Expressions

An ``expression'' combines signals using a collection of operators. These operators include:

• boolean operators (``and'', ``or'', ``not'' and ``xor''),
• conditional operators (``if-then-else'', ``case'' and ``switch'')
• arithmetic operators (``+'', ``-'', ``*'', ``/'', ``mod'', and shifts)
• comparison operators (``='', ``<'', ``>'', ``>='', ``<='')
• set operators (union, integer subrange and inclusion)
• vector operators (concatenation, subrange)
• conversion operations (integer to bit vector and vice versa)

Since signals are sequences of values, all of these operators apply to the elements of a sequence one-by-one. Thus, if

$$\begin{eqnarray*} x &=& x_1,x_2,x_3,\ldots\\ y &=& y_1,y_2,y_3,\ldots \end{eqnarray*}$$

and $\cdot$ is a binary operator, then

$$x \cdot y = (x_1 \cdot y_1),(x_2 \cdot y_2),(x_3 \cdot y_3),\ldots$$

The following describes the various operators as they apply to individual values.