Assignments

Value assignments to variables use the = symbol.

let foo = 42;

bar = 123 * 456 - 789;

x[1][2].prop = do_calculation();

The left-hand-side (LHS) of an assignment statement must be a valid l-value, which must be rooted in a variable, potentially extended via indexing or properties.

Expressions that are not valid _l-values_ cannot be assigned to.

```rust
x = 42;                 // variable is an l-value

x[1][2][3] = 42         // variable indexing is an l-value

x.prop1.prop2 = 42;     // variable property is an l-value

foo(x) = 42;            // syntax error: function call is not an l-value

x.foo() = 42;           // syntax error: method call is not an l-value

(x + y) = 42;           // syntax error: binary expression is not an l-value
```

Compound Assignments

Compound assignments are assignments with a [binary operator][operators] attached.

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 Flexible +=

The the + and += operators are often overloaded to perform build-up operations for different data types.

Build strings

let my_str = "abc";

my_str += "ABC";
my_str += 12345;

my_str == "abcABC12345"

Concatenate arrays

let my_array = [1, 2, 3];

my_array += [4, 5];

my_array == [1, 2, 3, 4, 5];

Concatenate BLOB’s

let my_blob = blob(3, 0x42);

my_blob += blob(5, 0x89);

my_blob.to_string() == "[4242428989898989]";

Mix two object maps together

let my_obj = #{ a:1, b:2 };

my_obj += #{ c:3, d:4, e:5 };

my_obj == #{ a:1, b:2, c:3, d:4, e:5 };

Add seconds to timestamps

let now = timestamp();

now += 42.0;

(now - timestamp()).round() == 42.0;