Is there a problem with calling an expression inside another expression ? Cause when I do:
create expression int js:hexToBin(hex) [
var bin = '';
for (var i = 0; i <= hex.length - 1; i += 1) {
bin += ('0000' + parseInt(hex.substr(i, 1), 16).toString(2)).slice(-4);
};
parseInt(bin, 2);
];
create expression int js:getTemperature(hex) [
hexToBin(hex.substring(4, 6));
];
I got an error \"hexToBin\" is not defined. (getTemperature#2). But when I put all of the code in getTemperature it works properly.
As already said in the expression you are in JavaScript and it has no idea of esper.
But an expression does not need to contain a single function. It is just some entry to a script so you can define multiple JavaScript functions within a single expression if you want to structure the code.
The JavaScript code is not aware of the EPL expressions. It would be interesting to research whether Rhino could be told of the EPL expressions.
Related
Use case: I am converting data from a very old program of mine to a database friendly format. There are parts where I have to do multiple passes over the old data, because in particular the keys have to first exist before I can reference them in relationships. So I thought why not put the incomplete parts in a vector of references during the first pass and return it from the working function, so I can easily use that vector to make the second pass over whatever is still incomplete. I like to avoid pointers when possible so I looked into std::reference_wrapper<T> which seemes like exactly what I need .. except I don't understand it's behavior at all.
I have both vector<OldData> old_data and vector<NewData> new_data as member of my conversion class. The converting member function essentially does:
//...
vector<reference_wrapper<NewData>> incomplete;
for(const auto& old_elem : old_data) {
auto& new_ref = *new_data.insert(new_data.end(), convert(old_elem));
if(is_incomplete(new_ref)) incomplete.push_back(ref(new_ref));
}
return incomplete;
However, incomplete is already broken immediately after the for loop. The program compiles, but crashes and produces gibberish. Now I don't know if I placed ref correctly, but this is only one of many tries where I tried to put it somewhere else, use push_back or emplace_back instead, etc. ..
Something seems to be going out of scope, but what? both new_data and old_data are class members, incomplete also lives outside the loop, and according to the documentation, reference_wrapper is copyable.
Here's a simplified MWE that compiles, crashes, and produces gibberish:
// includes ..
using namespace std;
int main() {
int N = 2; // works correctly for N = 1 without any other changes ... ???
vector<string> strs;
vector<reference_wrapper<string>> refs;
for(int i = 0; i < N; ++i) {
string& sref = ref(strs.emplace_back("a"));
refs.push_back(sref);
}
for (const auto& r : refs) cout << r.get(); // crash & gibberish
}
This is g++ 10.2.0 with -std=c++17 if it means anything. Now I will probably just use pointers and be done, but I would like to understand what is going on here, documentation / search does not seem to help..
The problem here is that you are using vector data structure which might re-allocate memory for the entire vector any time that you add an element, so all previous references on that vector most probably get invalidated, you can resolve your problem by using list instead of vector.
I encountered an error in a script I was debugging because somebody had created a variable with a name matching a built-in function, rendering the function inaccessible. I got strange errors when I tried to use the function, like:
incorrect arguments for (-)
incorrect arguments for (by)
incorrect arguments for ([)
incorrect arguments for (=)
Example code:
int length
// ...
// ...
string substr
string str = "big long string with lots of text"
substr = str[0:length(str)-2]
Is there a way to access the original length() function in this situation? I was actually just trying to add debug output to the existing script, not trying to modify the script, when I encountered this error.
For now I have just renamed the variable.
Well, in the case that you had no chance to modify the code, e.g. because it is encrypted you could do sth like
int length_original (string s) { return length s }
<<here is the code of your function>>
int length (string s) {return length_original s }
If I have the following input
test = 3; //first
test = test + 3; //second
parsed with a grammar that looks like this (for example)
Declaration:
name=ID "=" DeclarationContent
;
DeclarationContent:
number=INT ("+" DeclarationContent)?
| reference=[Declaration] ("+" DeclarationContent)?
;
to which declaration does the reference refer (looking at the second declaration in my example)? Or in other words does the reference "test" (second Declaration) refer to the first Declaration ("test = 3;") or directly to itself ("test = test+ 3") and would therefor be a cycle in hierarchy.
Greeting Krzmbrzl
Xtext will always link a cross reference [Declaration] to the first elemenent which is identified by the given ID. In your example hello + 3, the cross reference behind hello will resolved to the declaration hello in line 1. But if you have more then one element with the same (qualified) name within the same scope (container of visibility) Xtext will throw an Exception. You should
implement your own ScopeProvider (Use the generated stub in your.dsl.scoping.YourDslScopeProvider) to resolve this problem or
Use the composed check to automatically validate names.
fragment = validation.JavaValidatorFragment auto-inject {
composedCheck = "org.eclipse.xtext.validation.NamesAreUniqueValidator"
}
Here is the function
calc.lua:
function foo(n)
return n*2
end
Here is my LuaJavaCall
L.getGlobal("foo");
L.pushJavaObject(8);
int retCode=L.pcall(1,1,0); // nResults)//L.pcall(1, 1,-2);
String errstr = L.toString(-1); // Attempt to perform arithmetic on local variable 'n'
Update: as indicated below I needed to use L.pushNumber(8.0) instead of L.pushJavaObject()
Try using L.pushNumber instead of L.pushJavaObject like this:
L.getGlobal("foo");
L.pushNumber(8.0);
int retCode = L.pcall(1,1,0);
String errstr = L.toString(-1);
Lua probably sees JavaObject as a type of 'userdata' in which case there are no predefined operations for it; Lua won't know what to do with a JavaObject * 2 since you didn't define how to handle it.
OTOH, Lua does know how to handle a number since that's a builtin primitive type. For the code snippet you presented, pushing a number would be the least painful way to get it working instead of writing extra code that tells Lua how to work with numbers wrapped inside a JavaObject.
I am trying to use System.Data.Sqlite with F#. In C#, I have code like
using (DbTransaction dbTrans = con.BeginTransaction()) {
using (SQLiteCommand cmd = con.CreateCommand()) {
//blahblah
}
dbTrans.Commit();
}
But in F#, when I use the similiar two using above I got error of the type bool is not compatible with the type IDisposable...
EDIT I am really sorry for my question. use would work in F# case. I just dont know how to close/delete my quesetions.
To add some details - if you need to explicitly mark the scope where command is valid (to get exactly the same behavior as in your C# example, where cmd id disposed of before calling Commit) you can write:
use dbTrans = con.BeginTransaction()
( use cmd = con.CreateCommand()
cmd.BlahBlahBlah() )
dbTrans.Commit()
The scope is just a part of expression where the symbol is defined, so you can make it explicit using parentheses.
using is just an F# function that you could use before special syntax using use was added. Just FYI, the syntax looks like this:
using (con.BeginTransaction()) (fun dbTrans ->
using (con.CreateCommand()) (fun cmd ->
cmd.BlahBlahBlah() )
dbTrans.Commit() )
Writing the code using use is definitely a better idea (but you can define your functions like using to encapsulate more interesting behavior - e.g. transaction).
in f# it's
use dbTrans = new con.BeginTransaction ()
and
use cmd = con.CreateCommand()
these will dispose when your function ends