thanks for taking the time to read my problem.
I have this warning in my console : The function 'ta.ema' should be called on each calculation for consistency. It is recommended to extract the call from this scope.
So you can see the image of the script I did, I tried different alternative and still have the same warning, also the label.new still doesn't appearenter image description here on my chart.
Thanks for your help !
try to use ta.ema before the beginning of the if loop and store its value in a variable, then use that variable everywhere
you calculate several times the same calculus
and that's not good programming
as said above : "put the ta.ema in a variable" on a level-1 instruction
then use the variable everywhere
so it's less time consuming.
Related
enter image description here
it show warning
I was suppose to arrange the numbers, In order irrespective of the values, but to move 0 come at last.
To learn what you are doing wrong you need to read a book in C. Basic one.
I can point some errors and good practices.
comparison is done by ==. so you should use if(i==0)
After the second for loop you would want to change the value of i to 0. i=0.
the two for loops should be run upto the point when i<n and j<n.
That if(a[i]==0) comparison is not needed.
You don't need the while loop here.
You can print all of them after the for-for looping.
Global variables are used but you should have a good reason to use that.
Index variables are better if declared and defined locally.
what you are trying to do is known as Bubble sort.
Even after understanding all this and following this you get error try to run it through debugger, try small value of n.
Then if you can't, then ask here.
I've searched extensively, and thought I wouldn't be the only one having this problem, but it seems to look like I am.
I am solving an ode via ode15s (my problem can be stiff) and I use the 'Events' option to find my point of interest.
The problem is: the equation that I use in 'value' is depending (among other things) on the specific time (so value = f(t,y,y'), and I cannot find a way of passing the current time to this function, only the y vector is available.
Anyone has any ideas?
Thanks in advance and all the enjoy the rest of your holidays!
Sorry, made a really stupid error (used , instead of ;)...
You can just use the t argument as long as you set it in your #odefunction(t,y) as well as your #events(t,y).
What does a period with a name before a function mean when calling it in Arduino code (C/C++)?
For example, I am using an OLED display library and one function is called like this:
display.setTextSize(1);
I know what this function does, but what does the syntax mean where there is some variable "display" or something before it?
In other words, why is a function called this way versus a normal call with just the function name and input?
"display" is an instance of an object, or a reference to some global/system variable. The "setTextSize" method is a member of that object. The end result means that you are setting the text size of, or on, "display".
This lets you do things more concisely by being able to say display.setTextSize(1), foo.setTextSize(1) and bar.setTextSize(1) without having to specify unique functions for each different item on which you are setting the text size.
Within setTextSize you will probably see "this". "this" in only this one instance means "display". If you used bar.setTextSize(1), "this" would mean "bar" and so on.
I could be incredibly wrong, but I think its got to do with structures. In the arduino environment there's a few different functions that revolve around using serial communication. They have it set up as a library that gets called on whenever you use Serial.something();
The something could be any of the functions that is part of serial, like Serial.read();
EDIT forgot to put a source in. http://arduino.cc/en/Reference/Serial
Apologies if I'm way off, still new at this, and also can't figure out how to just make a comment.
Sometimes I accidentally declare variables that have the name of a function.
Here is a constructed example:
max(4:5) % 5
max(1:10)=10*ones(10,1); % oops, should be == instead of =
max(4:5) % [10 10]
At the moment I always find this out the hard way and it especially happens with function names that I don't use frequently.
Is there any way to let matlab give a warning about this? It would be ideal to see this on the right hand side of the screen with the other warnings, but I am open to other suggestions.
Since Matlab allows you to overload built-in functionality, you will not receive any warnings when using existing names.
There are, however, a few tricks to minimize the risk of overloading existing functions:
Use explicitFunctionNames. It is much less likely that there is a function maxIndex instead of max.
Use the "Tab"-key often. Matlab will auto-complete functions on the path (as well as variables that you've declared previously). Thus, if the variable auto-completes, it already exists. In case you don't remember whether it's also a function, hit "F1" to see whether there exists a help page for it.
