From what I understand of ActionScript, there are two kinds of casts:
var bar0:Bar = someObj as Bar; // "as" casting
var bar1:Bar = Bar(someObj); // "class name" casting (for want of a better name)
Also, and please correct me if I'm wrong here, as casting will either return an instance of the class or null, while "class name" casting will either return an instance of the class or raise an exception if the cast is impossible – other than this, they are identical.
Given this, though, as casting seems to be a massive violation of the fail-fast-fail-early principle... And I'm having trouble imagining a situation where it would be preferable to use an as cast rather than a class name cast (with, possibly, an instanceof thrown in there).
So, my question is: under what circumstances would it be preferable to use as casting?
There are a couple of points in this discussion worth noting.
There is a major difference in how the two work, Class() will attempt to cast the object to the specified Class, but on failure to do so will (sometimes, depends on datatype) throw a runtime error. On the other hand using object as Class will preform a type check first, and if the specified object cannot be cast to the indicated Class a null value is returned instead.
This is a very important difference, and is a useful tool in development. It allows us to do the following:
var o:MyClass = myArray[i] as MyClass;
if(o)
{
//do stuff
}
I think the usefulness of that is pretty obvious.
"as" is also more consistent with the rest of the language (ie: "myObject is MyClass").
The MyClass() method has additional benefits when working with simple data types (int, Number, uint, string) Some examples of this are:
var s:String = "89567";
var s2:String = "89 cat";
var n:Number = 1.9897;
var i:int = int(s); // i is = 89567, cast works
var i2:int = int(s2); //Can't convert so i2 is set to 0
var i3:int = int(n); // i = 1
var n2:Number = Number(s2); // fails, n2 = NaN
//when used in equations you'll get very different results
var result:int = int(n) * 10; //result is 10
var result:int = n * 10; //result is 19.89700
var result:int = int(s2) * 10; //result is 0
trace(s2 as Number); //outputs null
trace(s2 as int); //outputs null
trace(Number(s2)); //outputs NaN
This is a good and important topic, as a general rule I use "as" when working with Objects and Cast() when using simpler data types, but that's just how I like to structure my code.
You need to use as to cast in two scenarios: casting to a Date, and casting to an Array.
For dates, a call to Date(xxx) behaves the same as new Date().toString().
For arrays, a call to Array(xxx) will create an Array with one element: xxx.
The Class() casting method has been shown to be faster than as casting, so it may be preferable to as when efficiency matters (and when not working with Dates and Arrays).
import flash.utils.*;
var d = Date( 1 );
trace( "'" + d, "'is type of: ",getQualifiedClassName( d ) );
var a:Array = Array( d );
trace( "'" + a, "' is type of: ", getQualifiedClassName( a ) );
//OUTPUT
//'Mon Jun 15 12:12:14 GMT-0400 2009 'is type of: String
//'Mon Jun 15 12:12:14 GMT-0400 2009 ' is type of: Array
//COMPILER ERRORS/WARNINGS:
//Warning: 3575: Date(x) behaves the same as new Date().toString().
//To cast a value to type Date use "x as Date" instead of Date(x).
//Warning: 1112: Array(x) behaves the same as new Array(x).
//To cast a value to type Array use the expression x as Array instead of Array(x).
`
They actually do different things...when you say
myvar as ClassName
You are really just letting the compiler know that this object is either a ClassName or a subclass of ClassName
when you say:
ClassName(myvar)
It actually tries to convert it to that type of object.
so if your object is a or a descent of the class and you do not need to convert it you would use as
examples:
var myvar:String = '<data/>';
var othervar:XML = XML(myvar); //right
var myvar:String = '<data/>';
var othervar:XML = (myvar as XML); //wrong
var myvar:XML = <data/>;
var othervar:XML = myvar as XML; // right
Use 'as' with arrays.
var badArray:Array;
badArray = Array(obj);
Will yield an array of length one with the original array in the first element. If you use 'as' as follows, you get the exptected result.
var goodArray:Array;
goodArray = obj as Array;
Generally, 'as' is preferable to 'Class()' in ActionScript as it behaves more like casting in other languages.
I use it when I have an ArrayCollection of objects and need to enumerate through them, or use a selector function.
e.g.
var abc:mytype = mycollection.getItemAt(i) as mytype
Related
I am trying to pass some random integers (which I have stored in an array) to my hardware as an Input through the poke method in peekpoketester. But I am getting this error:
chisel3.internal.ChiselException: Error: Not in a UserModule. Likely cause: Missed Module() wrap, bare chisel API call, or attempting to construct hardware inside a BlackBox.
