Structured text seems to delight in making the simple really difficult (much more used to C). Could somebody please rearrange this so it will compile.
VAR_GLOBAL
ErrorStg : Array[0 .. 10] of STRING[16] := "Good","Bad","Fsked";
END_VAR
Did you read the compiler error at all...?
The working version at least on CODESYS 3 based platforms:
ErrorStg : ARRAY[0 .. 10] OF STRING[16] := ['Good','Bad','Fsked'];
The working version at least on CODESYS 2 based platforms:
ErrorStg : ARRAY[0 .. 10] OF STRING[16] := 'Good', 'Bad', 'Fsked';
You should use ' instead of " with regular strings.
When you initialize an array on the definition line, you have to give all of the values (all 11 in your case).
As an alternative, I would suggest a much easier solution - use an init routine to assign the values. If you are opposed to “burning boot time”, you can still solve by defining a FB called InitGlobals and then define a FB_INIT method and put your assignments there. FB_INIT executes as soon as the object exists and not when your program runs. Add an instance of InitGlobals to your code, of course.
Related
Reading through https://docs.perl6.org/language/packages#Package-qualified_names it outlines qualifying package variables with this syntax:
Foo::Bar::<$quux>; #..as an alternative to Foo::Bar::quux;
For reference the package structure used as the example in the document is:
class Foo {
sub zape () { say "zipi" }
class Bar {
method baz () { return 'Þor is mighty' }
our &zape = { "zipi" }; #this is the variable I want to resolve
our $quux = 42;
}
}
The same page states this style of qualification doesn't work to access &zape in the Foo::Bar package listed above:
(This does not work with the &zape variable)
Yet, if I try:
Foo::Bar::<&zape>; # instead of &Foo::Bar::zape;
it is resolves just fine.
Have I misinterpreted the document or completely missed the point being made? What would be the logic behind it 'not working' with code reference variables vs a scalar for example?
I'm not aware of differences, but Foo::Bar::<&zape> can also be modified to use {} instead of <>, which then can be used with something other than literals, like this:
my $name = '&zape';
Foo::Bar::{$name}()
or
my $name = 'zape';
&Foo::Bar::{$name}()
JJ and Moritz have provided useful answers.
This nanswer is a whole nother ball of wax. I've written and discarded several nanswers to your question over the last few days. None have been very useful. I'm not sure this is either but I've decided I've finally got a first version of something worth publishing, regardless of its current usefulness.
In this first installment my nanswer is just a series of observations and questions. I also hope to add an explanation of my observations based on what I glean from spelunking the compiler's code to understand what we see. (For now I've just written up the start of that process as the second half of this nanswer.)
Differences (if any) between Package::<&var> vs &Package::var?
They're fundamentally different syntax. They're not fully interchangeable in where you can write them. They result in different evaluations. Their result can be different things.
Let's step thru lots of variations drawing out the differences.
say Package::<&var>; # compile-time error: Undeclared name: Package
So, forget the ::<...> bit for a moment. P6 is looking at that Package bit and demanding that it be an already declared name. That seems simple enough.
say &Package::var; # (Any)
Quite a difference! For some reason, for this second syntax, P6 has no problem with those two arbitrary names (Package and var) not having been declared. Who knows what it's doing with the &. And why is it (Any) and not (Callable) or Nil?
Let's try declaring these things. First:
my Package::<&var> = { 42 } # compile-time error: Type 'Package' is not declared
OK. But if we declare Package things don't really improve:
package Package {}
my Package::<&var> = { 42 } # compile-time error: Malformed my
OK, start with a clean slate again, without the package declaration. What about the other syntax?:
my &Package::var = { 42 }
Yay. P6 accepts this code. Now, for the next few lines we'll assume the declaration above. What about:
say &Package::var(); # 42
\o/ So can we use the other syntax?:
say Package::<&var>(); # compile-time error: Undeclared name: Package
Nope. It seems like the my didn't declare a Package with a &var in it. Maybe it declared a &Package::var, where the :: just happens to be part of the name but isn't about packages? P6 supports a bunch of "pseudo" packages. One of them is LEXICAL:
say LEXICAL::; # PseudoStash.new(... &Package::var => (Callable) ...
