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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--; 3: a--;
4: --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 ### 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. 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.