Use functions rather than scripts, so that "mis-"assigned variables in the workspace won't mess up your code.
I'm pretty sure mlint can also check for that.
Generally I would wrap code into functions as much as possible. That way the range of such an override is limited to the scope of the function - so no lasting problems, besides the accidental assumption of course.
When in doubt, check:
exist max
ans =
5
Looking at help exist, you can see that "max" is a function, and shouldn't be assigned as a variable.
>> help exist
exist Check if variables or functions are defined.
exist('A') returns:
0 if A does not exist
1 if A is a variable in the workspace
2 if A is an M-file on MATLAB's search path. It also returns 2 when
A is the full pathname to a file or when A is the name of an
ordinary file on MATLAB's search path
3 if A is a MEX-file on MATLAB's search path
4 if A is a MDL-file on MATLAB's search path
5 if A is a built-in MATLAB function
6 if A is a P-file on MATLAB's search path
7 if A is a directory
8 if A is a class (exist returns 0 for Java classes if you
start MATLAB with the -nojvm option.)
I sometimes use temporary variables to shorten the identifiers:
private function doSomething() {
$db = $this->currentDatabase;
$db->callMethod1();
$db->callMethod2();
$db->callMethod3();
$db->...
}
Although this is a PHP example, I'm asking in general:
Is this bad practice? Are there any drawbacks?
This example is perfectly fine, since you are using it in functions/methods.
The variable will be unset right after the method/function ends - so there's not much of a memory leak or what.
Also by doing this, you "sort of" implemented DRY - don't repeat yourself.
Why write so many $this->currentDatabase when you can write $db. And what if you have to change $this->currentDatabase to some other values?
Actually, you're not trying to avoid typing (otherwise, you'd use a completion mechanism in your editor), but you're just making your function more readable (by using "abbreviations") which is a good thing.
Drawbacks will show up when you start doing this to avoid typing (and sacrifice readability)
It depends what is the contract on $this->currentDatabase. Can it change at any time, after any method call? If it changes, are you supposed to keep on using the object you did when you made your first db call, or are you supposed to always us the current value? This dictates if you must always use $this->currentDatabase, or if you must always store it in a variable before using.
So, strictly speaking, this is not a style question at all.
But, assuming the member is never changed during function calls such as this, it makes no difference. I'd say storing it in a variable is slightly better, as it is easier to read and avoids a member access on an object at every operation. The compiler may optimize it away if it's good, but in many languages such optimizations are very difficult - and accessing a local variable is almost invariably faster than accessing a member of an object.
In general :
Both $db as $this->currentDatabase point to exactly the same object.
The little space allocated for $db is freed (or elligeable for garbage collection) when the function ends
so I'd say : no, it's not bad practice.
I seem to remember that Steve McConnell recommends against using temporary variables in "Code Complete". At the risk of committing heresy, I have to disagree. I prefer the additional readability introduced. I also find myself adding them to aid single-step debugging, then seeing no reason to remove them.
I don't think there is a performance penalty if you use the original variable instead of skipping the first dereference ($this->currentDatabase).
However, as readability is much improved using the abbreviation, go for it!
Of course it also will depend on your team's coding conventions.
If you do this carefully it is absolutely fine. As long as you only use a few of this variables in a small amount of code and inside of small functions I think this is ok.
If you have a lot of this variables and they are badly named like i,j,l and f in the same function the understandability of your code will suffer. If this is the case I would rather type a little bit more then have not understandable code. This is one reason a good IDE has automatic code completion.
No, I think, this is ok. Often performance if not as critical as clean readable code.
Also, you are trading memory a small allocation hit on the stack for faster method calls by avoiding extra dereferencing.
A getter will solve your problem:
private function doSomething() {
getDB()->callMethod1();
getDB()->callMethod2();
getDB()->callMethod3();
}
by clean code N.