What could be the reason? I don't think I need a module wrap here as this is not hardware.
class TesterSimple (dut: DeviceUnderTest)(parameter1 : Int)(parameter2 : Int) extends
PeekPokeTester (dut) {
var x = Array[Int](parameter1)
var y = Array[Int](parameter2)
var z = 1
poke(dut.io.IP1, z.asUInt)
for(i <- 0 until parameter1){poke(dut.io.IP2(i), x(i).asUInt)}
for(j <- 0 until parameter2){poke(dut.io.IP3(j), y(j).asUInt)}
}
object TesterSimple extends App {
implicit val parameter1 = 2
implicit val parameter2 = 2
chisel3.iotesters.Driver (() => DeviceUnderTest(parameter1 :Int, parameter2 :Int)) { c =>
new TesterSimple (c)(parameter1, parameter2)}
}
I'd suggest a couple of things.
Main problem, I think you are not initializing your arrays properly
Try using Array.fill or Array.tabulate to create and initialize arrays
val rand = scala.util.Random
var x = Array.fill(parameter1)(rand.nextInt(100))
var y = Array.fill(parameter2)(rand.nextInt(100))
You don't need the .asUInt in the poke, it accepts Ints or BigInts
When defining hardware constants, use .U instead of .asUInt, the latter is a way of casting other chisel types, it does work but it a backward compatibility thing.
It's better to not start variables or methods with capital letters
I suggest us class DutName(val parameter1: Int, val parameter2: Int) or class DutName(val parameter1: Int)(val parameter2: Int) if you prefer.
This will allow to use the dut's paremeters when you are writing your test.
E.g. for(i <- 0 until dut.parameter1){poke(dut.io.IP2(i), x(i))}
This will save you have to duplicate parameter objects on your DUT and your Tester
Good luck!
Could you also share your DUT?
I believe the most likely case is your DUT does not extend Module
My goal is to create some kind of Parser to parse string formulas, similar to Excel formulas.
Formula string example (barcode example) -
"CONCAT('98', ZEROFILL([productNumber],5,'0'), ZEROFILL(EQUATION([weightKG]*1000),5,'0'))"
where
'98' - String
[productNumber] and [weightKG] - are variables that can be changed
CONCAT, ZEROFILL and EQUATION are methods which exist in class
For this formula with variables [productNumber] = '1' and [weightKG] = 0.1 result must be
'980000100100'
The question is how to split/parse whole string to parts and detect methods, variables and string values?
Another idea occurred, while i was typing - is to store whole formula in XML format.
Thank You.
You can use String.split() to get an array of substrings.
However, using your example, calling split(",") would give you the following array:
[0]=CONCAT('98'
[1]= ZEROFILL([productNumber]
[2]=5
[3]='0')
[4]= ZEROFILL(EQUATION([weightKG]*1000)
[5]=5
[6]='0'))
That doesn't seem like it will be very helpful for your project. Instead, you might think about creating a parse() function with some logic to find useful substrings:
function parse(input:String):Array {
var firstParen:int = input.indexOf("(");
var lastParen:int = input.lastIndexOf(")");
var formulaName:String = input.substring(0, firstParen);
var arguments:String = input.substring(firstParen, lastParen);
var argumentList:Array = parseArgs(arguments);
var result:Array = new Array();
result.push(formulaName);
//Recursively call parse() on the argumentList
foreach (var elem:* in argumentList) {
result.push(elem); //Could be string or array.
}
}
function parseArgs(input:String):Array {
// Look for commas that aren't enclosed inside parenthesis and
// construct an array of substrings based on that.
//A regex may be helpful here, but the implementation is left
//as an exercise for the reader.
}
My code:
var dict = new Dictionary();
dict[[1, 2]] = 1;
var dbg = dict[[1, 2]];
trace(dbg);
Output:
undefined
Why?
How can I get
set<pair<int, int> >
from C++?
Note: I would not call [1,2] "pair of int", it is "array with 2 elements". { item1:1, item2:2 } would look more like pair to me.
According to documentation Dictionary uses strict equals (===) to compare keys, so passing new array as key every time will not work for indexing (arrays are strictly equal only when it is exactly the same array, not an array with the same content).
Depending on your needs converting key to a string maybe good option:
var keyPair = [1,2];
var key = keyPair[0] + "_" + keyPair[1];
I will run a set of experiments. The main method evaluated has the following signature:
[Model threshold] = detect(...
