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.
Related
I have a large contract and I am in the process of splitting it out into two. The goal is to have the functions that are common (and will be used by many other contracts) to be separated out for efficiency.
One of these functions compares items in arrays "ownedSymbols" and "targetAssets". It produces a list "sellSymbols" if any item in "ownedSymbols" is not in "targetAssets".
The below code works fine while "sellSymbols" is stored as a string. As this function will become common, I need it to run in memory so the results aren't confused by calls from different contracts.
pragma solidity >0.8.0;
contract compareArrays {
string[] public ownedSymbols = ["A","B","C"];
string[] public targetAssets = ["A","B"];
string[] sellSymbols;
event sellListEvent(string[]);
function sellList(string[] memory _ownedSymbols, string[] memory _targetAssetsList) internal {
sellSymbols = _ownedSymbols;
for (uint256 i = 0; i < _targetAssetsList.length; i++) {
for (uint256 x = 0; x < sellSymbols.length; x++) {
if (
keccak256(abi.encodePacked((sellSymbols[x]))) ==
keccak256(abi.encodePacked((_targetAssetsList[i])))
) {
if (x < sellSymbols.length) {
sellSymbols[x] = sellSymbols[sellSymbols.length - 1];
sellSymbols.pop();
} else {
delete sellSymbols;
}
}
}
}
emit sellListEvent(sellSymbols);
}
function runSellList() public {
sellList(ownedSymbols,targetAssets);
}
}
Ideally the function would run with "string[] memory sellSymbols", however this kicks back an error.
pragma solidity >0.8.0;
contract compareArrays {
string[] public ownedSymbols = ["A","B","C"];
string[] public targetAssets = ["A","B"];
event sellListEvent(string[]);
function sellList(string[] memory _ownedSymbols, string[] memory _targetAssetsList) internal {
string[] memory sellSymbols = _ownedSymbols;
for (uint256 i = 0; i < _targetAssetsList.length; i++) {
for (uint256 x = 0; x < sellSymbols.length; x++) {
if (
keccak256(abi.encodePacked((sellSymbols[x]))) ==
keccak256(abi.encodePacked((_targetAssetsList[i])))
) {
if (x < sellSymbols.length) {
sellSymbols[x] = sellSymbols[sellSymbols.length - 1];
sellSymbols.pop();
} else {
delete sellSymbols;
}
}
}
}
emit sellListEvent(sellSymbols);
}
function runSellList() public {
sellList(ownedSymbols,targetAssets);
}
}
The error:
TypeError: Member "pop" is not available in string memory[] memory outside of storage.
--> contracts/sellSymbols.sol:20:25:
|
20 | sellSymbols.pop();
| ^^^^^^^^^^^^^^^
Two questions from me:
Is there a way to do this in memory so that the function can be common (i.e. used by multiple contracts at the same time)?
Is there a better way? The below is expensive to run, but it is the only way I have been able to achieve it.
One final comment - I know this would be much easier/cheaper to run off chain. That is not something I am willing to consider as I want this project to be decentralized.
If you want to keep the existing system, the best solution is described here: https://stackoverflow.com/a/49054593/11628256
if (x < sellSymbols.length) {
sellSymbols[x] = sellSymbols[sellSymbols.length - 1];
delete sellSymbols[myArray.length - 1];
sellSymbols.length--;
} else {
delete sellSymbols;
}
If all you care about is the presence or absence of a particular asset (and not enumerating through them), what you're going to want to do to really reduce gas costs is something called "lazy evaluation." Lazy evaluation is when instead of computing all results at once (like increasing all balances by 50% by iterating over an array), you modify the getters so that their return value reflects the operation (such as multiplying an internal variable by 50% and multiplying the original result of getBalance by that variable).
So, if this is the case, what you want to do is use the following function instead:
function except(string _item, mapping(string => bool) _ownedSymbols, mapping(string => bool) _targetAssets) internal returns (bool) {
return _ownedSymbols[_item] && !_targetAssets[_item];
}
<pet peeve>
Finally, I know you say you want this to be decentralized, but I really do feel the urge to say this. If this is a system that doesn't need to be decentralized, don't decentralize it! Decentralization is great for projects that other people rely on - for example, DNS or any sort of token.
From your variable names, it seems that this is probably some sort of system similar to a trading bot. Therefore, the incentive is on you to keep it running, as you are the one that gets the benefits. None of the problems that decentralization solves (censorship, conflict of interest, etc...) apply to your program, as the person running it is incentivized to keep it running and keep a copy of the program. It's cheaper for the user running it to not have security they don't need. You don't need a bank-grade vault to store a $1 bill!
