x % 2 == 0))
^
scala> val b = a.filter(x => x % 2 == 0)
<console>:25: error: value % is not a member of scala.collection.immutable.Range.Inclusive
val b = a.filter(x => x % 2 == 0)
^
You're creating a list of Range, not a list with the ints in that range. For that, change it to:
val a = (1 to 10).toList
But #Tim's right, you can filter directly on the Range
You don't need to wrap the Range in a List, just do this:
val a = 1 to 100
a.filter(x => x % 2 == 0)
I need to encode a string to UTF-16LE (and convert to sha1 later), but I'm having some problems. This is what I had tried:
let utf16array = Array("password".utf16)
print(utf16array)
// [112, 97, 115, 115, 119, 111, 114, 100]
But this is what I was expecting:
// [112, 0, 97, 0, 115, 0, 115, 0, 119, 0, 111, 0, 114, 0, 100, 0]
Same thing using utf8array:
let utf8array = "password".utf8.map({ $0 as UInt8 })
// [112, 97, 115, 115, 119, 111, 114, 100]
So, this is what I did to "fix" it:
var bytesArray:[UInt16] = []
for byte in utf16array {
bytesArray.append(byte)
bytesArray.append(0)
}
print(bytesArray)
// [112, 0, 97, 0, 115, 0, 115, 0, 119, 0, 111, 0, 114, 0, 100, 0]
But I'm sure this is not the right way. Any suggestions?
You can get a representation as UTF-16LE data with
let password = "password€"
let data = password.data(using: .utf16LittleEndian)!
print(data as NSData)
// <70006100 73007300 77006f00 72006400 ac20>
That would already be sufficient to compute the SHA1 digest (code
from How to crypt string to sha1 with Swift?):
var digest = [UInt8](repeating: 0, count:Int(CC_SHA1_DIGEST_LENGTH))
data.withUnsafeBytes {
_ = CC_SHA1($0, CC_LONG(data.count), &digest)
}
let hexEncodedDigest = digest.map { String(format: "%02hhx", $0) }.joined()
print(hexEncodedDigest)
// 177f0d080dfe533e102dd67d6321204813cf1b0c
But if you need it as a byte array then
let bytesArray = data.map { $0 }
print(bytesArray)
// [112, 0, 97, 0, 115, 0, 115, 0, 119, 0, 111, 0, 114, 0, 100, 0, 172, 32]
would work.
(I have appended a non-ASCII characters for demonstration,
€ = U+20AC becomes 172, 32.)
If you are curious how to convert the [UInt16] array to an
[UInt8] array, this is how you could do it with some pointer juggling
(and just a single copy):
let utf16array = Array("password€".utf16)
print(utf16array)
// [112, 97, 115, 115, 119, 111, 114, 100, 8364]
let bytes = Array(utf16array.withUnsafeBufferPointer {
$0.baseAddress!.withMemoryRebound(to: UInt8.self, capacity: 2 * utf16array.count) {
UnsafeBufferPointer(start: $0, count: 2 * utf16array.count)
}
})
print(bytes)
// [112, 0, 97, 0, 115, 0, 115, 0, 119, 0, 111, 0, 114, 0, 100, 0, 172, 32]
What about using the cString accessor?
var bytes = str.cStringUsingEncoding(NSUTF16LittleEndianStringEncoding)
Using the String to Data method data(using:) is the fit for purpose solution here.
But for the fun of it, an alternative making use of the String:s UTF-16 encoding approach (utf16 property of String) of the OP. Using the init(truncatingBitPattern: UInt16) initializer of UInt8, in combination with zip followed by a flatMap, the latter flattening the zipped tuples into an array:
let pw = "password€"
let bytes = zip(pw.utf16.map{ UInt8(truncatingBitPattern: $0) },
pw.utf16.map{ UInt8(truncatingBitPattern: $0 >> 8) })
.flatMap{ [$0, $1] }
print(bytes)
// [112, 0, 97, 0, 115, 0, 115, 0, 119, 0, 111, 0, 114, 0, 100, 0, 172, 32]
I have two RDD's, for example:
firstmapRDD - (0-14,List(0, 4, 19, 19079, 42697, 444, 42748))
secondmapRdd-(0-14,List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94))
I want to find the intersection.