TrainNeg, TrainPos, nf, nT, factors, ...
removeEachStage, applyEstEachStage, removeFeatures);
where removeEachStage, applyEstEachStage, and removeFeatures are booleans. You can see that if I reverse the order of any of these boolean parameters I may get wrong results.
Is there a method in MATLAB that allows better organization in order to minimize this kind of error? Or is there any tool I can use to protect me against these errors?
Organization with a struct
You could input a struct that has these parameters as it's fields.
For example a structure with fields
setts.TrainNeg
.TrainPos
.nf
.nT
.factors
.removeEachStage
.applyEstEachStage
.removeFeatures
That way when you set the fields it is clear what the field is, unlike a function call where you have to remember the order of the parameters.
Then your function call becomes
[Model threshold] = detect(setts);
and your function definition would be something like
function [model, threshold] = detect(setts)
Then simply replace the occurrences of e.g. param with setts.param.
Mixed approach
You can also mix this approach with your current one if you prefer, e.g.
[Model threshold] = detect(in1, in2, setts);
if you wanted to still explicitly include in1 and in2, and bundle the rest into setts.
OOP approach
Another option is to turn detect into a class. The benefit to this is that a detect object would then have member variables with fixed names, as opposed to structs where if you make a typo when setting a field you just create a new field with the misspelled name.
For example
classdef detect()
properties
TrainNeg = [];
TrainPos = [];
nf = [];
nT = [];
factors = [];
removeEachStage = [];
applyEstEachStage = [];
removeFeatures =[];
end
methods
function run(self)
% Put the old detect code in here, use e.g. self.TrainNeg to access member variables (aka properties)
end
end
I have a table called Subjects,
I have an another Table called Allocations, which stores the Allocations of the Subjects
I have a Datagridview, which is populated with Subject Allocations from the Allocations Table
Now i need to get the Subjects that are not in the Datagridview
To do this
I Get All Subjects from the ObjectContext
Now i get all the Subjects that are alloted from the Datagridview (It Returns me an InMemory Collection)
Now i use the LINQ.EXCEPT method to filter the results, but it is throwing me the Following Exception,
"Unable To Create Constant Value of Type "ObjectContext.Subjects" Only primitive types ('such as Int32, String, and Guid') are supported in this context."
Below is my Code
public static IOrderedQueryable<Subject> GetSubjects()
{
return OBJECTCONTEXT.Subjects.OrderBy(s => s.Name);
}
private IQueryable<Subject> GetAllocatedSubjectsFromGrid()
{
return (from DataGridViewRow setRow in dgv.Rows
where !setRow.IsNewRow
select setRow.DataBoundItem).Cast<Allocation>() //I know the Problem lies somewhere in this Function
.Select(alloc =>alloc.Subject).AsQueryable();
}
private void RUN()
{
IQueryable<Subject> AllSubjects = GetSubjects(); //Gets
IQueryable<Subject> SubjectsToExclude = GetAllocatedSubjectsFromGrid();
IQueryable<Subject> ExcludedSubjects = AllSubjects.Except(SubjectsToExclude.AsEnumerable());
//Throwing Me "Unable to create a constant value of type 'OBJECTCONTEXT.Subject'. Only primitive types ('such as Int32, String, and Guid') are supported in this context."
}
As a result of googling i found that it happens because LINQ can't compare between InMemory collection(Records from DGV) and Objectcontext(FromDB)
A little short of time, have not tested it. But I guess you can try to get it all in memory. So instead of using
IQueryable<Subject> AllSubjects = GetSubjects(); //Gets
You do
List<Subject> AllSubjects = GetSubjects().ToList(); //
List<Subject> SubjectsToExclude = GetAllocatedSubjectsFromGrid().ToList();
List<Subject> ExcludedSubjects = AllSubjects.Except(SubjectsToExclude);
I got around this by comparing keys in a Where clause rather than using Except.
So instead of:
var SubjectsToExclude = GetAllocatedSubjectsFromGrid();
var ExcludedSubjects = AllSubjects.Except(SubjectsToExclude.AsEnumerable());
Something more like:
var subjectsToExcludeKeys =
GetAllocatedSubjectsFromGrid()
.Select(subject => subject.ID);
var excludedSubjects =
AllSubjects
.Where(subject => !subjectsToExcludeKeys.Contains(subject.ID));
(I'm guessing what your entity's key looks like though.)
This allows you to keep everything in Entity Framework, rather than pulling everything into memory.