</pet peeve>
Every Ruby object is of type VALUE in C. How do I print it in a readable way?
Any other tips concerning debugging of Ruby C extensions are welcome.
You can call p on Ruby objects with the C function rb_p. For example:
VALUE empty_array = rb_ary_new();
rb_p(empty_array); // prints out "[]"
Here's what I came up with:
static void d(VALUE v) {
ID sym_puts = rb_intern("puts");
ID sym_inspect = rb_intern("inspect");
rb_funcall(rb_mKernel, sym_puts, 1,
rb_funcall(v, sym_inspect, 0));
}
Having it in a C file, you can output VALUEs like so:
VALUE v;
d(v);
I've borrowed the idea from this article.
I've found an interesting way using Natvis files in Visual Studio.
I have created C++ wrapper objects over the Ruby C API - this gives me a little bit more type safety and the syntax becomes more similar to writing actual Ruby.
I won't be posting the whole code - too long for that, I plan on open sourcing it eventually.
But the gist of it is:
class Object
{
public:
Object(VALUE value) : value_(value)
{
assert(NIL_P(value_) || kind_of(rb_cObject));
}
operator VALUE() const
{
return value_;
}
// [More code] ...
}
Then lets take the String class for example:
class String : public Object
{
public:
String() : Object(GetVALUE("")) {}
String(VALUE value) : Object(value)
{
CheckTypeOfOrNil(value_, String::klass());
}
String(std::string value) : Object( GetVALUE(value.c_str()) ) {}
String(const char* value) : Object( GetVALUE(value) ) {}
operator std::string()
{
return StringValueCStr(value_);
}
operator std::string() const
{
return operator std::string();
}
static VALUE klass()
{
return rb_cString;
}
// String.empty?
bool empty()
{
return length() == 0;
}
size_t length() const
{
return static_cast<size_t>(RSTRING_LEN(value_));
}
size_t size() const
{
return length();
};
};
So - my wrappers make sure to check that the VALUE they wrap is of expected type or Nil.
I then wrote some natvis files for Visual Studio which will provide some real time debug information for my wrapper objects as I step through the code:
<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
<Type Name="SUbD::ruby::String">
<DisplayString Condition="value_ == RUBY_Qnil">Ruby String: Nil</DisplayString>
<DisplayString Condition="value_ != RUBY_Qnil">Ruby String: {((struct RString*)value_)->as.heap.ptr,s}</DisplayString>
<StringView Condition="value_ != RUBY_Qnil">((struct RString*)value_)->as.heap.ptr,s</StringView>
<Expand>
<Item Name="[VALUE]">value_</Item>
<Item Name="[size]" Condition="value_ != RUBY_Qnil">((struct RString*)value_)->as.heap.len</Item>
<Item Name="[string]" Condition="value_ != RUBY_Qnil">((struct RString*)value_)->as.heap.ptr</Item>
<Item Name="[capacity]" Condition="value_ != RUBY_Qnil">((struct RString*)value_)->as.heap.aux.capa</Item>
</Expand>
</Type>
</AutoVisualizer>
Note that this is all hard-coded to the exact internal structure of Ruby 2.0. This will not work in Ruby 1.8 or 1.9 - haven't tried with 2.1 or 2.2 yet. Also, there might be mutations of how the String can be stored which I haven't added yet. (Short strings can be stored as immediate values.)
(In fact - the natvis posted above only works for 32bit - not 64bit at the moment.)
But once that is set up I can step through code and inspect the Ruby strings almost like they are std::string:
Getting it all to work isn't trivial. If you noticed in my natvis my RUBY_Qnil references - they would not work unless I added this piece of debug code to my project:
// Required in order to make them available to natvis files in Visual Studio.
#ifdef _DEBUG
const auto DEBUG_RUBY_Qnil = RUBY_Qnil;
const auto DEBUG_RUBY_FIXNUM_FLAG = RUBY_FIXNUM_FLAG;
const auto DEBUG_RUBY_T_MASK = RUBY_T_MASK;
const auto DEBUG_RUBY_T_FLOAT = RUBY_T_FLOAT;
const auto DEBUG_RARRAY_EMBED_FLAG = RARRAY_EMBED_FLAG;
const auto DEBUG_RARRAY_EMBED_LEN_SHIFT = RARRAY_EMBED_LEN_SHIFT;
const auto DEBUG_RARRAY_EMBED_LEN_MASK = RARRAY_EMBED_LEN_MASK;
#endif
You cannot use macros in natvis definitions unfortunately, so that's why I had to manually expand many of them into the natvis file by inspecting the Ruby source itself. (The Ruby Cross Reference is of great help here: http://rxr.whitequark.org/mri/ident?v=2.0.0-p247)
It's still WIP, but it's already saved me a ton of headaches. Eventually I want to extract the debug setup on GitHub: https://github.com/thomthom (Keep an eye on that account if you are interested.)
