I have a map called:
std::unordered_map < std::string, struct > g_users
but I would like to enter a second key, so that I could work with:
std::unordered_map < std::pair < std::string, int> struct> g_users
Is there any way of using the find function just to look for one of the keys? If not, is there any way to filter my map according to two keys?
Related
I have, tab=Array(1.U, 6.U, 5.U, 2.U, 4.U, 3.U) and Y=Seq(b,g,g,g,b,g), tab is an array of UInt.
I want to do a map on tab as follows:
tab.map(case idx=>Y(idx))
But I keep getting the error: found chisel3.core.UInt, required Int.
I tried using the function peek() to convert idx to an Int by doing
tab.map(case idx=>Y(peek(idx).toInt)
but I get peek not found. I also saw that I cannot convert a chisel UInt to an Int here but did not understand the use of peek well with the example given. So please, is there another approach to do the above?
Thanks!
The immediate problem is that you cannot access the elements of scala collections using a hardware construct like UInt or SInt. It should work if you wrap Y in a Vec. Depending on your overall module this would probably look like
val YVec = VecInit(Y)
val mappedY = tab.map { case idx => YVec(idx) }
Is there any way to initialize a Sequential value not in one fellow swoop?
Like, can I declare it, then use a for loop to populate it, step by step?
As this could all happen inside a class body, the true immutability of the Sequential value could then kick in once the class instance construction phase has been completed.
Example:
Sequential<String> strSeq;
for (i in span(0,10)) {
strSeq[i] = "hello";
}
This code doesn't work, as I get this error:
Error:(12, 9) ceylon: illegal receiving type for index expression:
'Sequential' is not a subtype of 'KeyedCorrespondenceMutator' or
'IndexedCorrespondenceMutator'
So what I can conclude is that sequences must be assigned in one statement, right?
Yes, several language guarantees hinge on the immutability of sequential objects, so that immutability must be guaranteed by the language – it can’t just trust you that you won’t mutate it after the initialization is done :)
Typically, what you do in this situation is construct some sort of collection (e. g. an ArrayList from ceylon.collection), mutate it however you want, and then take its .sequence() when you’re done.
Your specific case can also be written as a comprehension in a sequential literal:
String[] strSeq = [for (i in 0..10) "hello"];
The square brackets used to create a sequence literal accept not only a comma-separated list of values, but also a for-comprehension:
String[] strSeq = [for (i in 0..10) "hello"];
You can also do both at the same time, as long as the for-comprehension comes last:
String[] strSeq = ["hello", "hello", for (i in 0..8) "hello"];
In this specific case, you could also do this:
String[] strSeq = ["hello"].repeat(11);
You can also get a sequence of sequences via nesting:
String[][] strSeqSeq = [for (i in 0..2) [for (j in 0..2) "hello"]];
And you can do the cartesian product (notice that the nested for-comprehension here isn't in square brackets):
[Integer, Character][] pairs = [for (i in 0..2) for (j in "abc") [i, j]];
Foo[] is an abbreviation for Sequential<Foo>, and x..y translates to span(x, y).
If you know upfront the size of the sequence you want to create, then a very efficient way is to use an Array:
value array = Array.ofSize(11, "");
for (i in 0:11) {
array[i] = "hello";
}
String[] strSeq = array.sequence();
On the other hand, if you don't know the size upfront, then, as described by Lucas, you need to use either:
a comprehension, or
some sort of growable array, like ArrayList.
How can I perform the following operations on a dictionary, provided all my values are unique and unsorted.
key : value
152 : 780
87 : 688
2165 : 15
I want to get all keys.
I want to find key for value 688
I want to get all values.
Preferably, without a loop and without having to maintain the key-value relation in an external object.
I sometimes miss, python for these sort of things.
If the keys are integer values, Array might help. It is a sparse array; so for and for each will only process keys that have been assigned a value (I have no idea about memory usage though).
So:
var list: Array = [];
list[1] = 10;
list[4] = 40;
for each(var value: int in list) trace(value);
// outputs (order can be different)
// 10
// 40
// index has to be * or String; the compiler gives an error if it is not
for(var index: * in list) trace(index);
// outputs (order can be different)
// 1
// 4
There is a indexOf method to get the key for a value; there is no simple function to get all keys though.
You cannot do any point you want without the cost of an iteration over your Dictionary. So maintaining another object seems to be what you need to do.
I'm reading a simple CSV file with Filehelpers - the file is just a key, value pair. (string, int64)
The f# type I've written for this is:
type MapVal (key:string, value:int64) =
new()= MapVal("",0L)
member x.Key = key
member x.Value = value
I'm missing something elementary here, but FileHelpers always assumes the order of fields to be the reverse of what I've specified - as in Value, Key.
let dfe = new DelimitedFileEngine(typeof<MapVal>)
let recs = dfe.ReadFile(#"D:\e.dat")
recs |> Seq.length
What am I missing here?
