I'm having a validate method that return a boolean.
I'm invoking this method (Java 7) as follow:
boolean isValid = true;
for (String key: aMap.keySet()) {
isValid &= validate(key, aMap.get(key));
if(!isValid) {
break;
}
}
I would like to rewrite this code in Java 8.
Java 8 allows iterating across a Map using:
aMap.forEach((k,v) -> validate(k, v));
But this won't work:
aMap.forEach((k,v) -> isValid &= validate(k, v));
Question
How can I rewrite the the Java 7 code into Java 8 to achieve the same result?
Note
Raised a similar question here (but this time, for the iteration to continue through all the Map elements)
boolean isValid = aMap.keySet()
.stream()
.allMatch(key -> validate(key, paramRow.getRowMap().get(colName))
As a side note, what does paramRow.getRowMap().get(colName) do? And where do you get colName? May be you don't have to recompute this for every single key
Related
I'm following tutorial from the official Microsoft learning page (https://learn.microsoft.com/en-us/azure/quantum/tutorial-qdk-explore-entanglement?pivots=ide-azure-portal) about quantum entanglement.
Basically, I copied an example posted there and I am getting error:
QS5026 The variable "numOnesQ1" cannot be reassigned here. In conditional blocks that depend on a measurement result, the target QuantinuumProcessor only supports reassigning variables that were declared within the block.
I understand what it says but it's just a copy from the official Microsoft tutorial. Am I missing something simple like imports, wrong settings? If not, how can I in other way set variables declared outside conditional blocks that depend on a measurement result?
Here is my code:
namespace Quantum.QuantumDream {
open Microsoft.Quantum.Canon;
open Microsoft.Quantum.Intrinsic;
operation GetRandomResult() : Result {
use q = Qubit();
H(q);
return M(q);
}
#EntryPoint()
operation TestBellState(count : Int, initial : Result) : (Int, Int, Int, Int) {
mutable numOnesQ1 = 0;
mutable numOnesQ2 = 0;
// allocate the qubits
use (q1, q2) = (Qubit(), Qubit());
for test in 1..count {
SetQubitState(initial, q1);
SetQubitState(Zero, q2);
// measure each qubit
let resultQ1 = M(q1);
let resultQ2 = M(q2);
// Count the number of 'Ones':
if resultQ1 == One {
set numOnesQ1 += 1;
}
if resultQ2 == One {
set numOnesQ2 += 1;
}
}
// reset the qubits
SetQubitState(Zero, q1);
SetQubitState(Zero, q2);
// Return number of |0> states, number of |1> states
Message("q1:Zero, One q2:Zero, One");
return (count - numOnesQ1, numOnesQ1, count - numOnesQ2, numOnesQ2 );
}
operation SetQubitState(desired : Result, target : Qubit) : Unit {
if desired != M(target) {
X(target);
}
}
}
This tutorial code is only supposed to run on a local simulator (using %simulate magic commands in a Jupyter Notebook). From the error message, it looks like you've tried to run it on one of Quantinuum targets, which have some limitations on the kinds of things you can do in the code. To run equivalent code on Quantinuum, you'd need to define an operation for just the body of the loop (preparing a state and measuring it) and run it as a job - the cloud targets will take care of the loop themselves, running your code multiple times and returning to you a histogram of the results. For an example, you can see the QRNG sample in the samples gallery in Azure Portal.
I am new to Flink CEP and have been playing around with the patterns for better understanding of them.
I have a simple case of a "begin" & a followedBy".
I notice that in the case of followedBy, the same event is looping through it multiple times.
What am I missing here?
Pattern match_win = Pattern.begin("first").where(new SimpleCondition() {
public boolean filter(HitDTO hitDTO) throws Exception {
boolean result = false;
if (hitDTO.getHitScore() == 4)
{
System.out.println("First:" + hitDTO + ": " + hitDTO.getHitScore());
result = true;
}
return result;
}
}).followedBy("next").where(new SimpleCondition<HitDTO>(){
public boolean filter(HitDTO hitDTO) throws Exception
{
boolean result = false;
if (hitDTO.getHitScore() == 6)
{
System.out.println("Next:" + hitDTO+ ": " + hitDTO.getHitScore());
result = true;
}
return result;
}
});
I am passing in 4,4,6
Parallelism is set at 1.
