class Character {
construct new(name,life){
_name = name
_life = life
}
name { _name }
life { _life }
}
If the name and life are the same, it should return true otherwise false.
class Character {
construct new(name,life){
_name = name
_life = life
}
name { _name }
life { _life }
==(other){
return _name == other.name &&
_life == other.life
}
}
var player_one = Character.new("Nova",100)
var player_two = Character.new("Mint Hot Chocolate",50)
var player_three = Character.new("Nova",100)
System.print(player_one == player_three) // Output: true
System.print(player_one == player_two) // Output: false
Related
I'm trying to learn how to use Dome and Wren. To do this I've started working on a simple Flappy Bird clone.
The problem I'm having is that I get the error message
Bird does not implement bird_idle
It then points to line 63 in my main class which is shown below:
class Main {
resources=(value){ _resources = value }
bird=(value){ _bird = value }
construct new() {
_resources = Resources.new()
_bird = Bird.new(_resources.birdIdle, _resources.birdFlap, _resources.obstacleTile.width * 2, _resources.obstacleTile.height * 4, 10, 4)
}
init() {}
update() {}
draw(alpha) {
Canvas.cls()
Canvas.draw(_bird.bird_idle, _bird.center.x, _bird.center.y) <-- this is line 63
}
}
var Game = Main.new()
Since I'm new to Wren I don't quite understand what this means seeing as if you look at my bird class below, I should be implementing bird_idle. So what am I doing wrong?
class Bird {
bird_idle=(value){ _bird_idle = value } <-- Right?
bird_flap=(value){ _bird_flap = value }
center=(value){ _center = value }
gravity=(value){ _gravity = value }
force=(value){ _force = value }
velocity=(value){ _velocity = value }
velocityLimit=(value){ _velocityLimit = value }
isGameRunning=(value){ _isGameRunning = value }
construct new(idle, flap, horizontalPosition, verticalPosition, drag, jumpForce) {
_bird_idle = idle
_bird_flap = flap
_center = Vector.new(horizontalPosition + (idle.width * 0.5), verticalPosition + (idle.height*0.5))
_gravity = drag
_force = jumpForce
_velocityLimit = 1000
_isGameRunning = true
}
jump() {
_velocity = -_force
}
isTouchingCeiling() {
var birdTop = _center.y - (_bird_idle.height * 0.5)
if(birdTop < 0) {
return true
}
return false
}
isTouchingGround() {
var birdBottom = _center.y + (_bird_idle.height * 0.5)
if(birdBottom > height) {
return true
}
return false
}
}
You forgot to add the getter:
class Bird {
construct new(idle) {
_bird_idle = idle
}
bird_idle=(value){_bird_idle = value }
bird_idle{_bird_idle} // You need this if you want to access the field _bird_idle.
}
var my_bird = Bird.new("Idle")
my_bird.bird_idle = "Not Idle"
System.print(my_bird.bird_idle) // Output: Not Idle
Any suggestions on how to improve the following code to make it more Functional Programming oriented. Specifically how to remove the MutableList which signifies historical states. There are two data classes: Bank, which represents a riverbank (number of missionaries and number of cannibals currently on the bank) and BankState which represents a historical state of the two banks (the source bank, target bank and boatAtSource - a boolean which indicates whether the boat is currently at the source or target bank). overloaded operator function plus adds missionaries and cannibals to a riverbank and function minus removes them from a riverbank. The boat function is the one which carries the most heft. You can call the following algorithm from fun main (app.kt) as such:
app.kt
fun main(args:Array<String>) {
