# Tagged Questions

Questions about data comparison and efficient ways to accomplish it.

76 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 ...
86 views

### 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 ...
1k views

### 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....
104 views

### 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 ...
14 views

### 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 ...
266 views

### 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 ...
345 views

### 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 ...
146 views

### 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. ...
2k views

### 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 ...
216 views

### 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 ...
131 views

### 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 ...
158 views

### 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 ...
120 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 ...
155 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 ...
411 views

### 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 ...
1k views

### 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 ...
171 views

### 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, ...
377 views

### 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 ...
42 views

### 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 ...
474 views

### 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 ...
197 views

### 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 ...
12k views

### 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 ...
341 views

### 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 ...
351 views

### 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 ...
467 views

### Is there any 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 & answers on Stack Overflow....
205 views

### Finding metrics for development time in different languages [closed]

I'm trying to determine if a language I'm investigating (Groovy) is better for developing enterprise applications than our current language (Java). Specifically I'm trying to figure out if it will ...
127 views

### comparison of an unsigned variable to 0

When I execute the following loop : unsigned m; for( m = 10; m >= 0; --m ){ printf("%d\n",m); } the loop doesn't stop at m==0, it keeps executing interminably, so I thought that ...
472 views

### Comparing two software versions in C#

I´m working on a mod update checker for minecraft, but there is a big problem: The modders and online database that I´m using for update checks has no standard software versions e.g.: Local: rv0-...
58 views

### How to develop a product compare page

I want to develop a product comparison page, where a user can compare 2 or 3 products. I was thinking about a 3 column list displaying every specification. But I want to highlight the differences. I ...
52k views

### How can Swift be so much faster than Objective-C in these comparisons?

Apple launched its new programming language Swift at WWDC14. In the presentation, they made some performance comparisons between Objective-C and Python. The following is a picture of one of their ...
360 views

### How to (or should I) have one assert per test with object comparisons? [duplicate]

I've recently read The Art of Unit Testing by Roy Osherove which I found very useful for helping me establish how to define a good unit test. One key aspect of the guidelines Roy puts forward are to ...
171 views

### How to choose between different open-source libraries? [closed]

Recently, I found multiple GitHub repositories that would allow me to perform the same task. (In my case, assess the readability of text strings.) It made me wonder, what are the best practices for ...
1k views

### Why is PHP's method of comparing different types bad?

I'm working on designing a new programming language and trying to decide how I will do variable comparisons. Along with many different types of languages, I've used PHP for years and personally had ...
3k views

### Shallow or deep equal, which one is idiomatic in Java?

I have a domain model in which I use a few aggregation relations, i.e. an object of class A contains zero or more objects of class B. I use Java for the implementation and I represent such an ...
486 views

### Which is the better: a <= b or a < b+1 [closed]

For loops are usually inclusice, exclusive, meaning that you start at the bottom, and stops when you reach, but don't to the top. In Python: for i in range(0,a): print(i) would print 0 through ...
203 views

### Importance of diffing and merging for design specifications documentation

The context of this question is choosing tools for writing design specifications for software projects. These documents will be written and maintained by architects and developers, I'm not talking ...
618 views

### Trying to understand the 2N lnN compares for quicksort

I was going through the analysis of quicksort in Sedgewick's Algorithms book. He creates the following recurrence relation for number of compares in quicksort while sorting an array of N distinct ...
267 views

### Best practice to sort then reverse, or write “backwards” comparator?

I wrote a comparator for a custom class of mine and when I ran my code I realised the output of my list of these objects was in the reverse order as to what I wanted. It was "ascending" as opposed to "...
2k views

### Tricky compareTo, inheritance, easy to extend - Java

Let's say we have 4 classes A, B, C, D where: A is a superclass of both B and C and C is a superclass of D. I suppose, in a diagram, it should look like this: A / \ B C \ D ...
3k views

### How do you find the first common element in two arrays

How do you find the first common element in two arrays? My attempt: I looped through each at the same time and add the current value to a separate set for each of the lists. Also, check if the ...
1k views

### Scala as a language for Generic Programming

In the paper “An Extended Comparative Study of Language Support for Generic Programming” by Garcia et al. an interesting comparison of programming languages features for generic programming is given: ...
770 views

### Are Scrum and XP comparable things or are they used for different things

Are Scrum and XP comparable things or are they used for different things? what is the main features of each of them? how do they overlap? I've been reading about both XP and Scrum over the past weeks ...
261 views

### I need some help creating a non-binary tree (or some other data structure that will better solve my problem)

I have about ten lists of numbers and some strings. Each list has about <= 30K lines. Each line on a list has a distinct number. I need to build an efficient way of finding all the lines in each ...
1k views

### How representative is Ohloh? [closed]

My colleague recently pointed me to Ohloh, a website providing statistics on FOSS based on versioning repositories. It's quite a fun procrastination tool, e.g. to compare programming languages by ...
2k views

### When to use identity comparison instead of equals?

I wonder why would anybody want to use identity comparison for fields in equals, like here (Java syntax): class C { private A a; public boolean equals(Object other) { // standard ...
528 views

### What do you call “X <= \$foo <= Y” comparison?

While writing a Perl statement like if ( \$foo >= X && \$foo <= Y ) yet again, I wondered why many programming languages do not support the more comfortable form if ( X <= \$foo <= Y )...
550 views

### Efficient way to compare scene-graph trees

I'm designing a scene graph system, where it is required to compare two trees. The trees are populated with individual objects, each with varied number of children; and they have a root. Eg: Parent: ...
204 views

### Custom graph comparison?

I'm trying to compare two graphs using hash value ( i.e, at the time of comparison, try to avoid traversing the graph ) Is there a way to make a function such that the hash values compared can also ...