Bingo. Or is it?
say LEXICAL::<&Package::var>(); # Cannot invoke this object
# (REPR: Uninstantiable; Callable)
What happened to our { 42 }?
Hmm. Let's start from a clean slate and create &Package::var in a completely different way:
package Package { our sub var { 99 } }
say &Package::var(); # 99
say Package::<&var>(); # 99
Wow. Now, assuming those lines above and trying to add more:
my Package::<&var> = { 42 } # Compile-time error: Malformed my
That was to be expected given our previous attempt above. What about:
my &Package::var = { 42 } # Cannot modify an immutable Sub (&var)
Is it all making sense now? ;)
Spelunking the compiler code, checking the grammar
1 I spent a long time trying to work out what the deal really is before looking at the source code of the Rakudo compiler. This is a footnote covering my initial compiler spelunking. I hope to continue it tomorrow and turn this nanswer into an answer this weekend.
The good news is it's just P6 code -- most of Rakudo is written in P6.
The bad news is knowing where to look. You might see the doc directory and then the compiler overview. But then you'll notice the overview doc has barely been touched since 2010! Don't bother. Perhaps Andrew Shitov's "internals" posts will help orient you? Moving on...
In this case what I am interested in is understanding the precise nature of the Package::<&var> and &Package::var forms of syntax. When I type "syntax" into GH's repo search field the second file listed is the Perl 6 Grammar. Bingo.
Now comes the ugly news. The Perl 6 Grammar file is 6K LOC and looks super intimidating. But I find it all makes sense when I keep my cool.
Next, I'm wondering what to search for on the page. :: nets 600+ matches. Hmm. ::< is just 1, but it is in an error message. But in what? In token morename. Looking at that I can see it's likely not relevant. But the '::' near the start of the token is just the ticket. Searching the page for '::' yields 10 matches. The first 4 (from the start of the file) are more error messages. The next two are in the above morename token. 4 matches left.
The next one appears a quarter way thru token term:sym<name>. A "name". .oO ( Undeclared name: Package So maybe this is relevant? )
Next, token typename. A "typename". .oO ( Type 'Package' is not declared So maybe this is relevant too? )
token methodop. Definitely not relevant.
Finally token infix:sym<?? !!>. Nope.
There are no differences between Package::<&var> and &Package::var.
package Foo { our $var = "Bar" };
say $Foo::var === Foo::<$var>; # OUTPUT: «True»
Ditto for subs (of course):
package Foo { our &zape = { "Bar" } };
say &Foo::zape === Foo::<&zape>;# OUTPUT: «True»
What the documentation (somewhat confusingly) is trying to say is that package-scope variables can only be accessed if declared using our. There are two zapes, one of them has got lexical scope (subs get lexical scope by default), so you can't access that one. I have raised this issue in the doc repo and will try to fix it as soon as possible.
In the Hash documentation, the section on Object keys seems to imply that you can use any type as a Hash key as long as you indicate but I am having trouble when trying to use an array as the key:
> my %h{Array};
{}
> %h{[1,2]} = [3,4];
Type check failed in binding to parameter 'key'; expected Array but got Int (1)
in block <unit> at <unknown file> line 1
Is it possible to do this?
The [1,2] inside the %h{[1,2]} = [3,4] is interpreted as a slice. So it tries to assign %h{1} and %{2}. And since the key must be an Array, that does not typecheck well. Which is what the error message is telling you.
If you itemize the array, it "does" work:
my %h{Array};
%h{ $[1,2] } = [3,4];
say %h.perl; # (my Any %{Array} = ([1, 2]) => $[3, 4])
However, that probably does not get what you want, because:
say %h{ $[1,2] }; # (Any)
That's because object hashes use the value of the .WHICH method as the key in the underlying array.
say [1,2].WHICH; say [1,2].WHICH;
# Array|140324137953800
# Array|140324137962312
Note that the .WHICH values for those seemingly identical arrays are different.
