semantics

Partial matching of function argument

余生长醉 提交于 2019-11-26 23:03:09
I know that for a list, partial matching is done when indexing using the basic operators $ and [[ . For example: ll <- list(yy=1) ll$y [1] 1 But I am still an R newbie and this is new for me, partial matching of function arguments: h <- function(xx=2)xx h(x=2) [1] 2 I want to understand how this works. What is the mechanism behind it? Does this have any side effects? I want understand how can someone test if the xx argument was given? Edit after Andrie comment: Internally R uses pmatch algorithm to match argument, here an example how this works: pmatch("me", c("mean", "median", "mode")) #

What does the colon dash “:-” mean in bash [duplicate]

懵懂的女人 提交于 2019-11-26 22:56:15
问题 This question already has an answer here: Usage of :- (colon dash) in bash 2 answers The result is the one desired; after a bit of trial and error. I don't understand what the "2:-" and "3:-" do/mean. Can someone explain. #!/bin/bash pid=$(ps -ef | grep java | awk ' NR ==1 {print $2}') count=${2:-30} # defaults to 30 times delay=${3:-10} # defaults to 10 second mkdir $(date +"%y%m%d") folder=$(date +"%y%m%d") while [ $count -gt 0 ] do jstack $pid >./"$folder"/jstack.$(date +%H%M%S.%N) sleep

when to use UL or OL in html?

前提是你 提交于 2019-11-26 22:50:18
问题 Seems interchangable? 回答1: UL means "unordered list". OL means "ordered list". UL gets you bullet points. OL gets you numbers. Definitely not interchangable. 回答2: In math terms (hey, why not?), an <ol> represents a sequence, whereas <ul> represents a set. Rearranging the items in an ordered list changes the list's meaning. Rearranging them in an unordered list does not. This is a good rule-of-thumb for which type of list to use. If changing the order of the items makes the list incorrect, you

LSA - Latent Semantic Analysis - How to code it in PHP?

狂风中的少年 提交于 2019-11-26 22:46:57
问题 I would like to implement Latent Semantic Analysis (LSA) in PHP in order to find out topics/tags for texts. Here is what I think I have to do. Is this correct? How can I code it in PHP? How do I determine which words to chose? I don't want to use any external libraries. I've already an implementation for the Singular Value Decomposition (SVD). Extract all words from the given text. Weight the words/phrases, e.g. with tf–idf. If weighting is too complex, just take the number of occurrences.

What is collection semantics (in .NET)?

谁说我不能喝 提交于 2019-11-26 22:25:41
问题 I need to maintain collection semantics in my own class. Couldn't you explain, what is the collection semantics? As I understand, it is a set of some interfaces that must be implemented in a class. Is it true? And if yes – what exactly must I implement in the class and why ? Are these two interfaces – ICollection and IEnumerable – enough, or these are only the most necessary ones? I am programming a circular linked list using this article as help. 回答1: There are many collection types in .NET,

Which is more correct: <h1><a>…</a></h1> OR <a><h1>…</h1></a>

时光怂恿深爱的人放手 提交于 2019-11-26 21:59:46
Are both <h1><a ...> ... </a></h1> and <a ...><h1> ... </h1></a> valid HTML, or is only one correct? If they are both correct, do they differ in meaning? Marco Both versions are correct. The biggest difference between them is that in the case of <h1><a>..</a></h1> only the text in the title will be clickable. If you put the <a> around the <h1> and the css display property is block (which it is by default) the entire block (the height of the <h1> and 100% of the width of the container the <h1> resides in) will be clickable. Historically you could not put a block element inside of an inline

Simultaneous assignment semantics in Python

谁说胖子不能爱 提交于 2019-11-26 20:41:15
问题 Consider the following Python 3 code: a = [-1,-1,-1] i = 0 And now consider the following two versions of a simultaneous assignment over both a and i: Assignment version 1: a[i],i = i,i+1 Assignment version 2: i,a[i] = i+1,i I would expect these two versions of simultaneous assignments to be semantically equivalent. However, if you check the values of a and i after each one of the simultaneous assignments, you get different states: Output for print(a,i) after assignment version 1: [0, -1, -1]

Are parentheses around the result significant in a return statement?

心已入冬 提交于 2019-11-26 19:42:52
Is there a difference between these two statements inside a function? bool returnValue = true; //Code that does something return(returnValue); and this? bool returnValue = true; //Code return returnValue; The former has parentheses around returnValue . Michael Petch As of C++14, they often are. C++14 adds a fringe case where parentheses around a return value may alter the semantics. This code snippet shows two functions being declared. The only difference is parentheses around the return value. int var1 = 42; decltype(auto) func1() { return var1; } // return type is int, same as decltype(var1)

Is there an algorithm that tells the semantic similarity of two phrases

亡梦爱人 提交于 2019-11-26 19:25:01
input: phrase 1, phrase 2 output: semantic similarity value (between 0 and 1), or the probability these two phrases are talking about the same thing Matt Mower You might want to check out this paper: Sentence similarity based on semantic nets and corpus statistics (PDF) I've implemented the algorithm described. Our context was very general (effectively any two English sentences) and we found the approach taken was too slow and the results, while promising, not good enough (or likely to be so without considerable, extra, effort). You don't give a lot of context so I can't necessarily recommend

Computed read-only property vs function in Swift

两盒软妹~` 提交于 2019-11-26 19:00:58
问题 In the Introduction to Swift WWDC session, a read-only property description is demonstrated: class Vehicle { var numberOfWheels = 0 var description: String { return "\(numberOfWheels) wheels" } } let vehicle = Vehicle() println(vehicle.description) Are there any implications to choosing the above approach over using a method instead: class Vehicle { var numberOfWheels = 0 func description() -> String { return "\(numberOfWheels) wheels" } } let vehicle = Vehicle() println(vehicle.description()