I'm trying to make a bomb catching game (I'm actually using the code from the AS3 Classroom in a Book on arrays). As soon as I changed the word fruit to bomb in the code I got error 1007. With the exception of changing basket_mc to eod_mc and fruit to bomb (I used command-F and replaced with case sensitive on) I haven't changed much. It worked with eod_mc, but doesn't with bomb.
var bombArray:Array = new Array(bomb);
var bombsOnstage:Array = new Array();
var bombsCollected:int = 0;
var bombsLost:int = 0;
for (var i:int = 0; i<20; i++) {
var pickBomb = bombArray[int(Math.random() * bombArray.length)];
var bomb:MovieClip = new pickBomb();
addChild(bomb);
bomb.x = Math.random() * stage.stageWidth-bomb.width;// bomb.width is subtracted from the random x position to elimate the slight possibility that a clip will be placed offstage on the right.
bomb.y = Math.random() * -500;
bomb.speed = Math.random() * 15 + 5;
bombsOnstage.push(bomb);
}
eod_mc.addEventListener(MouseEvent.MOUSE_DOWN, dragEod);
stage.addEventListener(MouseEvent.MOUSE_UP, dragStop);
function dragEod(e:Event):void {
eod_mc.startDrag();
}
function dragStop(e:Event):void {
eod_mc.stopDrag();
}
stage.addEventListener(Event.ENTER_FRAME, catchBomb);
function catchBomb(e:Event):void {
for (var i:int = bombsOnstage.length-1; i > -1; i--) {
var currentBomb:MovieClip = bombsOnstage[i];
currentBomb.y += currentBomb.speed;
if (currentBomb.y > stage.stageHeight - currentBomb.height) {
currentBomb.y = 0 - currentBomb.height;
bombsLost++;
field2_txt.text = "Total Bombs Detonated: " + bombsLost;
}
if (currentBomb.hitTestObject(eod_mc)) {
bombsCollected++;
removeChild(currentBomb);
bombsOnstage.splice(i,1);
field1_txt.text = "Total Bombs Caught: " + bombsCollected;
if (bombsCollected >= 20) {
eod_mc.gotoAndStop(20);
} else if (bombsCollected > 15) {
eod_mc.gotoAndStop(15);
} else if (bombsCollected>10) {
eod_mc.gotoAndStop(10);
} else if (bombsCollected>5) {
eod_mc.gotoAndStop(5);
}
}
}
if (bombsOnstage.length <= 0) {
field1_txt.text = "You Win! You have defused the bombs.";
field2_txt.text = "";
stage.removeEventListener(Event.ENTER_FRAME, catchBomb);
}
if (bombsLost >= 20) {
field1_txt.text = "Sorry you lose. You have lost your foot!";
field2_txt.text = "";
stage.removeEventListener(Event.ENTER_FRAME, catchBomb);
for (var j:int = bombsOnstage.length-1; j > -1; j--) {
currentBomb = bombsOnstage[j];
removeChild(currentBomb);
bombsOnstage.splice(j,1);
}
}
}
Maybe to avoid making your programming life more twisted than it is now...
There are objects and classes in programming, a class is a description of a set of objects, say "table" (or, as it's better to differ in names for classes and variables, "Table", first letter capitalized) is a name of a class. An instance or an object is a structure that belongs to one or more classes, with Object being the topmost, as everything in programming is either an object or a "simple variable", that is, a number, a true/false, a string of characters (these are object types in AS3 too, though, Number, Boolean, String, but these generally not need to be instantiated via new) or probably some other simple type I don't remember right now.
Classes have properties and methods. A property is something that can be requested off any object of the class, say "height" for tables. Properties can be of any type, including nested objects, depending on what your base class is. Say stage in AS3 is a property of any DisplayObject which is used to get the only Stage object there is at runtime[1]. Methods are what any object of a class can be told to do. Say, bombs fall, explode, MovieClips can be told to stop(), etc. You write class code keeping in mind that all of the objects of this class will have to behave exactly like you've written, but since they can differ in properties, you can give them conditional behavior. For example, if a bomb has already exploded, it cannot blow up once more.