val source:Bank = Bank(3,3)
val target:Bank = Bank()
source boat target
}
Bank.kt
data class Bank(val missionaries:Int=0,val cannibals:Int=0)
data class BankState(val sourceTarget:Pair<Bank,Bank>,val boatAtSource:Boolean)
operator fun Bank.plus(b:Pair<Int,Int>):Bank = Bank(this.missionaries+b.first,this.cannibals+b.second)
operator fun Bank.minus(b:Pair<Int,Int>):Bank = Bank(this.missionaries-b.first,this.cannibals-b.second)
infix fun Bank.boat(target:Bank):List<BankState> {
val begin = Pair(this,target)
val history = mutableListOf<BankState>(BankState(begin,true))
boat(begin,true,this.missionaries,this.cannibals,history)
return history
}
fun boat(sourceTarget:Pair<Bank,Bank>,
boatAtSource:Boolean,
totalMissionaries:Int,
totalCannibals:Int,
history:MutableList<BankState>):Boolean {
if(sourceTarget.first.cannibals+sourceTarget.second.cannibals==totalCannibals &&
sourceTarget.first.missionaries + sourceTarget.second.missionaries==totalMissionaries &&
sourceTarget.first.cannibals>=0 &&
sourceTarget.first.missionaries>=0 &&
sourceTarget.second.cannibals>=0 &&
sourceTarget.second.missionaries>=0 &&
(sourceTarget.first.missionaries==0 || sourceTarget.first.missionaries>=sourceTarget.first.cannibals) &&
(sourceTarget.second.missionaries==0 || sourceTarget.second.missionaries >= sourceTarget.second.cannibals)) {
if(sourceTarget.second.missionaries==totalMissionaries &&
sourceTarget.second.cannibals==totalCannibals) {
history.forEach(::println)
return true
} else {
val deltas = listOf(Pair(0,1),Pair(1,1),Pair(1,0),Pair(2,0),Pair(0,2))
val comparator = object : Comparator<Pair<Pair<Boolean,Int>,Pair<Bank,Bank>>> {
override fun compare(arg1:Pair<Pair<Boolean,Int>,Pair<Bank,Bank>>,arg2:Pair<Pair<Boolean,Int>,Pair<Bank,Bank>>):Int {
if(arg1.first.first && arg2.first.first) {
return if(arg1.first.second<arg2.first.second) -1 else if(arg1.first.second>arg2.first.second) 1 else 0
} else if(arg1.first.first){
return 1
} else if(arg2.first.first) {
return -1
}
return 0
}
}
val result = deltas.map{
checkNext(it.first,it.second,totalMissionaries,totalCannibals,history,sourceTarget,boatAtSource)
}.maxWith(comparator)
if(result?.first?.first!=null && result.first.first) {
history.add(BankState(result.second,!boatAtSource))
return true;
}
}
}
return false
}
fun checkNext(missionariesDelta:Int,
cannibalsDelta:Int,
totalMissionaries:Int,
totalCannibals:Int,
history:MutableList<BankState>,
sourceTarget:Pair<Bank,Bank>,
boatAtSource:Boolean):Pair<Pair<Boolean,Int>,Pair<Bank,Bank>> {
val nextSrcTgt = if(boatAtSource) Pair(sourceTarget.first-Pair(missionariesDelta,cannibalsDelta),sourceTarget.second+Pair(missionariesDelta,cannibalsDelta))
else Pair(sourceTarget.first+Pair(missionariesDelta,cannibalsDelta),sourceTarget.second-Pair(missionariesDelta,cannibalsDelta))
val bankState:BankState = BankState(nextSrcTgt,!boatAtSource)
if(!history.contains(bankState)) {
history.add(bankState)
val combo2:Boolean = boat(nextSrcTgt,!boatAtSource,totalMissionaries,totalCannibals,history)
val combo2Depth = history.size
history.remove(bankState)
return Pair(Pair(combo2,combo2Depth),nextSrcTgt)
} else {
return Pair(Pair(false,0),nextSrcTgt)
}
}
HTTPSecurity.swift:124:22: Cannot invoke 'SecPolicyCreateSSL' with an argument list of type '(Bool, String?)'
I'm getting the above error when trying to build a project containing this code:
public func isValid(trust: SecTrustRef, domain: String?) -> Bool {
var tries = 0
while(!self.isReady) {
usleep(1000)
tries += 1
if tries > 5 {
return false //doesn't appear it is going to ever be ready...
