.common "hp_com.r.i";
.scanner getchar;
.symbol char;

.ext_term
      NEWLINE
      EOS
      ;

expression ->
      { constant | command }
      (     NEWLINE.
         |  EOS.        ? call print (ERROUT, "*c: unrecognized command*n.",
                        ?    char)
         )
      ;

constant ->
                        ! floating ctod
                        ! while (char == ' 'c)
                        !    call getchar
      '.'               ! call push (ctod (line, scanptr))
                        ! scanptr -= 1
   |  '0' : '9'         ! call push (ctod (line, scanptr))
                        ! scanptr -= 1
      ;

command ->              ! integer i
                        ! logical sound
                        ! while (char == ' 'c)
                        !    call getchar
      'p'               ! if (sound (1))
                        !    call print (STDOUT, "*d*n.", stack (sp))
   |  'P'               ! for (i = 1; i <= sp; i += 1)
                        !    call print (STDOUT, "*d*n.", stack (i))
   |  '+'               ! if (sound (2)) {
                        !    stack (sp - 1) += stack (sp)
                        !    sp -= 1
                        !    }
   |  '-'               ! if (sound (2)) {
                        !    stack (sp - 1) -= stack (sp)
                        !    sp -= 1
                        !    }
   |  '*'               ! if (sound (2)) {
                        !    stack (sp - 1) *= stack (sp)
                        !    sp -= 1
                        !    }
   |  '/'               ! if (sound (2)) {
                        !    stack (sp - 1) /= stack (sp)
                        !    sp -= 1
                        !    }
   |  '^'               ! if (sound (2)) {
                        !    stack (sp - 1) = stack (sp - 1) ** stack (sp)
                        !    sp -= 1
                        !    }
   |  'd'               ! if (sound (1))
                        !    sp -= 1
   |  'D'               ! sp = 0
   |  '<'               ! if (sound (2)) {
                        !    if (stack (sp - 1) < stack (sp))
                        !       stack (sp - 1) = 1.0
                        !    else
                        !       stack (sp - 1) = 0.0
                        !    sp -= 1
                        !    }
   |  '='               ! if (sound (2)) {
                        !    if (stack (sp - 1) == stack (sp))
                        !       stack (sp - 1) = 1.0
                        !    else
                        !       stack (sp - 1) = 0
                        !    sp -= 1
                        !    }
   |  '>'               ! if (sound (2)) {
                        !    if (stack (sp - 1) > stack (sp))
                        !       stack (sp - 1) = 1.0
                        !    else
                        !       stack (sp - 1) = 0
                        !    sp -= 1
                        !    }
   |  '&'               ! if (sound (2)) {
                        !    if (stack (sp - 1) ~= 0 & stack (sp) ~= 0)
                        !       stack (sp - 1) = 1.0
                        !    else
                        !       stack (sp - 1) = 0.0
                        !    sp -= 1
                        !    }
   |  '|'               ! if (sound (2)) {
                        !    if (stack (sp - 1) ~= 0 | stack (sp) ~= 0)
                        !       stack (sp - 1) = 1.0
                        !    else
                        !       stack (sp - 1) = 0.0
                        !    sp -= 1
                        !    }
   |  '~'               ! if (sound (1))
                        !    if (stack (sp) ~= 0)
                        !       stack (sp) = 0
                        !    else
                        !       stack (sp) = 1.0
      ;