The order of primary constructor parameters doesn't necessarily determine the order that fields occur within a type (in fact, depending on how the parameters are used, they may not even result in a field being generated). The fact that FileHelpers doesn't provide a way to use properties instead of fields is unforunate, in my opinion. If you want better control over the physical layout of the class, you'll need to declare the fields explicitly:
type MapVal =
val mutable key : string
val mutable value : int64
new() = { key = ""; value = 0L }
new(k, v) = { key = k; value = v }
member x.Key = x.key
member x.Value = x.value
The library uses the order of the field in the declaration, but looks like that F# words different, in the last the last stable version of the library you can use the [FieldOrder(1)] attribute to provide the order of the fields.
http://teamcity.codebetter.com/viewLog.html?buildId=lastSuccessful&buildTypeId=bt66&tab=artifacts&guest=1
Cheers
I'm trying to define a new type and have not had much luck finding any information about using lists within them. Basically my new type will contain two lists, lets say x and y of type SqlSingle (the user defined type is written in C#) is this even possible?
If not how are you supposed to go about simulating a two lists of an arbitary length in an SQL Server 2008 column?
I'm possibly going about this the wrong way but it is the best approach I can think of at the moment. Any help is very much appreciated.
You can use a List<T> in a CLR UDT - although CLR types are structs, which should be immutable, so a ReadOnlyCollection<T> would be a better choice if you don't have a very compelling reason for the mutability. What you need to know in either case is that SQL won't know how to use the list itself; you can't simply expose the list type as a public IList<T> or IEnumerable<T> and be on your merry way, like you would be able to do in pure .NET.
Typically the way to get around this would be to expose a Count property and some methods to get at the individual list items.
Also, in this case, instead of maintaining two separate lists of SqlSingle instances, I would create an additional type to represent a single point, so you can manage it independently and pass it around in SQL if you need to:
[Serializable]
[SqlUserDefinedType(Format.Native)]
public struct MyPoint
{
private SqlSingle x;
private SqlSingle y;
public MyPoint()
{
}
public MyPoint(SqlSingle x, SqlSingle y) : this()
{
this.x = x;
this.y = y;
}
// You need this method because SQL can't use the ctors
[SqlFunction(Name = "CreateMyPoint")]
public static MyPoint Create(SqlSingle x, SqlSingle y)
{
return new MyPoint(x, y);
}
// Snip Parse method, Null property, etc.
}
The main type would look something like this:
[Serializable]
[SqlUserDefinedType(Format.UserDefined, IsByteOrdered = true, MaxByteSize = ...)]
public struct MyUdt
{
// Make sure to initialize this in any constructors/builders
private IList<MyPoint> points;
[SqlMethod(OnNullCall = false, IsDeterministic = true, IsPrecise = true)]
public MyPoint GetPoint(int index)
{
if ((index >= 0) && (index < points.Count))
{
return points[index];
}
return MyPoint.Null;
}
public int Count
{
get { return points.Count; }
}
}
If you need SQL to be able to get a sequence of all the points, then you can add an enumerable method to the sequence type as well:
[SqlFunction(FillRowMethodName = "FillPointRow",
TableDefinition = "[X] real, [Y] real")]
public static IEnumerable GetPoints(MyUdt obj)
{
return obj.Points;
}
public static void FillPointRow(object obj, out SqlSingle x, out SqlSingle y)
{
MyPoint point = (MyPoint)obj;
x = point.X;
y = point.Y;
}
You might think that it's possible to use an IEnumerable<T> and/or use an instance method instead of a static one, but don't even bother trying, it doesn't work.
So the way you can use the resulting type in SQL Server is:
DECLARE #UDT MyUdt
SET #UDT = <whatever>
-- Will show the number of points
SELECT #UDT.Count
-- Will show the binary representation of the second point
SELECT #UDT.GetPoint(1) AS [Point]
-- Will show the X and Y values for the second point
SELECT #UDT.GetPoint(1).X AS [X], #UDT.GetPoint(1).Y AS [Y]
-- Will show all the points
SELECT * FROM dbo.GetPoints(#UDT)
Hope this helps get you on the right track. UDTs can get pretty complicated to manage when they're dealing with list/sequence data.
Also note that you'll obviously need to add serialization methods, builder methods, aggregate methods, and so on. It can be quite an ordeal; make sure that this is actually the direction you want to go in, because once you start adding UDT columns it can be very difficult to make changes if you realize that you made the wrong choice.
Lists as you describe are usually normalized - that is, stored in separate tables with one row per item - rather than trying to cram them into a single column. If you can share more info on what you are trying to accomplish, maybe we can offer more assistance.
Edit - suggested table structure:
-- route table--
route_id int (PK)
route_length int (or whatever)
route_info <other fields as needed>
-- waypoint table --
route_id int (PK)
sequence tinyint (PK)
lat decimal(9,6)
lon decimal(9,6)
waypoint_info <other fields as needed>