}
}
var policy: SecPolicyRef
if self.validatedDN {
policy = SecPolicyCreateSSL(true, domain)
} else {
policy = SecPolicyCreateBasicX509()
}
SecTrustSetPolicies(trust,policy)
if self.usePublicKeys {
if let keys = self.pubKeys {
var trustedCount = 0
let serverPubKeys = publicKeyChainForTrust(trust)
for serverKey in serverPubKeys as [AnyObject] {
for key in keys as [AnyObject] {
if serverKey.isEqual(key) {
trustedCount++
break
}
}
}
if trustedCount == serverPubKeys.count {
return true
}
}
} else if let certs = self.certificates {
let serverCerts = certificateChainForTrust(trust)
var collect = Array<SecCertificate>()
for cert in certs {
if let c = SecCertificateCreateWithData(nil,cert) {
collect.append(c)
}
}
SecTrustSetAnchorCertificates(trust,collect)
var result: SecTrustResultType = 0
SecTrustEvaluate(trust,&result)
let r = Int(result)
if r == kSecTrustResultUnspecified || r == kSecTrustResultProceed {
var trustedCount = 0
for serverCert in serverCerts {
for cert in certs {
if cert == serverCert {
trustedCount++
break
}
}
}
if trustedCount == serverCerts.count {
return true
}
}
}
return false
}
This code is from:
https://github.com/mpclarkson/SwiftHTTP/blob/swift-2/HTTPSecurity.swift#L124
Method using old fashion Boolean which is in fact UInt8. Method also use CFString and not String.
Easy solution is following:
policy = SecPolicyCreateSSL(1, domain as CFString)
More sophisticated solution is use extension for Bool:
extension Bool {
var booleanValue : Boolean {
return self ? 1 : 0
}
init(booleanValue : Boolean) {
self = booleanValue == 0 ? false : true
}
}
Then you can use:
policy = SecPolicyCreateSSL(true.booleanValue, domain as CFString)
I'm trying to write following LINQ query using ServiceStack Ormlite.
dbConn.Select<Product>(p => p.IsActive.HasValue && p.IsActive.Value)
Here, Product is my item class and "IsActive" is Nullable Bool property in that class. When this line executes it always throws "InvalidOperationException" with the message
variable 'p' of type '' referenced from scope '', but it is not defined
I tried different variants as following but still same exception result
dbConn.Select<Product>(p => p.IsActive.HasValue == true && p.IsActive.Value == true)
dbConn.Select<Product>(p => p.IsActive != null && p.IsActive.Value == true)
But if I just write
dbConn.Select<Product>(p => p.IsActive.HasValue)
then it works.
I'm puzzled what is the problem? Is this servicestack ormlite issue?
My answer can handle Nullable value like "value" and "HasValue" with servicestack ormlite. And But also with datetime nullable ,like 'createdate.value.Year'.
you must change two place.
modify VisitMemberAccess method:
protected virtual object VisitMemberAccess(MemberExpression m)
{
if (m.Expression != null)
{
if (m.Member.DeclaringType.IsNullableType())
{
if (m.Member.Name == nameof(Nullable<bool>.Value))
return Visit(m.Expression);
if (m.Member.Name == nameof(Nullable<bool>.HasValue))
{
var doesNotEqualNull = Expression.NotEqual(m.Expression, Expression.Constant(null));
return Visit(doesNotEqualNull); // Nullable<T>.HasValue is equivalent to "!= null"
}
throw new ArgumentException(string.Format("Expression '{0}' accesses unsupported property '{1}' of Nullable<T>", m, m.Member));
}
if (m.Member.DeclaringType == typeof(DateTime))
{
var ExpressionInfo = m.Expression as MemberExpression;
if (ExpressionInfo.Member.DeclaringType.IsNullableType())
{
if (ExpressionInfo.Member.Name == nameof(Nullable<bool>.Value))
{
var modelType = (ExpressionInfo.Expression as MemberExpression).Expression.Type;
var tableDef = modelType.GetModelDefinition();