A variable, whether a property or a standalone var (if you declare one in a function) is a reference to an object of a given type. Say var i:int refers to some kind of an integer. Simple type vars are containers instead, that is, i=2; will place a 2 in the referred integer, and i=j; will copy the value from j into i, while var theStage:Stage=this.stage will instead create a reference to an existing object, and if that object will change, the reference will give you the changed object instead of its previous state. An array is a collection of variables, reachable by indexes, in AS3 they don't have to be of one type, and a Vector is a typed array.
Next, the lifetime of objects. An object only lives while there's an active reference to it, whether in a property of another alive object, or in a visible variable, or in an event listener (AS3 specific). An object is created via new ClassName(<parameters>), lives while you can reach it somehow, and is destroyed once you have no active links to it and Flash player decides to run garbage collector. Prior to this programmers had to deallocate objects themselves, a rudiment can be seen at BitmapData.dispose(). So, in order to avoid Flash player to run out of free memory, take full control over creation and destruction of links. You don't need to care for simple vars, they are being cared for by Flash player.
A lot of basic functions for interactions has already been implemented in AS3, look for them and examples of how they work in Adobe's manual, navigate through packages in the lower left, most of the interactive stuff is in flash.display package, refer to other packages as necessary.
Hope this will bring you some insight into programming basics.
[1]: There is one stage unless you're doing a load of an SWF, then there could be more, one Stage per one SWF.
I know there are quite similar questions here, but I haven't found the proper details. What would be helpful is definitely an explanation of the problems, and perhaps a base example, that anyone who searches later may be able to apply. (Not asking that you write it for me, I just find the examples helpful) I don't want to upset anyone and am kind of worried to post in a forum...
I am wondering alternatives to creating a screen based off tiles created from an array. I have been having an issue myself trying to access the movieclips that have been placed on screen, and trying to trace to find a way to reference them hasn't been working.
Anyway, take something basic like an array, and connecting it to movieclips, then how to access the movieclip itself once done. So I have been working on this, and used many different online resources, so I'm sure a lot of this is going to look familiar, just in a much messier way.
This takes the array to make the movieclips appear (Im sure at least one part in here is unnecessary, and I'm thinking I'm doing something wrong here that makes it not work out later) So this works, but feels pretty bulky.
Both are from the same main class file.
function makeWorld (anyMap, tileW, tileH) {
var worldWidth = anyMap[0].length;
var worldHeight = anyMap.length;
var MAP = this.addChild(new mapHolder());
function tiler(MAP, i, j, tileW, tileH, tile)
{
MAP.addChild(tile);
tile.x = (j * tileW);
tile.y = (i * tileH);
}
for (var i = 0; i < worldWidth; ++i) {
for (var j = 0; j < worldHeight; ++j) {
var curTile:int = anyMap[i][j];
if (curTile == 101) {
var tile1 = new tileGround();
tiler (MAP, i, j, tileW, tileH, tile1);
...
else {
var tile3 = new empty();
tiler (MAP, i, j, tileW, tileH, tile3);
}
}}}
Then there is attempting to reference it, where I'm having the issue. I don't know what to call this.MAP.tileGround by, and I have tried many things. I've read it's not such a good idea to reference by name when not very advanced so I wanted to avoid that sort of thing too.
addEventListener (Event.ENTER_FRAME, hits);
function hits (event:Event) {
var tileCatchG:MovieClip = this.MAP.tileGround;
if(tileCatchG.hitTestPoint(this.MAP.Char.x + leftBumpPoint.x, this.MAP.Char.y + leftBumpPoint.y, true)){
leftBumping = true;
} else {
leftBumping = false;
}
...
}
Thank you!
In looking over what you're doing a second time it would appear that you should have a reference to the 2-indexed array that represents the map.
