I have a list
var theDataList: List<Data> // populated with some data
and made a copy of it
val copy = theDataList.toMutableList()
downstream in the code it would like to verify whether it is the copy one or the original one
the .hashCode() returns same for both
If just want to use Log to print out, how to do it?
the Log.d("+++", "theDataList: ${theDataList.hashCode()}, copy: ${copy.hashCode()"}) print out same number.
And Log.d("+++", "copy: ${copy}") prints out the list content
Problem:
The hash code for both lists is the same because it is based on the data in the list, which is the same.
Solution:
What you actually want is to compare the references of both lists. You can do that with Kotlin's referential equality operator ===.
theDataList === copy // false
There is no ID/hash you can rely on to identify an object on the JVM the way you want. For more info take a look here.
Use the === operator to compare references are the same (not calling equals method)
Related
Given a list of arbitrary objects
input = listOf(a, b, c, a)
... is there a function (with one non-collection argument) in the Kotlin standard library that I can use to make a copy of this list, removing all instances of ONE object?
Something like:
val filtered = input.removeAllInstancesOf(a)
To clarify, I'm aware of other (potential) solutions to this task:
Using the filter function to do this. → val output = input.filterNot { it == a }
Using the minus function with a collection → val output = input.minus(listOf(a))
Using the minus function with a non-collection argument → val output = input.minus(a) ← Only removes the first instance of a!
Removing all instances from a mutable list.
Writing such a function. → Wrap any of the above.
... but I'm wondering why I can't find a function which takes just ONE, non-collection value.
but I'm wondering why I can't find a function which takes just ONE, non-collection value.
Because that's a hyper-specific use-case of the already existing filter function. As you yourself showed it can be done in one line, and is probably the first thing a Kotlin dev would try to do (at least I would). So adding new function to the standard library probably doesn't add much value.
I am trying to assign the value of this stucture path to a fieldsymbol, but this path does not work because it has a table in it's path.
But with in the debugger this value of this path is shown correctly.
Is there a way to dynamically assign a component of a table line to a fieldsymbol, by passing one path?
If not then I will just read the table line and then use the path to get the wanted value.
ls_struct (Struct)
- SUPPLYCHAINTRADETRANSACTION (Struct)
- INCL_SUPP_CHAIN_ITEM (Table)
- ASSOCIATEDDOCUMENTLINEDOCUMENT (Element)
i_component_path = |IG_DDIC-SUPPLYCHAINTRADETRANSACTION-INCL_SUPP_CHAIN_ITEM[1]-ASSOCIATEDDOCUMENTLINEDOCUMENT|.
ASSIGN (i_component_path) TO FIELD-SYMBOL(<lg_value>).
IF <lg_value> IS NOT ASSIGNED.
return.
ENDIF.
<lg_value> won't be assigned
Solution by Sandra Rossi
The debugger has its own syntax and own logic, it doesn't apply the ASSIGN algorithm at all. With ABAP source code, you have to use ASSIGN twice, the first one to reach the internal table, then you select the first line, and the second one to reach the component of the line.
The debugger works completely differently, the debugger code works only in debug mode, you can't call the code from the debugger (i.e. if you call it, the kernel code used by the debugger will fail). No, there's no "abappath". There are the XSL transformation objects (xpath), but it's slow for what you ask.
Thank you very much
This seems to be a rather unexpected limitation of the ASSIGN statement. Probably worth a ticket to SAP's ABAP language group to clarify whether it's even a bug.
While this works:
ASSIGN data-some_table[ 1 ]-some_field TO FIELD-SYMBOL(<lv_source>).
the same expressed as a string doesn't:
ASSIGN (`data-some_table[ 1 ]-some_field`) TO FIELD-SYMBOL(<lv_source>).
Alternative 1 for (name) of the ABAP keyword documentation for the ASSIGN statement says that "[t]he name in name is structured in the same way as if specified directly".
However, this declaration is immediately followed by "the content of name must be the name of a data object which may contain offsets and lengths, structure component selectors, and component selectors for assigning structured data objects and attributes in classes or objects", a list that does not include the table expressions we would need here.
Let's say I want to connect to two package repositories, make a query for a package name, combine the result from the repos and process it (filter, unique, prioritize,...), What is a good way to do that?
What I though about is creating Array of two Cro::HTTP::Client objects (with base-uri specific to each repo), and when I need to make HTTP request I call #a>>.get, then process the result from the repos together.
I have attached a snippet of what I'm trying to do. But I would like to see if there is a better way to do that. or if the approach mention in the following link is suitable for this use case! https://perl6advent.wordpress.com/2013/12/08/day-08-array-based-objects/
use Cro::HTTP::Client;
class Repo {
has $.name;
has Cro::HTTP::Client $!client;
has Cro::Uri $.uri;
has Bool $.disable = False;
submethod TWEAK () {
$!client = Cro::HTTP::Client.new(base-uri => $!uri, :json);
}
method get (:$package) {
my $path = <x86_64?>;
my $resp = await $!client.get($path ~ $package);
my $json = await $resp.body;
return $json;
}
}
class AllRepos {
has Repo #.repo;
method get (:$package) {
# check if some repos are disabled
my #candidate = #!repo>>.get(:$package).unique(:with(&[eqv])).flat;
# do furthre processign of the data then return it;
return #candidate;
}
}
my $repo1 = Repo.new: name => 'repo1', uri => Cro::Uri.new(:uri<http://localhost:80>);
my $repo2 = Repo.new: name => 'repo2', uri => Cro::Uri.new(:uri<http://localhost:77>);
my #repo = $repo1, $repo2;
my $repos = AllRepos.new: :#repo;
#my #packages = $repos.get: package => 'rakudo';
Let's say I want to connect to two package repositories, make a query for a package name, combine the result from the repos and process it (filter, unique, prioritize,...), What is a good way to do that?
