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134
votes
7answers
160k views

When do you use float and when do you use double

Frequently in my programming experience I need to make a decision whether I should use float or double for my real numbers. Sometimes I go for float, sometimes I go for double, but really this feels ...
79
votes
6answers
13k views

Why are floats still part of the Java language when doubles are mostly recommended instead?

In every place I've looked, it says that double is superior to float in almost every way. float has been made obsolete by double in Java, so why is it still used? I program a lot with Libgdx, and ...
53
votes
11answers
14k views

Get 100 highest numbers from an infinite list

One of my friend was asked this interview question - "There is a constant flow of numbers coming in from some infinite list of numbers out of which you need to maintain a datastructure as to ...
40
votes
3answers
5k views

Are there numbers that are not representable in base 10 but can be represented in base 2?

C# has the decimal type which is used for numbers that needs exact representation in base 10. For instance, 0.1 cannot be represented in base 2 (e.g. float and double) and will always be an ...
40
votes
2answers
4k views

Why do some languages round to the nearest EVEN integer?

Programming languages like Scheme (R5RS) and Python (see this Question) round towards the nearest even integer when value is exactly between the surrounding integers. What is the reasoning behind ...
37
votes
3answers
37k views

Why is 2^16 a “special” number? [closed]

OK, I feel stupid asking this - but in Jeff's article: Getting the Interview Phone Screen Right and originally stated in the 5 essential phone screen questions: They shouldn't stare blankly at you ...
36
votes
1answer
2k views

Where does paypal's 92233720368547800 number come from? [closed]

There has been a story in the news about a man whose Paypal account was accidentally credited with $92,233,720,368,547,800. Where does this number come from? What sort of programming bug is likely to ...
22
votes
4answers
2k views

Has Little Endian won?

When teaching recently about the Big vs. Little Endian battle, a student asked whether it had been settled, and I realized I didn't know. Looking at the Wikipedia article, it seems that the most ...
20
votes
6answers
7k views

Why don't computers store decimal numbers as a second whole number?

Computers have trouble storing fractional numbers where the denominator is something other than a solution to 2^x. This is because the first digit after the decimal is worth 1/2, the second 1/4 (or 1/...
15
votes
4answers
5k views

How can I properly compare double values for equality in a unit test?

I recently designed a time series module where my time series is essentially a SortedDictionnary<DateTime, double>. Now I would like to create unit tests to make sure that this module is always ...
14
votes
2answers
2k views

Why '42' is the preferred number when indicating something random?

I have seen this on the SO on many times. Whenever a question is vague and the question is asking some magical answer somebody or the other leaves a comment saying answer is 42. Even a book I am ...
14
votes
4answers
1k views

How to identify unstable floating point computations?

In numerics, it is very important to be able to identify unstable schemes and to improve their stability. How to identify unstable floating point computations? I am working on a very complex ...
12
votes
8answers
4k views

Find a “hole” in a list of numbers

What is the fastest way to find the first (smallest) integer that doesn't exist in a given list of unsorted integers (and that is greater than the list's smallest value)? My primitive approach is ...
12
votes
6answers
2k views

any document which says exactly what range of numbers are .NET BigIntegers designed for?

I'm playing around with the .NET BigInteger and basically I'm wondering what number --an estimated answer would be fine-- is the point of deviation of the curve of (the graph of (increase of time ...
10
votes
3answers
440 views

Why is the minimum value of ints, doubles, etc 1 farther from zero than the positive value?

I know it has something to do with 2's complement and adding 1, but I don't really get how you can encode one more number with the same amount of bits when it comes to negative numbers.
9
votes
8answers
2k views

A good schema to represent integer numbers from 0 to infinity, assuming you have infinite linear binary storage?

I would like a schema to represent integer numbers starting with 0, without any limit (assuming access to infinite linear storage). Here's a schema that can represent numbers from 0 to 255: Use the ...
9
votes
7answers
6k views

Why are there so many numeric types (bit, int, float, double, long)?

I've learned PHP, Java, and C. Now I'm curious as to why there are so many types of numerical data types like bit, int, float, double, and long. Why not make only one type for numericals? Is there ...
8
votes
6answers
19k views

How do random number generators work?