I tried, var interResult = firstmapRDD.intersection(secondmapRdd), which shows no result in output file.
I also tried , cogrouping based on keys, mapRDD.cogroup(secondMapRDD).filter(x=>), but I don't know how to find the intersection between both the values, is it x=>x._1.intersect(x._2), Can someone help me with the syntax?
Even this throws a compile time error, mapRDD.cogroup(secondMapRDD).filter(x=>x._1.intersect(x._2))
var mapRDD = sc.parallelize(map.toList)
var secondMapRDD = sc.parallelize(secondMap.toList)
var interResult = mapRDD.intersection(secondMapRDD)
It may be because of ArrayBuffer[List[]] values, because of which the intersection is not working. Is there any hack to remove it?
I tried doing this
var interResult = mapRDD.cogroup(secondMapRDD).filter{case (_, (l,r)) => l.nonEmpty && r.nonEmpty }. map{case (k,(l,r)) => (k, l.toList.intersect(r.toList))}
Still getting an empty list!
Since you are looking intersect on values, you need to join both RDDs, get all the matched values, then do the intersect on values.
sample code:
val firstMap = Map(1 -> List(1,2,3,4,5))
val secondMap = Map(1 -> List(1,2,5))
val firstKeyRDD = sparkContext.parallelize(firstMap.toList, 2)
val secondKeyRDD = sparkContext.parallelize(secondMap.toList, 2)
val joinedRDD = firstKeyRDD.join(secondKeyRDD)
val finalResult = joinedRDD.map(tuple => {
val matchedLists = tuple._2
val intersectValues = matchedLists._1.intersect(matchedLists._2)
(tuple._1, intersectValues)
})
finalResult.foreach(println)
The output will be
(1,List(1, 2, 5))
In the context of another stackoverflow question, I have this snippet:
def orderedGroupBy[T, P](seq: Traversable[T], f: T => P): Traversable[Tuple2[P, Traversable[T]]] = {
#tailrec
def accumulator(seq: Traversable[T], f: T => P, res: List[Tuple2[P, Traversable[T]]]): Traversable[Tuple2[P, Traversable[T]]] = seq.headOption match {
case None => res.reverse
case Some(h) => {
val key = f(h)
val subseq = seq.takeWhile(f(_) == key)
accumulator(seq.drop(subseq.size), f, (key -> subseq) :: res)
}
}
accumulator(seq, f, Nil)
}
I'd like to use it just like one can use .groupBy, e.g.:
orderedGroupBy(1 to 100, (_ / 10))
But the compiler yields an error about not having enough type info
<console>:10: error: missing parameter type for expanded function ((x$1) => x$1.$div(10))
orderedGroupBy(1 to 100, (_ / 10))
What is the idiomatic way to do this?
You can curry the parameters, so that T is inferred solely from seq: Traversable[T].
def orderedGroupBy[T, P](seq: Traversable[T])(f: T => P): Traversable[Tuple2[P, Traversable[T]]] = ???
scala> orderedGroupBy(1 to 100)(_ / 10)
res110: Traversable[(Int, Traversable[Int])] = List((0,Range(1, 2, 3, 4, 5, 6, 7, 8, 9)), (1,Range(10, 11, 12, 13, 14, 15, 16, 17, 18, 19)), (2,Range(20, 21, 22, 23, 24, 25, 26, 27, 28, 29)), (3,Range(30, 31, 32, 33, 34, 35, 36, 37, 38, 39)), (4,Range(40, 41, 42, 43, 44, 45, 46, 47, 48, 49)), (5,Range(50, 51, 52, 53, 54, 55, 56, 57, 58, 59)), (6,Range(60, 61, 62, 63, 64, 65, 66, 67, 68, 69)), (7,Range(70, 71, 72, 73, 74, 75, 76, 77, 78, 79)), (8,Range(80, 81, 82, 83, 84, 85, 86, 87, 88, 89)), (9,Range(90, 91, 92, 93, 94, 95, 96, 97, 98, 99)), (10,Range(100)))