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54
votes
11answers
18k views

Why is String immutable in Java?

I couldn't understand the reason of it. I always use String class like other developers, but when I modify the value of it, new instance of String created. What might be the reason of immutability ...
48
votes
11answers
59k views

SQL: empty string vs NULL value

I know this subject is a bit controversial and there are a lot of various articles/opinions floating around the internet. Unfortunatelly, most of them assume the person doesn't know what the ...
44
votes
3answers
2k views

Etymology of “String”

So it's obvious that a string of things is a sequence of things, and so a sequence of characters/bytes/etc. might as well be called a string. But who first called them strings? And when? And in what ...
38
votes
6answers
7k views

Hardcoding strings that will never change

So, in my efforts to write a program to conjugate verbs (algorithmically, not through a dataset) for French, I've come across a slight problem. The algorithm to conjugate the verbs is actually fairly ...
21
votes
5answers
2k views

Why are strings so slow?

Ever since my very first programming class in high school, I've been hearing that string operations are slower — i.e. more costly — than the mythical "average operation." Why makes them so ...
20
votes
5answers
94k views

Is initializing a char[] with a string literal bad practice?

I was reading a thread titled "strlen vs sizeof" on CodeGuru, and one of the replies states that "it's anyways [sic] bad practice to initialie [sic] a char array with a string literal." Is this ...
18
votes
2answers
7k views

Why does Java use UTF-16 for internal string representation?

I would imagine the reason was fast, array like access to the character at index, but some characters won't fit into 16 bits, so it wouldn't work... So if you have to handle special cases anyways, ...
16
votes
3answers
596 views

Is it possible to write a generalized string reverse function that works for all localisations and string types?

I was just watching the Jon Skeet (with Tony the Pony) presentation from Dev-Days. Although "write a string reverse function" is coding interview 101 - I'm not sure that it's actually possible to ...
15
votes
5answers
9k views

Should a string constant be defined if it's only going to be used once?

We're implementing an adapter for Jaxen (an XPath library for Java) that allows us to use XPath to access the data model of our application. This is done by implementing classes which map strings ...
14
votes
3answers
2k views

How many strings are created in memory when concatenating strings in Java?

I was asked about immutable strings in Java. I was tasked with writing a function that concatenated a number of "a"s to a string. What I wrote: public String foo(int n) { String s = ""; for ...
11
votes
2answers
572 views

Why store flags/enums in a database as strings instead of integers?

I've been browsing SQL dumps of some famous CMSes, including Drupal 7, Wordpress (some quite very old version), and some custom application based on Python. All of these dumps contained data with ...
11
votes
6answers
2k views

Is it inefficient to concatenate strings one at a time?

I recall back from my days of programming in C that when two strings are joined, the OS must allocate memory for the joined string, then the program can copy all the string text over to the new area ...
11
votes
2answers
348 views

How to select a most probable option from the list based on user text Input

I am working over a OCR Application where I need to select a option based on user text input. Ex: Available Options: ["python", "ruby", "java", "clojure", "haskell"] Input: kava Output: java Input: ...
10
votes
6answers
979 views

What are the pros and cons of having a CaseInsensitiveString type in Java?

I'm tempted to create a final class CaseInsensitiveString implements CharSequence. This would allow us to define variables and fields of this type, instead of using a regular String. We can also have ...
10
votes
2answers
10k views

Which string search algorithm is actually the fastest?

I have been stuck for some time on which is the fastest string search algorithm, heard many opinions, but in the end I'm not sure. I have heard some people saying that the fastest algorithm is ...
9
votes
4answers
754 views

How defensive should we be?

We've been running Pex over some code, and it has been showing some good things (well bad things, but showing them before it gets to production!). However, one of the nice things about Pex is that it ...
9
votes
2answers
962 views

Why are Python strings allocated on the stack?

According to this Python code visualizer, Python strings are allocated on the stack and not on the heap. Why is this? I thought they would be similar to Java where Strings are allocated on the heap.
8
votes
5answers
8k views

How can I extract words from a sentence and determine what part of speech each is? [closed]

I want to write something that takes a sentence and identifies each word it contains and defines what part of speech each word is. For example Hello World, I am a sentence would return this ...
8
votes
2answers
18k views

When should I use StringBuilder or StringBuffer?

In a production web application, my fellow programmers used StringBuffer everywhere. Now I am taking care of application development and corrections. After reading StringBuilder and StringBuffer I ...
8
votes
1answer
2k views

How does PHP internally represent strings?

UTF8? UTF16? Do strings in PHP also keep track of the encoding used? Let's look at this script for example. Say I run: $original = "शक्नोम्यत्तुम्"; What actually happens? Obviously I think ...
8
votes
1answer
4k views

Shortest Common Superstring: find shortest string that contains all given string fragments

Given some string fragments, I would like to find the shortest possible single string ("output string") that contains all the fragments. Fragments can overlap each other in the output string. ...
8
votes
1answer
376 views

Match two strings but allow for a degree of error

How can I match two strings, but at the same time allow for X number of characters to be incorrect in the match. The number of errors should be a controllable variable. While X number of characters ...
8
votes
1answer
221 views

Why are C string literals read-only?

What advantage(s) of string literals being read-only justify(-ies/-ied) the: Yet another way to shoot yourself in the foot char *foo = "bar"; foo[0] = 'd'; /* SEGFAULT */ Inability to elegantly ...
8
votes
1answer
969 views

Possible Damerau-Levenshtein improvement?

I recently implemented the Damerau-Levenshtein distance algorithm from the pseudocode on Wikipedia. I couldn't find any explanation of exactly how it works and the pseudocode uses completely ...
7
votes
3answers
4k views

What performance can we expect from std::string's c_str()? Always constant time?