That's because Arrays are mutable. As Lists can be, so that's not really going to work.
So what are you trying to achieve? If the order of the values in the array is not important, you can probably use Sets as keys:
say [1,2].Set.WHICH; say [1,2].Set.WHICH
# Set|AEA2F4CA275C3FE01D5709F416F895F283302FA2
# Set|AEA2F4CA275C3FE01D5709F416F895F283302FA2
Note that these two .WHICHes are the same. So you could maybe write this as:
my %h{Set};
dd %h{ (1,2).Set } = (3,4); # $(3, 4)
dd %h; # (my Any %{Set} = ((2,1).Set) => $(3, 4))
Hope this clarifies things. More info at: https://docs.raku.org/routine/WHICH
If you are really only interested in use of an Object Hash for some reason, refer to Liz's answer here and especially the answers to, and comments on, a similar earlier question.
The (final1) focus of this answer is a simple way to use an Array like [1,'abc',[3/4,Mu,["more",5e6],9.9],"It's {<sunny rainy>.pick} today"] as a regular string hash key.
The basic principle is use of .perl to approximate an immutable "value type" array until such time as there is a canonical immutable Positional type with a more robust value type .WHICH.
A simple way to use an array as a hash key
my %hash;
%hash{ [1,2,3].perl } = 'foo';
say %hash{ [1,2,3].perl }; # displays 'foo'
.perl converts its argument to a string of Perl 6 code that's a literal version of that argument.
say [1,2,3].perl; # displays '[1, 2, 3]'
Note how spaces have been added but that doesn't matter.
This isn't a perfect solution. You'll obviously get broken results if you mutate the array between key accesses. Less obviously you'll get broken results corresponding to any limitations or bugs in .perl:
say [my %foo{Array},42].perl; # displays '[(my Any %{Array}), 42]'
1 This is, hopefully, the end of my final final answer to your question. See my earlier 10th (!!) version of this answer for discussion of the alternative of using prefix ~ to achieve a more limited but similar effect and/or to try make some sense of my exchange with Liz in the comments below.
I have a data frame DF which contains numerous variables. Each variable is present twice because I am conducting an analysis of "couples".
Among others, DF has a series of indicators of diversity :
DF$div1.1, DF$div2.1, .... , DF$divN.1, DF$div.1.2, ..., DF$divN.2
Similarly, it has a series of indicators of another characteristic:
DF$char1.1, DF$char2.1, .... , DF$charM.1, DF$char.1.2, ..., DF$charM.2
Here's a link to an example of DF: http://shorttext.com/5d90dd64
Each time the ".1", ".2" stand for the couple member considered.
My goal:
For each indicator divI and charJ, I want to create another variable DF$divchar that takes the value DF$divI.1 when DF$charJ.1>DF$charJ.2; and DF$divI.2 when DF$charJ.1<DF$charJ.2.
Here is the solution I came up with, it seems somehow very intricate and sometimes behaves in strange ways:
I created a series of binary variables that take the value one if DF$charJ.1>DF$charJ.2. The are stored under DF$CharMax.1.
Here's how I created it:
DF$CharMax.1 <- as.data.frame(
sapply(1:length(nam),
function(n)
as.numeric(DF[names(DF)==names.1[n]]
>DF[names(DF)==names.2[n]])
))
I created the function BinaryExtract:
BinaryExtract <- function(var1, var2, extract) {var1*extract +var2*(1-extract)}
I created the matrix NameFull that contains all the possible combinations of div and char, separated with "YY"
NameFull <- sapply(c("div1",...,"divN")
, function(nam) paste(nam, names(DF$YMax.1), sep="YY")
And then I create all my variables:
DF[, as.vector(NameFull)] <- lapply(as.vector(NameFull), function(e)
BinaryExtract(DF[,paste0(unlist(strsplit(e,"YY"))[1],".1")]
, DF[, paste0(unlist(strsplit(e,"YY"))[1],".1")]
, DF$charMax.1[unlist(strsplit(e,"YY"))[2]]))
My Problem
A. It looks like a very complicated solution for something that simple. What am I missing?
B. Moreover, when I print DF, just typing DF in the command window, I do not see the variables NameFull. They seem to appear with the names of char.