I was just pondering about php rand() function, and thinking about how I could remake it, and I came up completely stupified. How the heck do random number generators work?
6
votes
3answers
18k views

Is there something special about the number 65535?

2¹⁶-1 & 2⁵ = 2⁵ (or? obviously ?) A developer asked me today what is bitwise 65535 & 32 i.e. 2¹⁶-1 & 2⁵ = ? I thought at first spontaneously 32 but it seemed to easy whereupon I thought ...
5
votes
2answers
8k views

binary representation in Python and keeping leading zeros

I wanted to use the base64 Python library to encode a sequence of binary digits into base 64. Would it be possible to do it without converting to a string? If not, what is the best way to do it, ...
4
votes
3answers
1k views

When is a number a magic number?

Over the last couple of months I have been diving into coding standard IfSQ. As a part of this IfSQ standard, a rule is to not use Magic Numbers. While I don't have a problem with building this rule ...
4
votes
5answers
2k views

sets of numbers that sum to a certain number?

I was asked this in an interview, and I'm not sure what the answer is or how to approach the problem. Find a pair of numbers that sum up to zero (or any other number), then find three (and then ...
3
votes
2answers
170 views

How widespread is the use of arabic numerals in Japanese and Chinese?

I'm localising a times-table app aimed at children. I understand that the Japanese and Chinese languages have a variety of ways to represent numbers. I also have read that, particularly with Japanese, ...
3
votes
2answers
161 views

Trivially Sortable Encoding for Arbitrary-Precision Decimals

I'm looking for a reasonably(*) space-efficient way to encode arbitrary-precision decimals (e.g. BigDecimal), such that when sorting the bit-pattern of the encodings lexicographically, the numbers ...
2
votes
2answers
7k views

complex numbers in programming?

Are complex numbers used in programming? If they are what is their significance? What IDEs and languages use them? And would it be recommended to learn how to implement them for a programming job (if ...
2
votes
4answers
3k views

Understanding binary numbers in terms of real world objects [closed]

When I represent a number in the decimal system, I have an intuitive knowledge of what it amounts to. For example take the number '10': I understand that it means 10 apples or 10 people... i.e I can ...
2
votes
3answers
2k views

In programming light, what is special about the number 1223? [closed]

Just came across this post on reddit, where someone was charged $1,223 for a "FREE STEAK SALAD". I was trying to figure out 'Why 1223?' thinking that this might be a programming error somewhere. ...
2
votes
3answers
6k views

What is the time complexity of the algorithm to check if a number is prime?

What is the time complexity of the algorithm to check if a number is prime? This is the algorithm : bool isPrime (int number) { if (number < 2) return false; if (number == 2) return ...
2
votes
2answers
241 views

Which numeral systems are useful in computer science?

I am wondering which numeral system different programmers are using, or would use if their language has support for them. As an example, in C++ we can use: Octal by prefixing with 0 (e.g. 0377) ...
2
votes
1answer
39 views

Exclusive upper bound in random number range

Why do languages' random number generators tend to return a value exclusive of the upper bound of the range? For example, an implicit range - JavaScript's random() method "Return a random number ...
2
votes
3answers
315 views

What implementation do you use when dealing with operators in .Net?

My question is in a sense a follow up of this post on Time Series in .Net. Ideally, you would like to expand the basic TimeSeries<T> class by something like NumericTimeSeries<T>, where ...
2
votes
1answer
393 views

Filling array with numbers from given range so that sum of adjacent numbers is square number

Problem: Fill all the cells using distinct numbers from <1,25> set, so that sum of two adjacent cells is a square number. (source: http://grymat.im.pwr.wroc.pl/etap1/zad1etp1213.pdf; numbers 20 ...
1
vote
3answers
198 views

Does printing out numbers involve converting the numbers into characters?

