I want to create a non-thread-safe chunk of code for experimentation, and those are the functions that 2 threads are going to call.

    c = 0
    
    def increment():
      c += 1
    
    def decrement():
      c -= 1

Is this code thread safe?

If not, may I understand why it is not thread safe, and what kind of statements usually lead to non-thread-safe operations.

If it is thread-safe, how can I make it explicitly non-thread-safe?

Is the += operator thread-safe in Python?

```
int i = 3;
int j = (i)++;
```
vs 
```
int i = 3;
int j = i ++;
```
Is there a difference between how the above two cases are evaluated?

Is the first case equivalent to incrementing an rvalue or is it undefined behaviour?


Difference between i++ and (i)++ in C

How do I use pre-increment/decrement operators (`++`, `--`), just like in C++?

Why does `++count` run, but not change the value of the variable?

Behaviour of increment and decrement operators in Python

I&#39;ve always laughed to myself when I&#39;ve looked back at my VB6 days and thought, &quot;What modern language doesn&#39;t allow incrementing with double plus signs?&quot;:

```
number++
```

To my surprise, I can&#39;t find anything about this in the Python docs. Must I really subject myself to `number = number + 1`? Don&#39;t people use the `++` / `--` notation?

Python integer incrementing with ++

    #include &lt;stdio.h&gt;

    int main(void)
    {
       int i = 0;
       i = i++ + ++i;
       printf(&quot;%d\n&quot;, i); // 3
    
       i = 1;
       i = (i++);
       printf(&quot;%d\n&quot;, i); // 2 Should be 1, no ?
    
       volatile int u = 0;
       u = u++ + ++u;
       printf(&quot;%d\n&quot;, u); // 1
    
       u = 1;
       u = (u++);
       printf(&quot;%d\n&quot;, u); // 2 Should also be one, no ?
    
       register int v = 0;
       v = v++ + ++v;
       printf(&quot;%d\n&quot;, v); // 3 (Should be the same as u ?)

       int w = 0;
       printf(&quot;%d %d\n&quot;, ++w, w); // shouldn&#39;t this print 1 1

       int x[2] = { 5, 8 }, y = 0;
       x[y] = y ++;
       printf(&quot;%d %d\n&quot;, x[0], x[1]); // shouldn&#39;t this print 0 8? or 5 0?
    }

    

Why are these constructs using pre and post-increment undefined behavior?

Does R have a concept of `+=` (plus equals) or `++` (plus plus) as c++/c#/others do?

R:  += (plus equals) and ++ (plus plus) equivalent from c++/c#/java, etc.?

In JavaScript you can use `++` operator before (*pre-increment*) or after the variable name (*post-increment*).  What, if any, are the differences between these ways of incrementing a variable?

++someVariable vs. someVariable++ in JavaScript

With MySQL, if I have a field, of say logins, how would I go about updating that field by 1 within a sql command?

I&#39;m trying to create an INSERT query, that creates firstName, lastName and logins.  However if the combination of firstName and lastName already exists, increment the logins by 1.

so the table might look like this..

    firstName----|----lastName----|----logins
    
    John               Jones             1
    Steve              Smith             3

I&#39;m after a command that when run, would either insert a new person (i.e. Tom Rogers) or increment logins if John Jones was the name used..



Increment a database field by 1

So I&#39;m iterating over a range like so:

    (1..100).each do |n|
        # n = 1
        # n = 2
        # n = 3
        # n = 4
        # n = 5
    end

But what I&#39;d like to do is iterate by 10&#39;s.

So in stead of increasing `n` by 1, the next `n` would actually be 10, then 20, 30, etc etc.


Ruby: How to iterate over a range, but in set increments?

Are there other ways to increment a `for` loop in Javascript besides `i++` and `++i`? For example, I want to increment by 3 instead of one. 

    for (var i = 0; i &lt; myVar.length; i+3) {
       //every three
    }

Can a for loop increment/decrement by more than one?

I am looking at Xcode 7.3 notes and I notice this issue.

