Unary expressions

Gosu supports the following unary (single operand) expressions:

Numeric negation
Bit-wise NOT
Typeof expressions

The following sections describe these expressions. The value of a typeof expression cannot be fully determined at compile time. For example, an expression at compile time might resolve as a supertype. At run time, the expression may evaluate to a more specific subtype.

Numeric negation

Gosu uses the unary - operator before a number to indicate numeric negation. The operand must be a number data type. The result is always the same type as the original number.

Syntax

-value

Examples

Expression	Result
`-42`	`-42`
`-(3.14 - 2)`	`-1.14`

Bit-wise `NOT`

The bit-wise NOT operator treats a numeric value as a series of binary digits (bits) and inverts them. This behavior is different from the logical NOT operator (!), which treats the entire numeral as a single Boolean value. In the following example, the logical NOT operator assigns a Boolean value of true to x if y is false, or false if y is true:

x = !y

In the following example, the bit-wise NOT operator (~) treats a numerical value as a set of bits and inverts each bit, including the sign operator.

z = ~7

The decimal number 7 is the binary value 0111 with a positive sign bit. By using the bit-wise NOT, the expression ~7 evaluates to the decimal value -8. The binary value 0111 reverses to 1000, the binary value for 8, and the sign bit changes as well to produce -8.

Use the bit-wise NOT operation to manipulate a bit mask. A bit mask is a number or byte field that maintains the state of many items by flags mapping to each bit in the field.

`Typeof` expressions

Gosu uses the operator typeof to determine meta information about the type to which an expression evaluates. The operand can be any valid data type. The result is the type of the expression.