I'm currently having issues with Powershell. This is the line that errors:
while($minutes -le ($total_bots/$increment)) {
All of the above variables are numbers. I'm getting an error saying that it can't convert 60/5 - ($total_bots/$increment) - to a int32. I want the math operation completed, and then the condition evaluated. What am I missing?
Variables are declared like so:
[int]$minutes = 1
[int]$increment = 5
[int]$total_bots = 20
I didn't have the int there initially, but it still errors with it.
Was erroring below this after I changed them to [int]. Works now. Thanks
Related
Hello everyone I am new to scala and after seeing the do..while syntax which is the following:
do{
<action>
}while(condition)
I have been asked to perform this exercise which consists in predicting the output of a program containing the do..while loop.
var set = Set(1)
do {
set = set + (set.max + 1)
} while (set.sum < 32)
println(set.size)
After execution I get the following error:
end of statement expected but 'do' found
do {
I know that it is possible to convert this loop to while (which is even ideal), however I would like to know if the do..while loop still works in scala if yes, is it a syntax error (Because I searched on the net but I found the same syntax and no mention of this error)? if no, is there a version from which the loop is no longer supported?
You can still use do-while in Scala 2.13.10
https://scastie.scala-lang.org/DmytroMitin/JcGnZS3DRle3jXIUiwkb0A
In Scala 3 you can write do-while in while-do manner using Scala being expression-oriented (i.e. the last expression is what is returned from a block)
while ({
set = set + (set.max + 1)
set.sum < 32
}) {}
https://scastie.scala-lang.org/DmytroMitin/JcGnZS3DRle3jXIUiwkb0A/2
https://docs.scala-lang.org/scala3/reference/dropped-features/do-while.html
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I am new to PowerShell and there is a weird behavior I cannot explain. I call a function that returns a [System.Collections.ArrayList] but when I print my variable that receives the content of the array, if I have one value(for example: logXXX_20210222_075234355.txt), then I get 0 logXXX_20210222_075234355.txt. The value 0 gets added for some reason as if it has the index of the value.
If I have 4 values, it will look like this:
0 1 2 3 logXXX_20210222_075234315.txt logXXX_20210225_090407364.txt
logXXX_20210204_120318221.txt logXXX_20210129_122737751.txt
Can anyone help?
Here is a simple code that does that:
function returnAnArray{
$arrayToReturn =[System.Collections.ArrayList]::new()
$arrayToReturn.Add('logICM_20210222_075234315.txt')
return $arrayToReturn
}
$fileNames = returnAnArray
Write-Host $fileNames
0 logICM_20210222_075234315.txt
It's characteristic of the ArrayList class to output the index on .Add(...). However, PowerShell returns all output, which will cause it to intermingle the index numbers with the true or other intended output.
My favorite solution is to simply cast the the output from the .Add(...) method to [Void]:
function returnAnArray{
$arrayToReturn = [System.Collections.ArrayList]::new()
[Void]$arrayToReturn.Add('logICM_20210222_075234315.txt')
return $arrayToReturn
}
You can also use Out-Null for this purpose but in many cases it doesn't perform as well.
Another method is to assign it to $null like:
function returnAnArray{
$arrayToReturn = [System.Collections.ArrayList]::new()
$null = $arrayToReturn.Add('logICM_20210222_075234315.txt')
return $arrayToReturn
}
In some cases this can be marginally faster. However, I prefer the [Void] syntax and haven't observed whatever minor performance differential there may be.
Note: $null = ... works in all cases, while there are some cases where [Void] will not; See this answer (thanks again mklement0) for more information.
An aside, you can use casting to establish the list:
$arrayToReturn = [System.Collections.ArrayList]#()
Update Incorporating Important Comments from #mklement0:
return $arrayToReturn may not behave as intended. PowerShell's output behavior is to enumerate (stream) arrays down the pipeline. In such cases a 1 element array will end up returning a scalar. A multi-element array will return a typical object array [Object[]], not [Collection.ArrayList] as seems to be the intention.
The comma operator can be used to guarantee the return type by making the ArrayList the first element of another array. See this answer for more information.
Example without ,:
Function Return-ArrayList { [Collections.ArrayList]#(1,2,3,4,5,6) }
$ArrReturn = Return-ArrayList
$ArrReturn.gettype().FullName
Returns: System.Object[]
Example with ,:
Function Return-ArrayList { , [Collections.ArrayList]#(1,2,3,4,5,6) }
$ArrReturn = Return-ArrayList
$ArrReturn.gettype().FullName
Returns: System.Collections.ArrayList
Of course, this can also be handled by the calling code. Most commonly by wrapping the call in an array subexpression #(...). a call like: $filenames = #(returnAnArray) will force $filenames to be a typical object array ([Object[]]). Casting like $filenames = [Collections.ArrayList]#(returnArray) will make it an ArrayList.
For the latter approach, I always question if it's really needed. The typical use case for an ArrayList is to work around poor performance associated with using += to increment arrays. Often this can be accomplished by allowing PowerShell to return the array for you (see below). But, even if you're forced to use it inside the function, it doesn't mean you need it elsewhere in the code.
