Programming Language Principles

Homework 6

1. Build the functional graph for the binary number 101.101,
   according to the attribute grammar for binary numbers
   developed in class. Be sure to show the value propagation through
   the tree clearly.

2. Build the AST for the following Tiny program:
 
   program sum:
     assign s:=0;
     assign i:=1;
   while not (i=10) do
     assign s:=s+read;
     assign i:=i+1;
   od
   output s
   end sum

    Place next to each tree node the necessary attributes.
    To simplify things, limit this to the 'code', 'next', and
    'top' attributes, as illustrated in the example shown at
    the end of Lecture 3.  Keep inherited attributes on each tree
    node's left, and synthesized attributes on the right.
    Write down the actual values of the attributes, i.e. show the
    result of propagating the values through the functional graph.
    DO NOT depict the functional graph itself.  As suggested in
    class, depict the code file "on the side", i.e. don't make a
    copy of the code file at each tree node.  Instead, at each
    tree node, indicate the line number of the machine instruction
    (if any) that is being added to the code file.

3. Modify the attribute grammar for Tiny, so that "read" is no longer
    an intrinsic function, but instead a statement.
    Instead of

          assign i := read;

    we would have

          read(i);

    The read statement would handle exactly ONE indentifier.