 env ] =
   eval[ BOUND-VARIABLE, env ]
eval_claw[ (EXPRESSION), env ] =
   eval[ EXPRESSION, env ]
eval_claw[ (VARIABLE EXPRESSION), env ] =
   eval[ EXPRESSION, env ]

ext_claw_env[ BOUND-VARIABLE, env ] = env
ext_claw_env[ (EXPRESSION), env ] =
   env-after-eval[ EXPRESSION, env ]
ext_claw_env[ (VARIABLE EXPRESSION), env ] =
   extend-env[ env-after-eval[ EXPRESSION, env ],
              VARIABLE boundto eval[ EXPRESSION, env ]]
</PRE>

<H1>Implementation</H1>

<P>The full implementation plus the validat