&gt; The ++ and -- operators have been deprecated

Could some one explain why it is deprecated? And am I right that in new version of Xcode now you going to use instead of `++` this `x += 1`;

Example:

    for var index = 0; index &lt; 3; index += 1 {
        print(&quot;index is \(index)&quot;)
    }

[![Screenshot for warning][1]][1]


  [1]: http://i.stack.imgur.com/3DUjN.png

The &quot;++&quot; and &quot;--&quot; operators have been deprecated Xcode 7.3

Recently I have come across this problem which I am unable to understand by myself.

What do these three Expressions **REALLY** mean?

    *ptr++
    *++ptr
    ++*ptr
I have tried Ritchie. But unfortunately was unable to follow what he told about these 3 operations.

I know they are all performed to increment the pointer/the value pointed to. I can also guess there may be a lot of things about precedence and order of evaluation. Like one increments the pointer first then fetches the content of that pointer, one simply fetches the content and then increments the pointer etc etc. As you can see, I don&#39;t have a clear understanding about their **actual** operations, which i would like to clear as soon as possible. But I am truly lost when I get a chance to apply them in programs. For example:

    int main()
    {
        char *p = &quot;Hello&quot;;
        while(*p++)
             printf(&quot;%c&quot;,*p);
        return 0;
    }

gives me this output:

    ello

But my expectation was that it would print `Hello` .
One final request -- Please give me examples for how each expression works in a given code snippet. As most of the time only a mere paragraph of theory gets flown over my head.


Pointer expressions: *ptr++, *++ptr and ++*ptr

I&#39;m a little new to postgres. I want to take a value (which is an integer) in a field in a postgres table and increment it by one. For example if the table &#39;totals&#39; had 2 columns, &#39;name&#39; and &#39;total&#39;, and Bill had a total of 203, what would be the SQL statement I&#39;d use in order to move Bill&#39;s total to 204?

Increment a value in Postgres

Is there a difference between ++x and x++ in java?

Is there a difference between x++ and ++x in java?

Does anyone know of a Javascript library (e.g. underscore, jQuery, MooTools, etc.) that offers a method of incrementing a letter?

I would like to be able to do something like:

    &quot;a&quot;++; // would return &quot;b&quot;

What is a method that can be used to increment letters?

After researching, I read that the increment operator requires the operand to have a modifiable data object: https://en.wikipedia.org/wiki/Increment_and_decrement_operators.

From this I guess that it gives compilation error because `(a+b)` is a temporary integer and so is not modifiable.

Is this understanding correct? This was my first time trying to research a problem so if there was something I should have looked for please advise.


Why does c = ++(a+b) give compilation error?

I&#39;m new to Python, coming from Java and C. How can I increment a char? In Java or C, chars and ints are practically interchangeable, and in certain loops, it&#39;s very useful to me to be able to do increment chars, and index arrays by chars. 

How can I do this in Python? It&#39;s bad enough not having a traditional for(;;) looper - is there any way I can achieve what I want to achieve without having to rethink my entire strategy?

How can I increment a char?

Today while writing some Visual C++ code I have come across something which has surprised me. It seems C++ supports ++ (increment) for bool, but not -- (decrement). It this just a random decision, or there is some reason behind this?

This compiles:

    static HMODULE hMod = NULL;
    static bool once = false;
    if (!once++)
        hMod = LoadLibrary(&quot;xxx&quot;);

This does not:

    static HMODULE hMod = NULL;
    static bool once = true;
    if (once--)
        hMod = LoadLibrary(&quot;xxx&quot;);

bool operator ++ and --

In programming, particularly in Java, what is the difference between:

    int var = 0;
    var++;

and 

    int var = 0;
    ++var;

What repercussions would this have on a for loop?

e.g.

    for (int i = 0; i &lt; 10; i++) {}
    
    for (int i = 0; i &lt; 10; ++i) {}


The difference between ++Var and Var++

I have the following code:

    public class Tests {
    	public static void main(String[] args) throws Exception {
    		int x = 0;
    		while(x&lt;3) {
    			x = x++;
    			System.out.println(x);
    		}
    	}
    }

We know he should have writen just `x++` or `x=x+1`, but on `x = x++` it should first attribute `x` to itself, and later increment it. Why does `x` continue with `0` as value?