You can create a regular (single indexed) Array at the top of the file like
public var tileArray:Array = [];
Then where you create them push them into the array
var tile1 = new tileGround();
tileArray.push(tile1);
then to reference them all you can just run a simple loop
for each(var tile:MovieClip in tileArray)
{
//Do stuff
if(tile instanceof tileGround)
{
//Do stuff specific to tileGround
}
}
I have an array which is filled with platforms that are supposed to move.
var MovingPlatformArray:Array = new Array();
for (var c:int = numChildren - 1; c >= 0; c--){
var child3:DisplayObject = getChildAt(c);
if (child3.name == "movingplatform"){
MovingPlatformArray.push(child3);
}
}
this.addEventListener(Event.ENTER_FRAME,ctrl_birdie);
function ctrl_birdie(e:Event):void{
for(var c in MovingPlatformArray){
MovingPlatform[c].y += speed;
if(MovingPlatformArray[c].hitTestPoint(birdie.x,birdie.y,true)){
birdtelleryvertrager=0;
birdtellery = 0;
birdie.y-=14;
}
if(movingplatform.y <= 25){
speed = 2;
}
if(movingplatform.y >= 350){
speed = -2;
}
}
Right now I have 2 moving platforms in this array. But only one moves up and down. But they both register a touch with the birdie. Am I doing something wrong?
In your listener, you're only setting the position of one platform, which ever one "movingplatform" is a reference to. As all your stage instances of moving platforms are named "movingplatform", one lucky platform is getting referenced by name (the rest ignored), instead of what you intended, which is to use the references in your array and adjust each platform.
You probably meant for movingplatform to be a local variable in your event handler, declared something like this:
var movingplatform:DisplayObject = MovingPlatformArray[c] as DisplayObject;
I'd recommend using a for each loop in place of the for in, because I think it's a little cleaner, but this is a minor style thing:
for each (var platform:DisplayObject in MovingPlatformArray)
{
platform.y += speed;
... rest of your code ...
}
For the sake of clarity, I edited the loop variable to be platform instead of movingplatform, to avoid confusion of having a local variable shadow a stage instance (i.e. this.movingplatform). I wanted it to be clear that the stage instance name is not being used here, because the unintentional instance name reference in your code is the source of your problem in the first place.
As far as i'm concerned, you have two options. use a for each, as adam smith suggested or use a for-loop as it was intended to be used :)
for(var c:uint = 0; c < MovingPlatformArray.length; c++){...
and btw: should "MovingPlatform[c].y += speed;" not be "MovingPlatformArray[c].y += speed;"?
edit: looking at your code, i would also suggest you use MovingPlatformArray[c].hitTestObject(birdie) instead of MovingPlatformArray[c].hitTestPoint(birdie.x,birdie.y,true)
If I were you, I would bring the logic for the platform out, and store it in a class. (Ideally you would do this for the birdie object as well). I have created an example below. The movieclips on the stage should extend Platform rather than MovieClip so they invoke the methods at the bottom.
// Use vectors if you know all the items are going to be the same type
var platforms:Vector.<Platform> = new <Platform>[];
for (var c:int = numChildren - 1; c >= 0; c--){
var child:DisplayObject = getChildAt(c);
// You shouldn't check against names (as per the original post). Because
// names should be unique
if (child is Platform){
platforms.push(child);
// This could be random so each platform has a different range
// This means platform 1 could go from y 30 to y 400, platform 2
// could go from y 60 to y 200, etc
child.setRange(25, 400);
}
}
this.addEventListener(Event.ENTER_FRAME, gameLoop);
// Have an overall game loop
function gameLoop(e:Event):void {
// Loop over the platforms
platforms.forEach(function(item:Platform, i:int, a:Vector.<Platform>):void {
// Hit test function in the class means you only have to pass in one mc
// rather than the points and a boolean
if(item.hitTest(birdie)) {
birdtelleryvertrager=0;
birdtellery = 0;
birdie.y-=14;
}
// Removed the movement logic, this should be kept out of the game loop
// plus how much better does this read?
item.move();
});
}
Then in a class location somewhere, like in a folder game/activeObjects
// A class for the platform stored else where
package game.activeObjects
{
import flash.display.MovieClip;
/**
*
*/
public class Platform extends MovieClip {
private const SPEED:Number = 2;
private var _direction:int = 1;
private var _minimumHeight:Number = 25;
private var _maximumHeight:Number = 350;
public function Platform() {
}
public function setRange(minimumHeight:Number, maximumHeight:Number) {
_minimumHeight = minimumHeight;
_maximumHeight = maximumHeight;
}
public function move():void {
this.y += SPEED * _direction;
if(this.y <= _minimumHeight) {
_direction = 1;
} else if(this.y >= _maximumHeight) {
_direction = -1;
}
}
public function hitTest(mc:MovieClip):Boolean {
return hitTestPoint(mc.x,mc.y,true);
}
}
}