For Example:
$array = 1..10 | ForEach-Object{ $_ }
Is preferred over:
$array = [Collections.ArrayList]#()
1..10 | ForEach-Object{ [Void]$array.Add( $_ ) }
Persisting the ArrayList type beyond the function and through to the caller should be based on a persistent need. For example, if there's a need easily add/remove elements further along in the program.
Still More Information:
Notice the Return statement isn't needed either. This very much ties back to why you were getting extra output. Anything a function outputs is returned to the caller. Return isn't explicitly needed for this case. More commonly, Return can be used to exit a function at desired points...
A function like:
Function Demo-Return {
1
return
2
}
This will return 1 but not 2 because Return exited the function beforehand. However, if the function were:
Function Demo-Return
{
1
return 2
}
This returns 1, 2.
However, that's equivalent to Return 1,2 OR just 1,2 without Return
Update based on comments from #zett42:
You could avoid the ArrayList behavior altogether by using a different collection type. Most commonly a generic list, [Collections.Generic.List[object]]. Technically [ArrayList] is deprecated already making generic lists a better option. Furthermore, the .Add() method doesn't output anything, thus you do not need [Void] or any other nullification method. Generic lists are slightly faster than ArrayLists, and saving the nullification operation a further, albeit still small performance advantage.
ArrayList appears to store alternating indexes and values:
PS /home/alistair> $filenames[0]
0
PS /home/alistair> $filenames[1]
logICM_20210222_075234315.txt
I am upgrading my Matlab from 2013b to 2018b and have found out that MathWorks have made quite a few changes to the GUI's.
One problem I am having is getting the value of checkbox. The line below is the code I used to use but now it doesn't work.
if get(handles.check_perf_attr,'Value') == 1
The error message is,
Undefined operator '==' for input arguments of type 'cell'.
So I tried the line below to just get the value that is being returned and then apply some logic.
tValue = get(handles.check_perf_attr,'Value');
However tValue is 2 x 1 cell which in (1, 1) = 0 & (2, 1) = 1. I don't really understand this as surely a checkbox can only be one value true (1) or false (0)?
get returns a cell array with values when applied to an array of handles.
Thus, I think your problem is that handles.check_perf_attr contains two handles, not one.
"Dot notation is a new syntax to access object properties starting in R2014b."
so try
if handles.check_perf_attr.Value == 1
or
tValue = handles.check_perf_attr.Value;
Here is my 'for' loop:
let size:Int = 64
for var z = 0;z < size;++z{
}
I think the syntax is right, but the compiler always tells me:
is it bug or something?
ps: Xcode version6.1.1
From your screenshot, it looks like you're inserting code in the body of a class directly. You should move it to, e.g., the body of a method. Then it will compile fine.
I would still encourage you to insert spaces after ; and : for readability, however.
Here is my code:
function [im,sindx,end1]=alln(im,i,j,secret,sindx,end1)
slen=length(secret);
p=im(i,j);
neigh= [im(i-1,j) im(i+1,j) im(i,j-1) im(i,j+1) im(i-1,j-1) im(i+1,j-1) im(i-1,j+1) im(i+1,j+1)];
minpix = min (neigh)
maxpix = max (neigh)
if minpix < p < maxpix
lowlim = minpix+1;
highlim = maxpix-1;
range = highlim-lowlim+1;
nbits=floor(log2(abs(range)));
if sindx+nbits-1>slen
end1=1;
return
end
for k=1:nbits
bin(k)=secret(sindx+k-1);
end
b = bin2dec(bin);
newvalue1 = abs (minpix + b);
newvalue2 = abs (maxpix - b);
if abs(p-newvalue1)<= abs(p-newvalue2)
im(i,j) = newvalue1;
else
im(i,j) = newvalue2;
end
sindx=sindx+nbits;
end
end
My main program calls this function. When I run the program, I get the following error message:
??? Undefined function or variable "bin".
Error in ==> alln at 34
b = bin2dec(bin);
I know there are many experts for whom this is not a problem at all. I am new to MATLAB. Please guys, show me the way, which type of modification in the code can overcome this problem?
First of all, are there some lines missing from the file? Perhaps you've stripped some comments from the top? Because the error message says that
b = bin2dec(bin);
is line 34, but it's line 22 in the code you present.
OK, that aside...
The error message says that 'bin' isn't defined, but I see that it's being set on the line...
bin(k)=secret(sindx+k-1);
That suggests to me that THAT line isn't being run.
I see that that bin = ... line is inside of a 'for' loop, so I suspect that the for loop is run zero times, meaning that 'bin' never gets defined. What is nbits? Is it 1, or perhaps less than 1? THAT would prevent the loop from running at all.
Try removing the semicolon from the end of the
nbits=floor(log2(abs(range)));
line and run your code again.
Leaving off the semicolon will force the value of nbits to be printed in the Command Window. I bet you'll find that it's 1 or less. If that's the case, then start looking at HOW nbits is calculated, and I bet you'll find the problem.
At what input arguments to the function alln, are you getting the error?
Lets suppose that nbits is 0, then the following loop will not run:
for k=1:nbits
bin(k)=secret(sindx+k-1);
end
So, bin will be undefined. So, the error happens. This is one of the cases where the error can happen. There are many such possible cases.