lens | A novel way of seeing content
kandi X-RAY | lens Summary
kandi X-RAY | lens Summary
Lens provides a novel way of looking at content on the web. It is designed to make life easier for researchers, reviewers, authors and readers.
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Top functions reviewed by kandi - BETA
- Creates an async iterator function .
- Call a callback
- Traverse an array
- Computes bounding rectangle s bounding boxes .
- show nodes in a graph
- Convert DOM element to DOM structure
- Returns the environment reference for the given formula
- Figure out the formula area for a given node
- Calculates and returns the bounding rect of an element .
- Returns the bounding offset of the parent element .
lens Key Features
lens Examples and Code Snippets
Lines of Code : 30
License : No License
Copypublic static int findNumberOfLIS(int[] nums) {
int len = nums.length, maxLen = 0;
if (len < 2) return len;
int[] lens = new int[len];
int[] counts = new int[len];
Arrays.fill(lens, 1);
Arrays.fill(c Community Discussions
Trending Discussions on lens
QUESTION
A type Prism' s a = Prism s s a a (hackage) can be thought of as a relation between some structure s and its member a, such that you can always produce the structure from the member (a -> s), but can only optionally retrieve the member from the structure (s -> Maybe a).
This model is helpful in relating a sum type to one of its constructors ... as well as (more relevant here) in route encoding and decoding. If s is the encoded route URL, and a is the route type, then we have a -> s representing the encoding function (always succeeds), and s -> Maybe a representing the decoding function (can fail).
Now, on to these pairs of functions, I want to add a "context" argument that is to be used in the encoding and decoding process (imagine that the decoding process needs to "look up" some database before successfully producing a relevant route). Basically:
...ANSWER
Answered 2022-Mar-15 at 15:18I'm with @HTNW. You should just be able to define:
QUESTION
I have this extremely messed up dataframe:
...ANSWER
Answered 2022-Mar-09 at 18:02Here is a way using stack. First remove the _n from the columns names, then set_index the column id, mask the cell with empty string that would be remove when stacking the data. Then use reset_index and rename to fit the expected output.
QUESTION
So I'm trying to code something to tell me the number of elements in any given compound. I'm not even sure where to start: I tried coding something but then realized that it only worked for simple compounds (or did not work at all). Here's an example of what I want:
...ANSWER
Answered 2022-Jan-31 at 12:50Try with this recursive function:
QUESTION
I am trying to access a nested record using lenses and prisms in Haskell:
...ANSWER
Answered 2022-Mar-01 at 21:09Updated: As per comments, I've fixed some errors and added a few asides in [[double square brackets]].
Here's how/why your first mMistake works...
A prism is an optic that focus on a "part" that may or may not be present in the "whole". [[Technically, it focuses on the sort of part that can be used to reconstruct an entire whole, so it really pertains to a whole that can come in several alternative forms (as in the case of a sum type), with the "part" being one of those alternative forms. However, if you're only using a prism for viewing and not setting, this added functionality isn't too important.]]
In your example, both _StateRun and _Just are prisms. The _Just prism focuses on the a part of a Maybe a whole. Such an a may or may not be present. If the Maybe a value is Just x for some x :: a, the part a is present and has value x, and that's what _Just focuses on. If the Maybe a value is Nothing, then the part a is not present, and _Just doesn't focus on anything.
It's somewhat similar for your prism _StateRun. If the whole StateStep is a StateRun x y value, then _StateRun focuses on that "part", represented as a tuple of the fields of the StateRun constructor, namely (x, y) :: (Int, Maybe Text). On the other hand, if the whole StateStep is a StatePause, that part isn't present, and the prism doesn't focus on anything.
When you compose prisms, like _StateRun and _Just, and lenses, like stStep and _2, you create a new optic that combines the composed series of focusing operations.
[[As was pointed out in the comments, this new optic isn't a prism; it's "only" traversal. In fact, it's a specific kind of traversal, called an "affine traversal". A run-of-the-mill traversal can focus on zero or more parts, while an affine traversal focuses on exactly zero (part not present) or one (unique part present). The lens library doesn't make the distinction between affine traversals and other sorts of traversals, though. The reason the new optic is "only" an affine traversal instead of a prism relates to that earlier technical point. Once you add lenses, you remove your ability to reconstruct the entire "whole" from a single "part". Again, if you're only using the optics for viewing, not setting, it won't really matter.]]