I've been doing some needed optimizations lately. One thing I've been doing is changing some ostringstreams -> sprintfs. I'm sprintf'ing a bunch of std::strings to a c style array, ala char foo[500]; ...
7
votes
5answers
791 views

Should functions of a C library always expect a string's length?

I'm currently working on a library written in C. Many functions of this library expect a string as char* or const char* in their arguments. I started out with those functions always expecting the ...
7
votes
1answer
277 views

String class based on graphemes?

I'm wondering why we don't have some string classes that represent a string of Unicode grapheme clusters instead of code points or characters. It seems to me that in most applications it would be ...
7
votes
3answers
542 views

Longest subsequence without string

Does there exist a dynamic programming algorithm to find the longest subsequence in a string X that does not contain Y as substring? Just that this problem seems so similar to other DP string ...
6
votes
11answers
528 views

What should I call the process of converting an object to a string?

We are having a game of 'semantic football' in the office over this matter: I am writing a method for an object which will represent the object as a string. That string should be such that when typed ...
6
votes
3answers
190 views

number of strings, when each character must occur even times

I've been bashing my skull at this problem for some time now, and its really starting to frustrate me. The problem is: I have a set of characters, A, B, C, and D. I have to tell in how many ways a ...
6
votes
5answers
3k views

Alternate string formatting options in C++?

I'm looking at optimizing some string formatting code that's hit a lot in our code. We had been using ostringstream, and I converted the code to use sprintf (actually Microsoft's more secure ...
6
votes
5answers
1k views

Why doesn't Haskell have a 'format' function for string interpolation?

I'm trying to use Shake and I stumbled upon the following problem: there's no easy and convenient way to interpolate a string. I know about Text.Printf — it's not what I'm looking for. The ...
6
votes
1answer
536 views

Finding occurrences of a useful words and phrases in strings

I am building an app that analyzes posts by people by pulling their Tweets and Facebook posts. I need to process all the posts and find useful phrases. What I mean by useful is that, any word or ...
6
votes
2answers
1k views

Complex string matching with fuzzywuzzy

I'm attempting to write a process that matches obscure strings to a single 'master string' for further processing. I have a lot of data that looks something like this: Basketball Basket Ball Football ...
6
votes
2answers
241 views

Index independent character comparison within text blocks

I have the following task: developing a program where there is a block of sample text which should be typed by user. Any typos the user does during the test are registered. Basically, I can compare ...
5
votes
6answers
16k views

string.format with variables vs inline variables

What are the pros/cons (if any) to using string output; int i = 10; output = string.Format("the int is {0}", i); versus string output; int i = 10; output = "the int is " + i; I have always ...
5
votes
2answers
346 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 ...
5
votes
1answer
61 views

Use StringLike instead of String in Scala?

Scala has the StringLike trait. Let's say I want to create a case class Name and internally it should save the name with some characters. Should I use case class Name(name: StringLike) or case class ...
4
votes
2answers
437 views

Why do people confuse C-type strings and STL strings [closed]

The last week I saw at least three questions where people were confused about the differences between char * and std::string or made some related mistakes. Don't get me wrong, I don't have a problem ...
4
votes
3answers
482 views

What should I consider when converting from ASCII to Unicode?

For instance if I had only ASCII characters and then switched to Unicode now I have to consider special characters, and bigger strings or chars. What else along these lines should I be considering? ...
4
votes
1answer
175 views

Understanding Boyer-Moore Algorithm

Edit: I've found the original publication. It seems to me that the original does not have a l′(i). But I could be wrong because the definition of rpr(i) is so obscure to me. I'm not sure how it makes ...
4
votes
2answers
443 views

Number of strings containing a specific substring

I've seen numerous questions (and answers) concerning the number of binary strings (e.g "10010" containing some binary substring (e.g "00"). I'd like to know if there is a way to generalize this: ...
3
votes
3answers
6k views

Why does Java's String class not implement a more efficient indexOf()?

Following the below question on Stack Overflow http://stackoverflow.com/questions/5564610/fast-alernative-for-stringindexofstring-str I got to wondering why it is that java (6 at least) not use a ...
3
votes
5answers
3k views

A string is immutable, so why are they not all constants?

The string type is immutable. We can use the const keyword with strings in high level language like .NET. My understanding of 'const' means constant (it remains the same, we can't change the value). ...
3
votes
5answers
6k views

How do you compress ASCII strings into smaller bytes?

I'm working with an embedded device with a unique protocol that sends messages to other devices and I'm making an application that parses the sent packets. Each packet carries 8 bytes. The protocol is ...
3
votes
3answers
2k views

Try to find a word in the dictionary that has most letters given

I recently came across an algorithm design problem that I'd like some help with: Given some letters, for example a,e,o,g,z,k,l,j,w,n and a dictionary of words. Find a word in the dictionary that ...
3
votes
2answers
132 views

Are string characters assigned a numerical value in context of how they are assigned in a programming language?

For context I am fairly new to programming after returning back to it after programming a number of years ago... I was reading Bjarne's intro programming with C++ and was wondering if alphabetical ...
3
votes
1answer
155 views

How to fix legacy code that uses <string.h> unsafely?

We've got a bunch of legacy code, written in straight C (some of which is K&R!), which for many, many years has been compiled using Visual C 6.0 (circa 1998) on an XP machine. We realize this is ...
3
votes
3answers
247 views

Storing lots of large strings with frequent “appends” and few reads

In my current project, I need to store a very long ASCII string to each instance of a given object. This string will receive an 2 appends per minute and will not be retrieved so frequently. The ...
3
votes
2answers
6k views

Which way is more efficient for getting the space count?

I have just started reading Cracking the Coding Interview. One of the problems (specifically 1.4) after solving and then looking at the answer made me question the way it is done and decided to post ...