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment().setParallelism(1);
However, this is what I see in the logs for the printout within the patterns, where 6 is looping 4 times when it was passed in only once.
First:com.rs.dto.HitDTO#17619295: 4
First:com.rs.dto.HitDTO#c108f70: 4
Next:com.rs.dto.HitDTO#5d13aab8: 6
Next:com.rs.dto.HitDTO#5d13aab8: 6
Next:com.rs.dto.HitDTO#5d13aab8: 6
Next:com.rs.dto.HitDTO#5d13aab8: 6
Just wondering why the same event is looping through multiple times but the outcome is correct.
Thanks for your answer.
It is normal that the process of attempting to match a pattern to an input sequence will involve multiple evaluations of various components of the pattern. That's how pattern matching works: the pattern is compiled to a finite state machine, and all possible paths the input might take through that FSM are considered, looking for paths that lead to the terminal, matching state. If you're not careful in how you define your pattern, this can lead to a combinatorial explosion of effort.
I want to be able to modify my array of objects using map in Swift of the fly, without looping through each element.
Before here were able to do something like this (Described in more details here:
gnomes = gnomes.map { (var gnome: Gnome) -> Gnome in
gnome.age = 140
return gnome
}
Thanks for Erica Sadun and others, new proposals have gone through and we're now getting rid of C-style loops and using var inside the loop.
In my case I'm first getting a warning to remove the var in then an error my gnome is a constant (naturally)
My question is : How do we alter arrays inside a map or the new styled loops for that matter to be fully prepared for Swift 3.0?
If you want to keep that syntax, just use a (mutable) temporary variable
gnomes = gnomes.map { (gnome: Gnome) -> Gnome in
var mutableGnome = gnome
mutableGnome.age = 140
return mutableGnome
}
(Below follows the case where Gnome is a reference type; a class -- since you haven't showed us how you've defined Gnome. For the case where Gnome as value type (a struct), see #vadian:s answer)
The removal of var will not effect using .map to mutate mutable members of an array of reference type objects. I.e., you could simply use your old approach (omitting however, the var in the .map closure signature).
class Gnome {
var age = 42
}
var gnomes = [Gnome(), Gnome(), Gnome()]
gnomes = gnomes.map {
$0.age = 150
return $0
}
/* result */
gnomes.forEach { print($0.age) } // 3x 150
However, in case you just want to modify your original array rather than assigning the result of .map to a new array, .forEach might be a more appropriate choice than .map.
gnomes.forEach { $0.age = 140 }
/* result */
gnomes.forEach { print($0.age) } // 3x 140
Given:
struct Gnome {
var age: Int = 0
}
var gnomes = Array(count: 5, repeatedValue: Gnome())
... there are two decent options. The first is as #vadian put it:
gnomes = gnomes.map{
var gnome = $0
gnome.age = 70
return gnome
}
Whilst the second keeps control over "ageing" private and simplifies mapping at the point of call:
struct Gnome {
private(set) var age: Int = 0
func aged(age: Int) -> Gnome {
var gnome = self
gnome.age = age
// any other ageing related changes
return gnome
}
}
gnomes = gnomes.map{ $0.aged(140) }
Of course, reference types still have their place in programming, which may well be a better fit in this case. The friction we are experiencing here suggests that we are trying to treat these structures as if they were objects. If that is the behaviour you need, then you should consider implementing Gnome as a class.
I have the following code:
public fun findSomeLikeThis(): ArrayList<T>? {
val result = Db4o.objectContainer()!!.queryByExample<T>(this as T) as Collection<T>
if (result == null) return null
return ArrayList(result)
}
If I call this like:
var list : ArrayList<Person>? = p1.findSomeLikeThis()
for (p2 in list) {
p2.delete()
p2.commit()
}
It would give me the error:
For-loop range must have an 'iterator()' method
Am I missing something here?
