.pg
.x case
.x do
.x break
.x default
.x end
.lt
------------------------------------------------------------------------
CASE	index <label-list> [BASE=base] [TYPE=type] DO
  label_1:
    ...
  label_2:
    ...

  label_n:
    ...
  DEFAULT
    ...
END
------------------------------------------------------------------------
.el
.b 3
These macros implements the CASEB, CASEW or CASEL VAX instruction, generates
the case table from a list of branch distinations and calculates the index
limit. 
.b
If ^&base\& is not specified, #0 is assumed.
If ^&type\& is not specified, L is assumed. 
.b
The _._._. statements can take on two forms:
.b
.ls
.le
.lt
	statements
	break
.el
.b
The BREAK macro will generate a branch to the end of the case structure. If the
branch displacement for CASE is BYTE, a BRB instruction will be generated, if
the branch displacement is WORD, a BRW instruction will be generated, and if
the branch displacement is LONG, a JMP instruction will be genereated. 
.le
.lt
	statements
.el
.b
If no BREAK macro is used, the program will continue to execute into
the next case label.
.els
The default branch displacement for CASE is WORD (see BRANCH). 
.b
The DEFAULT macro begins code statements for the default case (i.e. when the
case index is outside the _<^&label-list\&_> supplied). The DEFAULT macro and
it's corresponding code statements are optional. 
.b
For every CASE macro specified, a corresponding END macro must also be
specified. The END macro corresponding to the CASE macro will generate the
appropriate labels. 
.b
.tp 5
For example:
.b
.lt
	case r1 <one,two,three> base=#1 do
	one:
		statements-1
		break
	two:
		statements-2
		break
	three:
		statements-3
		break
	DEFAULT
		statements-0
	end
.el
.b
will generate the following code:
.b
.lt
		casel	r1,#1,#<<30001$-30000$>/2>-1
	30000$:
		.word	one-30000$
		.word	two-30000$
		.word	three-30000$
	30001$:
		brw	20000$
	one:
		statements-1
		brw	20001$
	two:
		statements-2
		brw	20001$
	three:
		statements-3
		brw	20001$
	20000$:
		statements-0
	20001$:
.el