**--update**

Here&#39;s the bytecode:

    public class Tests extends java.lang.Object{
    public Tests();
      Code:
       0:	aload_0
       1:	invokespecial	#1; //Method java/lang/Object.&quot;&lt;init&gt;&quot;:()V
       4:	return
    
    public static void main(java.lang.String[])   throws java.lang.Exception;
      Code:
       0:	iconst_0
       1:	istore_1
       2:	iload_1
       3:	iconst_3
       4:	if_icmpge	22
       7:	iload_1
       8:	iinc	1, 1
       11:	istore_1
       12:	getstatic	#2; //Field java/lang/System.out:Ljava/io/PrintStream;
       15:	iload_1
       16:	invokevirtual	#3; //Method java/io/PrintStream.println:(I)V
       19:	goto	2
       22:	return
    
    }

I&#39;ll read about the [instructions][1] to try to understand...


  [1]: http://en.wikipedia.org/wiki/Java_bytecode_instruction_listings

Why does this go into an infinite loop?

I have an `int` pointer (i.e., `int *count`) that I want to increment the integer being pointed at by using the `++` operator. I thought I would call:

    *count++;

However, I am getting a build warning *&quot;expression result unused&quot;*. I can: call

    *count += 1;

But, I would like to know how to use the `++` operator as well. Any ideas?

increment value of int being pointed to by pointer

I have been fooling around with some code and saw something that I don&#39;t understand the &quot;why&quot; of.

    int i = 6;
    int j;

    int *ptr = &amp;i;
    int *ptr1 = &amp;j

    j = i++;

    //now j == 6 and i == 7. Straightforward.

What if you put the operator on the left side of the equals sign?

    ++ptr = ptr1;

is equivalent to

    (ptr = ptr + 1) = ptr1; 

whereas

    ptr++ = ptr1;

is equivalent to

    ptr = ptr + 1 = ptr1;


The postfix runs a compilation error and I get it. You&#39;ve got a constant &quot;ptr + 1&quot; on the left side of an assignment operator. Fair enough. 

The prefix one compiles and WORKS in C++. Yes, I understand it&#39;s messy and you&#39;re dealing with unallocated memory, but it works and compiles. In C this does not compile, returning the same error as the postfix &quot;lvalue required as left operand of assignment&quot;. This happens no matter how it&#39;s written, expanded out with two &quot;=&quot; operators or with the &quot;++ptr&quot; syntax.

What is the difference between how C handles such an assignment and how C++ handles it?

The difference between C and C++ regarding the ++ operator

In a loop in C++, I usually encounter situations to use `++` or `+=1`, but I can&#39;t tell their difference. For instance, if I have an integer

    int num = 0;

and then in a loop I do:

    num ++;

or
 
    num += 1;

they both increase the value of `num`, but what is their difference? I doubt `num++` could work faster than `num+=1`, but how? Is this difference subtle enough to be ignored? 

What is the difference between &quot;++&quot; and &quot;+= 1 &quot; operators?

Is there any reason for Scala not support the ++ operator to increment primitive types by default?
For example, you can not write:

    var i=0
    i++

Thanks

Increment (++) operator in Scala

Here&#39;s a simple console application code, which returns a result I do not understand completely.

Try to think whether it outputs 0, 1 or 2 in console:

    using System;
    
    namespace ConsoleApplication
    {
        class Program
        {
            static void Main()
            {
                int i = 0;
                i += Increment(ref i);
    
                Console.WriteLine(i);
                Console.ReadLine();
            }
    
            static private int Increment(ref int i)
            {
                return i++;
            }
        }
    }


The answer is 0.

What I don&#39;t understand is why post increment `i++`, from the `Increment` method, which is executed on a `ref` (not on a copy of the passed variable) does increment the variable, but it just gets ignored later.

What I mean is in this video:

[![][1]][2]

Can somebody explain this example and why during debug I see that value is incremented to 1, but then it goes back to 0?


  [1]: https://i.stack.imgur.com/o0mWk.gif
  [2]: https://www.screencast.com/t/DkBvGmJv

All Increment Solutions on Gang of Coders

Total of 25 Increment Solutions