Free Hero Mesh

=== Instructions ===

For some instructions, a comma prefix means to operate on another object,
while the lack of the comma means to operate on itself; for some other
instructions, a comma prefix means to use signed instead of unsigned
arithmetic. An equal sign prefix usually means to write instead of read.

Anywhere an instruction is allowed, it may be one of these instructions, or
it may be a constant value, or reading/writing a variable (see the above
section about variables specific to objects), or a block instruction (see
Some instructions are block instructions; see the next section.
the next section for block instructions).

Many instructions are state-changing instructions; these instructions are
marked with ** in the summary line. Such instructions are not allowed to be
used on the same turn as the IgnoreKey instruction.

<function>
  Call a user-defined function (the name starts with a ampersand).

<global>  ( -- any )
  Read a global variable.

=<global>  ( any -- ) **
  Write a global variable.

<label>
  Define a label. Labels are local to the current class. (Label names
  always start with a colon.)

=<label>
  Go to a label. (Put the colon after the equal sign; this instruction,
  and the one below, are using a double sigil.)

,<label>
  Call a label as a subroutine; when it returns, comes back to here.

<function>
  Call a user-defined function.

.  ( x -- )

+  ( in1 in2 -- out )
  Add two numbers together.

-  ( in1 in2 -- out )
  Subtract in2 from in1.

  is no popup quiz. (Not implemented yet. Details described here might be
  changed when it is implemented.)

ret  ( -- )
  Exit the current subroutine. If this is a message block, it must either
  leave the stack as it is, or leave it but with one extra value pushed
  which will be the return value from the message call. (This is implied
  at the end of a code block.)
  at the end of a code block.) For a user defined function call, or a
  subroutine call, these restrictions are not applicable.

rot  ( x y z -- y z x )

-rot  ( x y z -- z x y )

rsh  ( in shift -- out )
  Logical right shift. If the shift amount is out of the range 0-31,