Anyway, consider the optic (affine traversal):
QUESTION
First time using lens. set and over went easy enough and I thought it would be simple with view: Use the same scheme to reference the inner part, but don't supply a new value or function. But Noooo. tst3 below gives the error below the code. Anyone know what's going on?
ANSWER
Answered 2022-Feb-20 at 23:35ix 0 doesn't produce a lens, but a traversal.1
Informally, a lens is a "path" that will definitively reach a single value (if you follow it within a hypothetical larger value). A traversal is a path to zero or more values. You can set or view the single target of a lens. And you can set the zero or more targets of a traversal (this simply updates all of them that are present, which is a no-op if there are zero present). But viewing the targets of a traversal is less straightforward.
If view simply took a traversal, and an outer structure, and gave you the target value, then it would have a problem. If there are multiple targets, how should it decide which to return? And if there are zero targets, it can't return anything; it would have to be partial. What it needs is a way of condensing zero-or-more values into a single value, so it can return that. And the Monoid class provides exactly the facilities to do that; mempty for if there aren't any targets at all, and <> to condense multiple values to a single one. So view with a traversal2 actually requires a Monoid constraint on the returned type, and that's why you're getting the complaint about No instance for (Monoid Int) arising from a use of `ix'.
And in case it isn't clear, you can often compose (with .) different types of optics (the general term for "lens-ish things", including lenses, traversals, and several others). But the result has the capabilities of the least capable of the two inputs. So even though your inner and w are full lenses, composing them with a traversal produced by ix results in a traversal, not a lens.
But in this case you know that you're using ix. The specific kind of traversals ix makes end up having zero or one target, rather than the zero or more targets that traversals have in general. So you could use preview instead of view; for a traversal it will produce a Maybe containing Just the first target of the traversal, or Nothing if there weren't any. A Maybe is exactly what the type system deems appropriate here, since ix can't guarantee there will be a target value, but there won't be more than one.
In my experience, when I try to view something and get this Monoid instance error, it almost always means I have an optic that can't guarantee a result and I should actually be using preview to get a Maybe.
Simple example:
QUESTION
I used the blowup.js plugin as a base, and I am trying to rotate the image, and the lens to follow the rotation. But it is not working.
When I put the rotate(180deg) for example, the lens and the image are mismatched, if I remove the rotate(180deg) they are aligned.
Anybody know how to help me?
...ANSWER
Answered 2022-Feb-16 at 17:42You might rotate the lens in the opposite direction (-180deg) and inverse background position too:
Side note: you don't want to apply background-image on every mousemove, move it to the lens init.
QUESTION
here is a puzzle that I keep on bumping into and that, I believe, no previous SO question has been addressing: How can I best use the lens library to set or get values within a State monad managing a nested data structure that involves Maps when I know for a fact that certain keys are present in the maps involved?
ANSWER
Answered 2022-Feb-09 at 11:43If you are sure that the key is present then you can use fromJust to turn the Maybe User into a User:
QUESTION
I am working on this problem on CSES, Traffic Lights:
There is a street of length 𝑥 whose positions are numbered 0,1,…,𝑥. Initially there are no traffic lights, but 𝑛 sets of traffic lights are added to the street one after another.
Your task is to calculate the length of the longest passage without traffic lights after each addition.
InputThe first input line contains two integers 𝑥 and 𝑛: the length of the street and the number of sets of traffic lights.
Then, the next line contains n integers 𝑝1,𝑝2,…,𝑝𝑛: the position of each set of traffic lights. Each position is distinct.
OutputPrint the length of the longest passage without traffic lights after each addition.
ConstraintsExample
- 1 ≤ 𝑥 ≤ 109
- 1 ≤ 𝑛 ≤ 2⋅105
- 0 < 𝑝𝑖 < 𝑥
Input:
...
ANSWER
Answered 2022-Jan-11 at 10:06The data structure you have for lens is like a multiset, also available as Counter. The part of your algorithm that is the bottle neck in terms of time complexity, is this:
QUESTION
While trying to apply a function with multiple layers of functors to a member of a host data structure, as in the following example:
...ANSWER
Answered 2021-Dec-29 at 00:09Not much of a standard approach, perhaps, but anyway: alaf can handle the Compose wrapping. For instance:
QUESTION
I am trying to generate lens for data type with a lens field.
...ANSWER
Answered 2021-Nov-26 at 22:00{-# Language ImpredicativeTypes #-}
{-# Language TypeApplications #-}
-- ..
st_lens :: forall st l. Lens' (St st l) (Lens' st l)
st_lens = lens @_ @(Lens' st l) _st_lens \s a -> s { _st_lens = a }
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