var columnName = (ExpressionInfo.Expression as MemberExpression).Member.Name;
var QuotedColumnName = GetQuotedColumnName(tableDef, columnName);
if (m.Member.Name == "Year")
{
return new PartialSqlString(string.Format("DATEPART(yyyy,{0})", QuotedColumnName));
}
if (m.Member.Name == "Month")
return new PartialSqlString(string.Format("DATEPART(mm,{0})", QuotedColumnName));
}
if (ExpressionInfo.Member.Name == nameof(Nullable<bool>.HasValue))
{
var doesNotEqualNull = Expression.NotEqual(ExpressionInfo.Expression, Expression.Constant(null));
return Visit(doesNotEqualNull); // Nullable<T>.HasValue is equivalent to "!= null"
}
}
else
{
var modelType = ExpressionInfo.Expression.Type;
var tableDef = modelType.GetModelDefinition();
var columnName = ExpressionInfo.Member.Name;
var QuotedColumnName = GetQuotedColumnName(tableDef, columnName);
if (m.Member.Name == "Year")
return new PartialSqlString(string.Format("DATEPART(yyyy,{0})", QuotedColumnName));
if (m.Member.Name == "Month")
return new PartialSqlString(string.Format("DATEPART(mm,{0})", QuotedColumnName));
}
}
if (m.Expression.NodeType == ExpressionType.Parameter || m.Expression.NodeType == ExpressionType.Convert)
{
var propertyInfo = (PropertyInfo)m.Member;
var modelType = m.Expression.Type;
if (m.Expression.NodeType == ExpressionType.Convert)
{
var unaryExpr = m.Expression as UnaryExpression;
if (unaryExpr != null)
{
modelType = unaryExpr.Operand.Type;
}
}
var tableDef = modelType.GetModelDefinition();
if (propertyInfo.PropertyType.IsEnum)
return new EnumMemberAccess(
GetQuotedColumnName(tableDef, m.Member.Name), propertyInfo.PropertyType);
return new PartialSqlString(GetQuotedColumnName(tableDef, m.Member.Name));
}
}
var member = Expression.Convert(m, typeof(object));
var lambda = Expression.Lambda<Func<object>>(member);
var getter = lambda.Compile();
return getter();
}
modify VisitLambda method :
protected virtual object VisitLambda(LambdaExpression lambda)
{
if (lambda.Body.NodeType == ExpressionType.MemberAccess && sep == " ")
{
MemberExpression m = lambda.Body as MemberExpression;
if (m.Expression != null)
{
string r = VisitMemberAccess(m).ToString();
if (m.Member.DeclaringType.IsNullableType())
return r;
return string.Format("{0}={1}", r, GetQuotedTrueValue());
}
}
return Visit(lambda.Body);
}
This is nature of the Linq. In order to achieve what you need, you will need to use two where closes:
dbConn.Where<Product>(p => p.IsActive.HasValue).Where(p=>p.Value==true);
Looking at the Scala 2.10.0's implementation of LinearSeqOptimized#find in LinearSeqOptimized.scala, why is it necessary to call var these = this?
Why couldn't this simply be used?
override /*IterableLike*/
def find(p: A => Boolean): Option[A] = {
var these = this
while (!these.isEmpty) {
if (p(these.head)) return Some(these.head)
these = these.tail
}
None
}
Because you would have to have the same condition and operation out of the loop for this and then start using these.
It's much simpler to just put everyone in the same basket and do it all in the loop itself. Example:
def find(p: A => Boolean): Option[A] = {
if (!this.isEmpty && p(this.head)) {
return Some(this.head)
}
var these = this.tail
while (!these.isEmpty) {
if (p(these.head)) return Some(these.head)
these = these.tail
}
None
}
Not very smart, as you can see.
You could also easily implement this as a #tailrec operation:
#tailrec final def find[A](p : A => Boolean) : Option[A] = {
if ( this.isEmpty ) {
None
} else {
if ( p(this.head) ) {
Some(this.head)
} else {
this.tail.find(p)
}
}
}
And it isn't done like this in Scala because tailrec calls have to be final or private.