Questions tagged [comparison]
Questions about data comparison and efficient ways to accomplish it.
113
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Comparing Java objects with different member variables
I have a base class "People" which two other classes inherit from: Employee and Student. The Student class includes a GPA (type double) and the Employee class does not. I have an ArrayList ...
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Is it a common practice to compare HLDs with the source code? [closed]
We have recently completed the development of a large system (150,000 lines of code more or less) which was developed from an HLD. Our stakeholders want to take the HLD and compare it with the source ...
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460
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Best way to check for truthy values in PHP?
In PHP, there are several ways to check whether a value is true, or similar:
true === $v, only works for bool
true == $v || !!$v, works with int and string, but a non empty array can also be ...
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3
answers
180
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How to identify whether or not 2 pieces of text are identical? [closed]
Let's say I was to create a scraper. At some point I'll need to come up with algorithm of identifing whether or not a piece of a newly scraped text matches the one that's already in the DB. How would ...
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2
answers
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Isn't data migration a major benefit of MongoDB compared to the commonly used relational databases?
I was reading an old answer which was recently updated, and noticed that the author doesn't quote the simplicity of data migration as a benefit of MongoDB. I always thought that the major benefit of a ...
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Can writing Object-Orientated Code in a Functional style improve performance?
Given a scenario where you have consecutive setters or a series of events where an object is modified, can it be more performant to instead write code in a way where a new state is returned rather ...
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4
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Language design : use equals symbol = both for affectation and comparison, like in MySQL
I'm currently designing a database query language and I came to wonder what should be the best syntax for the comparison operator.
Most modern languages use ==, but amongst the database languages ...
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"REST Vs GraphQL" is it a correct comparison?
I saw in many sites that compare REST with GraphQL. after investigating this concern (actually my concern) that, "is it a correct comparison?", I being more confused.
Since the REST has a different ...
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1
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57
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Objectreference vs Equality [closed]
While coding I stumbled upon something like this (extremely simplified example):
public bool Func()
{
Object[] array = new Object[] {false, false};
return array[0] != array[1];
}
I was ...
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2
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4
answers
132
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Date comparison with the last second of a day
Would you consider
WHERE SomeDate <= '2018-01-01 23:59:59'
instead of
WHERE SomeDate < '2018-01-02'
When the intention is that SomeDate goes no further then 2018-01-01
a code smell and if ...
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1
vote
1
answer
88
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Simulating Comparison Without Using Comparison Primitives
In the same way that you can simulate the if statement and functions, I am wondering if there is a way to simulate the comparison operators ==, !=, >, >=, <, <=.
For example, in ...
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TIOBE Index: why c++ is in 3rd place and C is having more land in the last year?
Searching for c++ ranking on the TIOBE index, I was stumped to see that C is in front of C++, and from 2017, C took a leap. Could someone explain why?
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2
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Proving Two Zip file are identical
I migrated some files from one Version Control System to another. I have to prove that content are identical (between source and destination, denote 1 , 2). There are a few zips files (lets call them ...
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Is the IComparable interface outdated/"harmful"?
IComparable only works one way
Let's say you have a Employee class. In one view, you want to show all Employees sorted by name - in another, by address. How are you going to achieve that? Not with ...
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Is comparing "dollar-hours" for running a specific piece of code practical as an estimate of rented system performance?
Background: there'a a gazillion types of virtual machines in Microsoft Azure each having different performance and price. Such virtual machines are paid per hour. The goal is to decide how to get "the ...
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Best approach for name similarity
As part of validation, we perform name similarity check and allow only if the threshold is reached. I got some help from StackOverflow regarding the implementation and finally implemented JaroWinkler ...
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Why in Tournament Sorting do we neglect the number of comparisons to find the Minimum?
Here the professor said that, Tournament sort needs (n-1) + 2(n-1)logn comparisons.
{Where (n-1) for calculating Maximum or say creating Tournament structure
and
2(n-1)logn for other elements to sort}...
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1
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How does integer comparison work internally?
E.g. when comparing two integers as follows in a C-like language:
if (3 > 2) {
// do something
}
How is the judgement whether 3 is greater than 2 (true) or not (false) made internally?
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2
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What are the most idiomatic abbreviations for comparison operators [closed]
I am wondering what the most idiomatic text abbreviations for comparison operators are. I need to build a custom enum with them, so I cannot use their symbols. To me personally, these seem idiomatic:
...
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I want to write an application to compare files, similar to WinMerge. I'm not sure how to design it, though
My current project is to implement a kind of WinMerge clone to compare two files.
I am using C++ with the Win32-API (WTL, ATL, that stuff), and I already designed an UI for this. However, I am now ...
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1
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How to analyse user input and determine if it (kind of) matches an answer
I'm working on a quiz system that will allow users to enter text as an answer. The question could be something simple to start with, looking for a short phrase, or a select few words as the "correct" ...
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4
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Four-way XML comparison in C#
I have 4 XML files: A, B, C, and D. I want to know if the difference between A and B is the same as the difference between C and D.
The XML files are serializations of the same .NET object; one of ...
1
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4
answers
698
views
Comparing objects with tolerance
The following code says that c1 == c2 and c2 == c3, but c1 != c3.
TOL = 0.11
class C:
def __init__(self, x):
self.x = x
def __eq__(self, other):
return abs(self.x - other.x) ...
- 115
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57
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Is there some reason into allowing assignations in a conditional? [duplicate]
I bet I'm not the only one here that has had problems with something like this: you want to check something in a language that has the == operator for checking equality and instead you do something ...