Your ArrayList is of nullable type. So, you have to resolve this. There are several options:
for (p2 in list.orEmpty()) { ... }
or
list?.let {
for (p2 in it) {
}
}
or you can just return an empty list
public fun findSomeLikeThis(): List<T> //Do you need mutable ArrayList here?
= (Db4o.objectContainer()!!.queryByExample<T>(this as T) as Collection<T>)?.toList().orEmpty()
try
for(p2 in 0 until list.count()) {
...
...
}
I also face this problem when I loop on some thing it is not an array.
Example
fun maximum(prices: Array<Int>){
val sortedPrices = prices.sort()
for(price in sortedPrices){ // it will display for-loop range must have iterator here (because `prices.sort` don't return Unit not Array)
}
}
This is different case to this question but hope it help
This can also happen in Android when you read from shared preferences and are getting a (potentially) nullable iterable object back like StringSet. Even when you provide a default, the compiler is not able to determine that the returned value will never actually be null. The only way I've found around this is by asserting that the returned expression is not null using !! operator, like this:
val prefs = PreferenceManager.getDefaultSharedPreferences(appContext)
val searches = prefs.getStringSet("saved_searches", setOf())!!
for (search in searches){
...
}
Here is code that use this eval method in Dart platform.
This is done via reflection.
runtime/lib/mirrors_impl.dart
_getFieldSlow(unwrapped) {
// ..... Skipped
var atPosition = unwrapped.indexOf('#');
if (atPosition == -1) {
// Public symbol.
f = _eval('(x) => x.$unwrapped', null);
} else {
// Private symbol.
var withoutKey = unwrapped.substring(0, atPosition);
var privateKey = unwrapped.substring(atPosition);
f = _eval('(x) => x.$withoutKey', privateKey);
}
// ..... Skipped
}
static _eval(expression, privateKey)
native "Mirrors_evalInLibraryWithPrivateKey";
runtime/lib/mirrors.cc
DEFINE_NATIVE_ENTRY(Mirrors_evalInLibraryWithPrivateKey, 2) {
GET_NON_NULL_NATIVE_ARGUMENT(String, expression, arguments->NativeArgAt(0));
GET_NATIVE_ARGUMENT(String, private_key, arguments->NativeArgAt(1));
const GrowableObjectArray& libraries =
GrowableObjectArray::Handle(isolate->object_store()->libraries());
const int num_libraries = libraries.Length();
Library& each_library = Library::Handle();
Library& ctxt_library = Library::Handle();
String& library_key = String::Handle();
if (library_key.IsNull()) {
ctxt_library = Library::CoreLibrary();
} else {
for (int i = 0; i < num_libraries; i++) {
each_library ^= libraries.At(i);
library_key = each_library.private_key();
if (library_key.Equals(private_key)) {
ctxt_library = each_library.raw();
break;
}
}
}
ASSERT(!ctxt_library.IsNull());
return ctxt_library.Evaluate(expression);
runtime/vm/bootstrap_natives.h
V(Mirrors_evalInLibraryWithPrivateKey, 2) \
P.S.
I ask question here becuase I cannot ask it at Dart mail lists.
P.S.
As we can see it static private method in mirrors_impl.dart:
static _eval(expression, privateKey) native "Mirrors_evalInLibraryWithPrivateKey";
Does anyone want that this method should be public? (this is not a question but just a thought aloud).
According to the Dart FAQ a pure string eval like that is not likely to make it into the language, even though other dynamic features will likely be added:
So, for example, Dart isn’t likely to support evaluating a string as
code in the current context, but it may support loading that code
dynamically into a new isolate. Dart isn’t likely to support adding
fields to a value, but it may (through a mirror system) support adding
fields to a class, and you can effectively add methods using
noSuchMethod(). Using these features will have a runtime cost; it’s
important to us to minimize the cost for programs that don’t use them.
This area is still under development, so we welcome your thoughts on
what you need from runtime dynamism.