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added example for incrementation (#23908)

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kzellers
2018-12-01 19:02:30 -08:00
committed by Manish Giri
parent 78c6e30439
commit 97f80c715c
1 changed files with 9 additions and 1 deletions
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10
guide/english/c/more-math/index.md
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@ -25,7 +25,15 @@ There are a lot of situations where you want to take a number and either go up o
3: a--;
4: --a;
```
Both the examples at 1 and 2 will increase the value of a by one. Both of the examples at 3 and 4 will decrease the value of a by one. However, 1 does not do quite the same thing as 2, and 3 does not do quite the same thing as 4. Pre-fix operators are called this because the operation is a prefix (2 and 4 are our prefix operators). This acts slightly differently from our post-fix operators at 1 and 3. Pre-fix operators perform the operation, then return the value. Post-fix operators return the value, then perform the incrementation.
Both the examples at 1 and 2 will increase the value of a by one. Both of the examples at 3 and 4 will decrease the value of a by one. However, 1 does not do quite the same thing as 2, and 3 does not do quite the same thing as 4. Pre-fix operators are called this because the operation is a prefix (2 and 4 are our prefix operators). This acts slightly differently from our post-fix operators at 1 and 3. Pre-fix operators perform the operation, then return the value. Post-fix operators return the value, then perform the incrementation. You can see the effects of this difference here:
```C
int a = 1;
int b = ++a; // b = 2, a = 2
int c = 1;
int d = c++; //c = 2, d = 1
```
### Unary plus and minus
In the normal math you're used to, you use a '-' in front of a number or variable, and that makes the number or variable negative. If the number or variable is already negative, it becomes positive.