In programming languages, when numbers (either integer, or real) are printed out, are they firstly converted to the codes of the readable characters that are meant to represent the numbers, and then ...
1
vote
3answers
397 views

Is there any programming language(s) which has mathematical number types? [closed]

I may not have worded the title correctly. Is there any programming language(s) which deals with natural mathematical number types rather than the typical data types we see like Int32, Int64, Float, ...
1
vote
3answers
130 views

Generate random numbers with certain spikes? [duplicate]

I am trying to generate random numbers to simulate steering wheel angles and velocities of a car. So for steering wheels the random numbers could go like 1,2,4,6,4,3,40,0. I can generate random ...
1
vote
1answer
203 views

Why are floats called “real numbers” in some languages?

Some programing languages, notably Pascal, have a type of numbers called "real". However, mathematically speaking, these types aren't real. For them to be "real", these types have to be able to ...
1
vote
1answer
940 views

Sum of divisors of numbers of the range ~ 10^6

I was trying to find the sum of divisors of numbers upto 106. The test cases are like of the order of 105. I have done some pre processing like int divisors(int num) { int sum=0; for(int i=1;...
1
vote
1answer
44 views

Should arbitrary numbers be stored as strings in a database?

I'm using Google as a login system for my latest project. So, my users table has a column named googleid, which stores Google's unique user id, which is a number, with a few dozen digits. For example, ...
1
vote
2answers
85 views

How to implement rounding in an all-purpose stack language using different types?

Disclaimer: If you are not terribly interested in numerics and mathematical processes, this is most likely nothing for you. I am currently a bit stuck in a development process of a private project I ...
0
votes
4answers
418 views

Why is it an issue that it takes 2 digits to represent the number 10 in decimal? [closed]

So we use hexadecimal which has the advantage of going up to 15 in single digits A-F, but why is it an issue that it takes 2 digits to represent the number 10 in decimal? I was reading up about ...
0
votes
5answers
579 views

Is String processing more complex than number processing in programming languages?

I feel that string processing is always more complex than Numbers or mathematical processing. Are our programming languages are designed this way that mathematical operations are pretty much straight ...
0
votes
2answers
171 views

What is the best type to represent a number in java and why? [closed]

I am developing a dynamically typed, interpreted programming language, which is interpreted by a runtime written in Java. As Java is statically typed, I need to define how the numbers used in the ...
0
votes
3answers
619 views

What is more efficient, a single square root or multiple divisions?

Say I make a program that calculates all possible (integral) factors of a certain number that has been input. Is it theoretically more efficient to check with all integers up to the square root of ...
0
votes
1answer
665 views

Algorithm for base-conversion in C?

I put in this code which does what it's supposed to do, but perhaps there is a better or more general approach? I'm converting a 4-digit base 10 number e.g. "11" to base 16 e.g. "17" (which gets ...
0
votes
1answer
445 views

How many ALU additions are needed to add three numbers?

Please give reasons for your answer. As I found, two additions are needed. This is because every number to be add needs to changed to binary. Then addition is done between two binary numbers where ...
0
votes
1answer
186 views

Representing the hierarchy of groups of numbers using type inheritance

I've run into an interesting conundrum while coding my own implementations for the basic sets of mathematical numbers (Natural, Integer, Rational, Irrational, Real, Complex). I'm doing this mostly for ...
0
votes
2answers
260 views

Algorithm for picking reasonable min/max vals given a single value

I am making a simplistic in-browser IDE for some very domain-specific coding. Because I like Bret Victor's thoughts on Learnable Programming so much I thought I'd throw in some draggable numbers ala ...
0
votes
1answer
78 views

Combine sequences of numbers with “variable bitlengths” into short unique strings

It is not unlikely that what I want to do is not possible, but it doesn't hurt to ask. Imagine a set of lists, each containing positive integers (in my case, a list always consists of four integers, ...
-1
votes
3answers
618 views

Generate unique integer from two integers with algorithm

I am currently trying to come up with an algoritm which would take at least two numbers (say user IDs) and then come up with an unique number which is generated based on these two numbers. Each ...
-2
votes
1answer
107 views

Find missing number in sequence in string [closed]

I have a string that contains numbers in sequence. There are no delimiters between numbers. I have to find missing number in that sequence. For example: 176517661768 is missing the number: 1767 ...