Propeller Manual

2: Spin Language Reference – Operators
Multiply, Return Low ‘*’, ‘*=’
This operator is also called Multiply-Low, or simply Multiply. It can be used in both variable
and constant expressions. When used with variable expressions or integer constant
expressions, Multiply Low multiplies two values together and returns the lower 32 bits of the
64-bit result. When used with floating-point constant expressions, Multiply Low multiplies
two values together and returns the 32-bit single-precision floating-point result. Example:
X := Y * 8
Multiply-Low has an assignment form, *=, that uses the variable to its left as both the first
operand and the result destination. For example,
X *= 20 'Short form of X := X * 20
Here, the value of X is multiplied by 20 and the lowest 32 bits of the result is stored back in X.
The assignment form of Multiply-Low may also be used within expressions for intermediate
results; see Intermediate Assignments, page 147.
Multiply, Return High ‘
**’, ‘**=’
This operator is also called Multiply-High. It can be used in both variable and integer
constant expressions, but not in floating-point constant expressions. Multiply High multiplies
two values together and returns the upper 32 bits of the 64-bit result. Example:
X := Y ** 8
If Y started out as 536,870,912 (2
29
) then Y ** 8 equals 1; the value in the upper 32 bits of the
result.
Multiply-High has an assignment form,
**=, that uses the variable to its left as both the first
operand and the result destination. For example,
X **= 20 'Short form of X := X ** 20
Here, the value of X is multiplied by 20 and the upper 32 bits of the result is stored back in X.
The assignment form of Multiply-High may also be used within expressions for intermediate
results; see Intermediate Assignments, page 147.
Propeller Manual v1.1 · Page 153