APPENDIX A: IMP80 Syntax


KEY
      ::=  A | B | C | D | E | F | G | H | I | J | K | L | M |
                   N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
                   a | b | c | d | e | f | g | h | i | j | k | l | m |
                   n | o | p | q | r | s | t | u | v | w | x | y | z

       ::=  0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

     ::=  {newline character}

         ::=  {| character}

   ::=  ! | " | # | $ | % | & | ' | ( | ) | * | + | , | - |
                   . | / | : | < | = | > | ? | @ | [ | ] | \ | ^ | _ |
                   ` | ~ | ; | <letter> | <digit> | <bar>

        ::=  []...

     ::=  %comment   | !  

     ::=   []...



      ::=   | 

        ::=   []...

    ::=   [, ]...

   ::=  [] 

        ::=  . []

   ::=  [] [] [@ ]

  ::=   _ ... |  ' ... '

      ::=   | 

  ::=  '  ' | M' ... '

   ::=  " []... "




       ::=   |  |  |
                   <char const> | <str const>

        ::=  + | - | \ | ~

       ::=  = | == | <- | ->

        ::=  + | -

       ::=   | -> | == | \== | ##

       ::=  = | # |  \= | <> | > | >= | < | <=

          ::=  * | / | // | + | - | ** | **** | \ | \\ | >> | << |
                   ! | !! | & | .

         ::=  (  [, ]... )

       ::=  _  []




     ::=   [] []... |  | (  )

        ::=  []  [ ]... 

       ::=  (  ) | (*)

   ::=   []

   ::=  =  [, ]...

       ::=  [[%array] %name]  |
                   %array [%format] <adecln> 

      ::=    [,  ]...

     ::=  [[%array] %name]  | %array  

 ::=  (  [%or ]... )

   ::=   [, ]...



       ::=    | 

       ::=  (  ) | 

       ::=  %integer | %real | %long %real

        ::=  %integer | %real | %long  | %byte [%integer] |
                   %short [%integer] | %half [%integer] | %string<count>

       ::=   | %record 

       ::=   [%alias "  "]

   ::=   [, ]...

     ::=   [= ]

      ::=  [[%array] %name] [%spec]  [, ]... |
                   %array [%format] [%spec] <oname> <bpair>[<constlist>]




          ::=  %fn | %function | %map

          ::=  %routine |   

       ::=   [[%array] %name]  |
                   <rt> [%name] <namelist> [<fpp>] |
                   %name <namelist> 

         ::=  (  [, ]... )

       ::=   : 

       ::=  (  [, ]... )

        ::=  %own | %external | %constant | %const

<%sed>        ::=  %system | %external | %dynamic

     ::=  %of %program | %of %file | %of %list




  ::=  [%and ]... | [%or ]...

          ::=     [ ] |
                   ( <sc> <restofcond> ) |
                   %not <sc> 

  ::=  [%and ]... | [%or ]...

<%wf>         ::=  %while   | 
                   %for <name> = <expr> , <expr> , <expr>

<%iu>         ::=  %if | %unless




          ::=   [] []...
                       [<assop> <expr>] [%and <ui>] |
                   -> <name> [<app>] |
                   %return |
                   %result <assop> <expr> | 
                   %monitor [%and <ui>] |
                   %stop |
                   %signal [%event] <const> [, <expr>] |
                   %exit |
                   %continue

          ::=  <%iu>   

    ::=  [%then] %start | %then  []

        ::=  %else %start |
                   %else <ci> |
                   %else <ui>




    ::=  <%iu>   |
                   %until <sc> <restofcond> |
                   <%wf>

           ::=  ; | 

     ::=  ...



          ::=  %begin  |
                   <xtype> <decln> <s> |
                   %record %format <name> <rfdeclistor> <s> |
                   [<%sed>] <rt> [%spec] <name> [<fpp>] <s> |
                   <xown> <xtype> <owndec> <s> |
                   %include " <text> " |
                   %switch <namelist> <bpair>
                       [, <namelist> <spair>]... <s> |
                   %on [%event] [, <integer>]... %start <s> |
                   <ui> [<restofss>] <s> |
                   <ci> <s> |
                   %finish [<else>] <s> |
                   [<%wf>] %cycle <s> |
                   %repeat [%until <sc> <restofcond>] <s> | 
                   <name> [<app>] : |
                   <name> (*) : |
                   %list <s> |
                   %end [<endlist>] <s> | 
                   <comment> |
                   <s> 




Notes


KEY

* In the above syntax, items in italics are non-terminals, '|' separates
  alternatives, '::=' means 'is defined as', items enclosed in [..]
  brackets are optional, and items followed by '...' can be repeated one
  or more times.  All other characters stand for themselves, except that
  {...} indicates a "descriptive" definition, involving a newline
  character or a character used in the statement of the syntax itself.

* The case of letters is ignored in IMP80 programs except within
  character constants.

* Space characters are only significant within character constants or
  following a keyword (%real, %if, %unless, %end, %not, etc.).

* <type> definition: not all the types may be available in some
  implementations.

* {EMAS IMP80: <type> definition: <count> replaced by [<count>]}

* {IMP77: <op> definition: ** | **** replaced by ^ | ^^ . }



* Text preceded by '{', terminated by '}' and appearing between
  syntactic elements of a program is treated as a comment.  Such a
  comment is also terminated by a newline character.

* IMP80 statements can be continued on the next line with %c.  The %c is
  not required if the break comes immediately after a comma.
  {IMP77: comment statements cannot be continued.}