See Also

Arithmetic operators are used to perform arithmetic addition and subtraction operations on groups and numbers in AHDL Boolean expressions. The following arithmetic operators are used in Boolean expressions:

+1

-a[4..1]

+

count[7..0] + delta[7..0]

-

rightmost_x[] - leftmost_x[]

The unary plus (+) and minus (-) are prefix operators. The + operator does not affect its operand, but you may use it for documentation purposes (that is, to indicate a positive number). The - operator interprets its operand as a binary representation of a number if it is not already a number. It then performs a two's complement unary-minus operation on the operand.

The following rules apply to the other arithmetic operators:

• Operations are performed between two operands, which must be groups of nodes or numbers.

• If both operands are groups of nodes, the groups must be the same size.

• If both operands are numbers, the shorter number is sign-extended to match the size of the other operand.

• If one operand is a number and the other is a group of nodes, the number is truncated or sign-extended to match the size of the group. If any significant bits are truncated, the Compiler generates an error message.

When you add two groups together on the right of a Boolean equation with the + operator, you can place a 0 on the left of each group to sign-extend the width of the group. This method provides an extra bit of information to the group on the left of the equation that can be used as a carry-out signal. Example You can name Boolean operators and comparators in AHDL files to make it easy to enter resource assignments and to interpret the Equations Section of the Text-Format Report File (.rpt) or HTML-Format Report File (.htm). For more information, go to Naming a Boolean Operator or Comparator. The arithmetic operators that are supported in Boolean expressions are a subset of the arithmetic operators supported in arithmetic expressions.

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