Here's what I get: http://shorttext.com/5d9102c
Similarly, I have tried to change all their names to get rid of the "YY" and it does not seem to work:
names(DF[, as.vector(NameFull)]) <- as.vector(c("div1",...,"divN"), sapply(, function(nam)
paste(nam, names(DF$YMax.1), sep=".")))
When I look at names(DF), I keep getting the old names with the "YY"
However, I do get a result if I explicitly call for them
> DF[,"divIYYcharJ"]
I would really appreciate any suggestion, comment and explanation. I am quite new to R ad was more used to Stata. I feel there is something deeply inefficient here. Thanks
Is it possible to a)define b)initialize a new multidimensional array using an existing array, like in following code instead of var b [2][3]int, just saying something like var b [2]a ?
Using a's type whatever it is, instead of hardcoding it (which misses the point of using [...] for a).
And perhaps handling initialization=copying of values at the same time?
package main
func main () {
a := [...]int{4,5,6}
var b [2][3]int
b[0],b[1] = a,a
}
(I'm aware of ease and convenience of slices, but this question is about understanding arrays.)
Edit: can't believe I forgot about var b [2][len(a)]int, beginner's brain freeze. One line answer would be var b = [2][len(a)]int{a,a} . That's a type conversion, right?
The following code would also work. Both your example and mine do the same thing and neither should be much faster than the other.
Unless you use reflect to make a slice (not array) of your [3]int, it is impossible to not repeat [3]int in your new type. Even that is not possible in the current release. It is in tip and will be released in Go 1.1.
package main
import "fmt"
func main() {
a := [...]int{4,5,6}
var b = [2][3]int{a, a}
fmt.Println(b)
}
I am attempting to locate the nth element of a List in Prolog. Here is the code I am attempting to use:
Cells = [OK, _, _, _, _, _] .
...
next_safe(_) :-
facing(CurrentDirection),
delta(CurrentDirection, Delta),
in_cell(OldLoc),
NewLoc is OldLoc + Delta,
nth1(NewLoc, Cells, SafetyIdentifier),
SafetyIdentifier = OK .
Basically, I am trying to check to see if a given cell is "OK" to move into. Am I missing something?
there is a predfined predicate called nth0 ..
5 ?- nth0(1,[1,2,3],X).
X = 2.
6 ?- listing(nth0).
lists:nth0(A, B, C) :-
integer(A), !,
A>=0,
nth0_det(A, B, C).
lists:nth0(A, B, C) :-
var(A), !,
nth_gen(B, C, 0, A).
true.
index listing start from 0
hope this helps ..
Louis, I'm not entirely clear on what you're aiming to do with this code, but a couple of comments that might hopefully help.
Things that start with a capital letter in Prolog are variables to be matched against in rules. _ is a special symbol that can be used in place of a variable name to indicate that any value can match.
next_safe(_) is therefore only capable of providing you with a true/false answer if you give it a specific value. One of the major benefits of Prolog is the ability to unify against a variable through backtracking (as ony said). This would mean that when written correctly you could just ask Prolog next_safe(X). and it would return all the possible values (safe moves) that unify with X.
To go back to the first point about capital letters. This means that OK is actually a variable waiting to be matched. It is effectively an empty box that you are trying to match against another empty box. I think what you're intending is to use the value ok which is different. You do not assign to variables in the same way that you do in other programming styles. Something like the following might be closer to what you are looking for, though I'm still not sure it's right as it looks like you're trying to assign things but I'm not certain how your nth1 works.
Cells = [ok, _, _, _, _, _] .
...
next_safe(NewLoc) :-
facing(CurrentDirection),
delta(CurrentDirection, Delta),
in_cell(OldLoc),
NewLoc is OldLoc + Delta,
nth1(NewLoc, Cells, ok).