The code you showed looks like one good way in principle but not, currently, in practice.
The hyperoperators such as >>:
Distribute an operation (in your case, connect and make a query) ...
... to the leaves of one or two input composite data structures (in your case the elements of one array #!repo) ...
... with logically parallel semantics (by using a hyperoperator you are declaring that you are taking responsibility for thinking that the parallel invocations of the operation will not interfere with each other, which sounds reasonable for connecting and querying) ...
... and then return a resulting composite data structure with the same shape as the original structure if the hyperoperator is a unary operator (which applies in your case, because you applied >>, which is an unary operator which takes a single argument on its left, so the result of the >>.get is just a new array, just like the input #!repo) or whose shape is the hyper'd combination of the shapes of the pair of structures if the hyperoperator is a binary operator, such as >>op<< ...
... which can then be further processed (in your case it is, with .unique, which will produce a resulting Seq) ...
... whose elements you then assign back into another array (#candidate).
So your choice is a decent fit in principle, but the commitment to parallelism is only semantic and right now the Rakudo compiler never takes advantage of it, so it will actually run your code sequentially, which presumably isn't a good fit in practice.
Instead I suggest you consider:
Using map to distribute an operation over multiple elements (in a shallow manner; map doesn't recursively descend into a deep structure like the hyperoperators, deepmap etc., but that's OK for your use case) ...
... in combination with the race method which parallelizes the method it proceeds.
So you might write:
my #candidate =
#!repo.hyper.map(*.get: :$package).unique(:with(&[eqv])).flat;
Alternatively, check out task 94 in Using Perl 6.
if the approach mention in the following link is suitable for this use case! https://perl6advent.wordpress.com/2013/12/08/day-08-array-based-objects/
I don't think so. That's about constructing a general purpose container that's like an array but with some differences to the built in Array that are worth baking into a new type.
I can just about imagine such things that are vaguely related to your use case -- eg an array type that automatically hyper distributes method calls invoked on it, if they're defined on Any or Mu (rather than Array or List), i.e. does what I described above but with the code #!repo.get... instead of hyper #!repo.map: *.get .... But would it be worth it (assuming it would work -- I haven't thought about it beyond inventing the idea for this answer)? I doubt it.
More generally...
It seems like what you are looking for is cookbook like material. Perhaps a question posted at the reddit sub /r/perl6 is in order?
I've used dictionaries (Whether they were called that or not) in a number of other languages, but there's always been a method that can be called with on parameter that either:
A) Returns the associated value if the parameter is in use as a key, or
B) Indicates in some way that the parameter is not used as a key
I've been forced into a position where I have to learn excel/VBA and used the collections class for all of about five minutes before the lack of an .exists method led me to look for something else. The general consensus seems to be that the scripting.Dictionary class is the VBA equivalent of associative arrays/dictionaries/hashtables in other languages.
The one thing I don't like the look of though is that the only way I can see of retrieving the value associated with a given key is to use the .items property (either explicitly, or via scripting.Dictionary("key")). But rather than doing anything to indicate the issue if key is not in use in the dictionary, it adds it.
I know I can use a if structure with .exists being the test to achieve the same functionality, and can write my own function that raises an error if the exists test fails, but it seems a lot of stuffing around to achieve what is core functionality in Python (raises KeyError), PHP (raises a Notice), Java (Maps return null - although that is not necessarily ideal in the case of HashMaps where null actually is a valid value - but it does work as an indicator for HashTables).
So is there any way of attempting to retrieve a value by key that will do something (ideally throw an error) if the key is not in use, rather than silently adding it? Google hasn't provided any answers - but maybe I'm just not phrasing the search well.
I find it inconvenient too that Dictionary adds the key when you access a non-existing key.
Just use Collection and write the missing Exist function yourself, e.g.
Function ExistsInCollection(ByVal c As Collection, ByVal key As Variant) As Boolean
On Error GoTo not_exists
c.Item key
ExistsInCollection = True
not_exists:
End Function
How can I check if some fields in my word have errors? I have a large document that contains many references to other chapters or images. When those chapters or images are missing in the document, the fields containing those references will display Error! Reference Source Not Found instead of the reference.
The problem is, that I need to create an algorithm that will check for those reference errors, no matter what the locale and language of the file is. The problem is, that this field error is localized in the language of the system of the user who uses the word.
How can I do this? Is there any property on Field that can be used to check if the source is available?
Currently, I check for errors in the fields by using the result text of the field:
Int32 fieldErrors = 0;
foreach (Word.Field field in doc.Fields)
{
field.Update();
if (field.Result.Text.StartsWith("Error!"))
++fieldErrors;
}
Unfortunately, this will only work in english word instances.
In the documentation for Field types it is seen that a Field instance has an Update() method that returns a bool. The documentation does not state what the semantic meaning of the return value is, however, by doing a short empirical study I found that the method returns true if the Update() succeeded and false if the update did not succeed. This means that in order to find fields with errors you can do something like:
var fieldsWithErrors = new List<Field>();
foreach (Field field in document.Fields)
{
if(!field.Update())
fieldsWithErrors.Add(field);
}
... or shorter with LINQ:
var fieldsWithErrors = document.Fields.Cast<Field>().Where(field => !field.Update()).ToList();
Another (and faster) approach would be to use the Update() method exposed by the Fields collection.
var indexOfFirstError = document.Fields.Update();
... the method returns the index of the first field with an error. If no errors are found, the method returns 0.
For complete documentation please see the MSDN references:
Field.Update()
Fields.Update()
Field members
Fields members