numerical interval matching in case statements

[podhrmic]

Hello!
I have a large case statement that handles IO memory access - something like:

// addr is Bit#(32)
case (addr)
         gpio_addr:
            // GPIO handling
         uart_reg_addr_tx:
           // Write a byte to serial port
         uart_reg_addr_rx:
            // Receive data from serial port
....

Is there a way to match on an interval of addr ? For example:

case (addr)
  (uart_reg_addr_base <= addr || addr <= uart_reg_addr_max):
      // handle UART IO in a separate function call
...

If not, is there another way to split a large pattern match like above?

[podhrmic]

Looks like

case (e1)
  e2, e3: s2;
...

is pretty close. Although it is still an enumeration, which can get tedious.

[quark17]

Each e is an expression, though!

In Verilog, there is an idiom like this:

case (1)
  (x && y): ...;
  (z > 12): ...;
  ...
endcase

It's a priority encoder that takes the first arm whose condition is true. In BSV, you can do the same thing:

case (True)
   (gpio_base <= addr && addr <= gpio_max): ...
   (uart_base <= addr && addr <= uart_max): ...
   ....
endcase

In general, this pattern in BSV:

case (e)
  e1: ...
  e2: ...
  ...
endcase

is a priority encoder that picks the first arm whose expression eN evaluates to the same value as the expression e of the case. Any of these (including e) can be arbitrary expressions and not just a variable name or numeric literal.

[podhrmic]

Awesome! Thanks for the explanation.