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1
answer
212
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How do travel search engines combine flights
I'm curious about how the flight/train search engines combine the results from multiple sources. For example, let's say I'm asking to go from London to Paris, and let's assume there are no direct ...
- 119
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votes
2
answers
556
views
Algorithm for lines comparison
I'm working on the import of land-use data into Openstreetmap. Unfortunately I've encountered a problem that has delayed my time table.
Take a look at the picture below: the red line is the main road ...
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1
answer
211
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Developing a simple HTML exercises with JavaScript [closed]
I'm developing a website with some simple HTML exercises (like the ones in Codeschool and Codacademy), and now I'm stuck at the correction phase, how can I compare two HTML strings and decide if the ...
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Why do most mainstream languages not support "x < y < z" syntax for 3-way Boolean comparisons?
If I want to compare two numbers (or other well-ordered entities), I would do so with x < y. If I want to compare three of them, the high-school algebra student will suggest trying x < y < z....
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512
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How to effectively compare the (almost) same code which has been auto-formatted?
I am trying to infer the differences between two projects, however so far it has been really painful, because one of the parties has done auto-formatting on the code.
Basically, this makes a merging ...
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21
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Comparing articles from various web-stores
Today I had the idea to write a program that compares the prizes between different web-stores. The key question I am asking myself is how to find (with a high probability) the same article on another ...
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4
answers
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Avoiding Division by Zero Using Float Comparison
Source code analyzers (like SonarQube) complain about float (or double) equality comparisons because equality is a tricky thing with floats; the values compared can be the results of computations ...
- 241
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2
answers
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Efficient algorithm to merge n successive sorted arrays in place
I am developing an in-place sorting algorithm that leaves the array into a state where it is basically a succession of sorted subsequences of any size (most are bigger than log2(size(array))); then it ...
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Comparison Function Returns True or False
In my python CS class at school, we were given a true or false question as follows.
A comparison function returns either True or False.
When originally answering I thought about two things. First,...
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5
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Could an instance be equal to some other instance of a more specific type?
I've read this article: How to Write an Equality Method in Java.
Basically, it provides a solution for an equals() method that supports inheritance:
Point2D twoD = new Point2D(10, 20);
Point3D ...
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Functional programming: Compare all items in an array
In functional programming, how do I do an equality comparison of all items in an array?
I have an array of items that I want to compare, for example for equality. Is it possible to use a fold (also ...
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Algorithm to maximize pairwise comparisons using transitive property
I'm looking for some direction on building an algorithm that will maximize the number of pairwise comparisons of objects in a set using transitivity.
To explain in detail:
Suppose there are x ...
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3
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737
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Determine frequency-range that matches closest to input list of frequencies
Since this question is not about "code not working", I'm asking my first question here instead of StackOverflow. Inform me if any required information is missing from the question.
Setup:
I have two ...
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2
answers
188
views
Multi-pattern matching
I have a given byte array in C and I need to match it against several byte arrays and return true if there is any match.
I can make various memcmp's but I feel that it is very inefficient.
Do you ...
0
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1
answer
265
views
Should a comparison method ever return the same type back as it's comparing?
First, this is homework, but no, I'm not asking for anyone to do any code for me. My course start date isn't for another month (it's online), so I can't ask for clarification. I thought I'd see if ...
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Legitimate cases of having .equals() behaving inconsistently with .compareTo()?
Java documentation says it's "strongly recommended" to have them behaving consistently.
But are there legitimate cases of java/c#/python/etc Object.equals() method behaving inconsistently with the ...
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4
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List comparing techniques for faster performance
I need to cross names from two lists, and find all occurrences of one name in the other. The lists are too big, one have 50k elements and the other 400k.
For a small list I would use two foreach ...
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Compare names and the use of Levenshtein's algorithm
I need to cross names from two lists. What is the best away to compare the names? As you may expect, in one list we can have the complete name, on the other just the first and last.
Besides that, ...
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3
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Is JavaScript fail-safe?
I was compiling a list of comparison of top 10 programming languages (JavaScript included). I was doing it from this Wikipedia page.
However, in the third table (Failsafe I/O), there is no row for ...
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Comparing path strings against list of rules
I am trying to find a way to enhance a filtering algorithm. I am developing a backup software that enables users to specify custom filters to exclude unwanted files/directories.
Currently when trying ...
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4
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Why are return values from compare functions in many languages defined loosely?
Many languages define that compare functions should return ANY negative value, zero, or ANY positive value. Is there some reason that it shouldn't be clearly defined as -1 0 and 1? Does a wide range ...
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Why are mostly 9999, 99999.... are used for making comparisons [closed]
I (I am sure everyone else also) have always seen comparisons of some value to 999 or 9999 .... etc.
for e.g.:
in CSS
z-index: 9999
or some times
str.length < 99999
I wonder if there is some ...
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Algorithm to merge two sorted arrays with minimum number of comparisons
Given are two sorted arrays a, b of type T with size n and m. I am looking for an algorithm that merges the two arrays into a new array (of maximum size n+m).
If you have a cheap comparison ...
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5
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Algorithm to test file equivalence
I'm writing a program that needs to test if a file is equivalent to one or more other files. To accomplish this, every time we see a new file we stat the file and get the size.
We use the size as a ...
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Comparing doubles [duplicate]
I need to compare to double variables like this
if (distance <= radius)
both distance and radius are doubles and I remember in class how to use epsilon comparisons for checking equality but how ...
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Is there a language-agnostic specification for "string natural sorting order"?
As I painfully try to find a good natural sorting algorithm written in JavaScript, I then stumble upon a bunch of different implementations, interesting blog posts, and answers on StackOverflow.
Each ...
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