Improve writeup.

doc/src/language/logic.md

@@ -65,42 +65,3 @@ a() | b();              // both a() and b() are evaluated
 
 a() & b();              // both a() and b() are evaluated
 ```
-
-Compound Assignment Operators
-----------------------------
-
-```rust
-let number = 9;
-
-number += 8;            // number = number + 8
-
-number -= 7;            // number = number - 7
-
-number *= 6;            // number = number * 6
-
-number /= 5;            // number = number / 5
-
-number %= 4;            // number = number % 4
-
-number ~= 3;            // number = number ~ 3
-
-number <<= 2;           // number = number << 2
-
-number >>= 1;           // number = number >> 1
-
-number &= 0x00ff;       // number = number & 0x00ff;
-
-number |= 0x00ff;       // number = number | 0x00ff;
-
-number ^= 0x00ff;       // number = number ^ 0x00ff;
-```
-
-The `+=` operator can also be used to build [strings]:
-
-```rust
-let my_str = "abc";
-my_str += "ABC";
-my_str += 12345;
-
-my_str == "abcABC12345"
-```