Comparison operators, as their name implies, allow to compare two values and usually return Boolean value (true or false).
Questions tagged [comparison-operators]
658 questions
52
votes
2 answers
Why is operator!= removed in C++20 for many standard library types?
According to cppreference, std::type_info::operator!= gets removed with C++20, however, std::type_info::operator== apparently remains.
What's the reasoning behind? I might agree on comparing for inequality being meaningless, but then comparing for…
Aconcagua
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votes
7 answers
Numeric comparison difficulty in R
I'm trying to compare two numbers in R as a part of a if-statement condition:
(a-b) >= 0.5
In this particular instance, a = 0.58 and b = 0.08... and yet (a-b) >= 0.5 is false. I'm aware of the dangers of using == for exact number comparisons, and…
Matt Parker
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49
votes
7 answers
Why does new String('hello') === new String('hello') evaluate to False?
Why does the following statement return false in JavaScript?
new String('hello') === new String('hello')
santosh kore
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49
votes
3 answers
Using comparison operators in SELECT clause of T-SQL query
How to select a result of comparison operator as a field with type BIT?
How it does work in C#:
bool isGreater = FieldA > FieldB;
How it doesn't work in T-SQL:
SELECT (FieldA > FieldB) AS BIT FROM t
How to write such task properly?
abatishchev
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45
votes
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What does `!!~` mean in javascript?
Possible Duplicate:
What does tilde (~) preceding jQuery object do?
I found a strange !!~ in the code when reading: https://github.com/LearnBoost/mongoose/blob/master/lib/document.js#L678
Document.prototype.isModified = function (path) {
return…
Freewind
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43
votes
3 answers
C# Type Comparison: Type.Equals vs operator ==
ReSharper suggests that the following be changed from:
Type foo = typeof( Foo );
Type bar = typeof( Bar );
if( foo.Equals( bar ) ) { ... }
To:
if( foo == bar ) { ... }
operator ==
// Summary:
// Indicates whether two System.Type objects are…
Metro Smurf
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43
votes
2 answers
What are the breaking changes caused by rewritten comparison operators?
There are some new rules about rewritten comparison operators in C++20, and I'm trying to understand how they work. I've run into the following program:
struct B {};
struct A
{
bool operator==(B const&); // #1
};
bool operator==(B const&, A…
cigien
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40
votes
3 answers
Why is 'True == not False' a syntax error in Python?
Comparing boolean values with == works in Python. But when I apply the boolean not operator, the result is a syntax error:
Python 2.7 (r27:82500, Sep 16 2010, 18:02:00)
[GCC 4.5.1 20100907 (Red Hat 4.5.1-3)] on linux2
Type "help", "copyright",…
Tim Martin
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40
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11 answers
C# Nullable Equality Operations, Why does null <= null resolve as false?
Why is it that in .NET
null >= null
resolves as false, but
null == null
resolves as true?
In other words, why isn't null >= null equivalent to null > null || null == null?
Does anyone have the official answer?
Ben
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votes
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JavaScript equality transitivity is weird
I've been reading Douglas Crockford's JavaScript: The Good Parts, and I came across this weird example that doesn't make sense to me:
'' == '0' // false
0 == '' // true
0 == '0' // true
false == undefined //…
Hristo
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votes
3 answers
Is JavaScript's double equals (==) always symmetric?
There are many cases in which JavaScript's type-coercing equality operator is not transitive. For example, see "JavaScript equality transitivity is weird."
However, are there any cases in which == isn't symmetric? That is, where a == b is true and b…
Trevor Burnham
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32
votes
4 answers
"is not required" == undefined behavior?
My question is mainly about terminology and how to interpret the standard.
[expr.rel]#4:
The result of comparing unequal pointers to objects is defined in terms of a partial order consistent with the following rules:
(4.1) If two pointers point to…
463035818_is_not_a_number
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32
votes
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Is comparison of const_iterator with iterator well-defined?
Consider the following code:
#include
#include
int main()
{
std::vector vec{1,2,3,5};
for(auto it=vec.cbegin();it!=vec.cend();++it)
{
std::cout << *it;
// A typo: end instead of cend
…
Ruslan
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Python's in (__contains__) operator returns a bool whose value is neither True nor False
As expected, 1 is not contained by the empty tuple
>>> 1 in ()
False
but the False value returned is not equal to False
>>> 1 in () == False
False
Looking at it another way, the in operator returns a bool which is neither True nor False:
>>>…
user2949478
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votes
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JavaScript - === vs == operators performance
A few weeks ago, I have read this thread Is < faster than <=? about comparison operators in C. It was said that there is no difference in the performance between < and <= as they are interpreted as same/similar machine commands.
At the same time, in…
gotqn
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