int test_environment()
{
symbol *sa = new_symbol("a");
symbol *sb = new_symbol("b");
symbol *sc = new_symbol("c");
symbol *sx = new_symbol("x");
symbol *sy = new_symbol("y");
symbol *sz = new_symbol("z");
symbol *sn = new_symbol("n");
integer *i10 = new_integer(10);
integer *i20 = new_integer(20);
integer *i30 = new_integer(30);
integer *i40 = new_integer(40);
integer *i50 = new_integer(50);
integer *i60 = new_integer(60);
list *vara = cons(sa, cons(sb, cons(sc, NULL)));
list *varx = cons(sx, cons(sy, cons(sz, NULL)));
list *val10 = cons(i10, cons(i20, cons(i30, NULL)));
list *val40 = cons(i40, cons(i50, cons(i60, NULL)));
environment *env = NULL;
env = extend_env(vara, val10, env);
assert(generic_equal(lookup_var_val(sa, env), cons(sa, i10)));
assert(generic_equal(lookup_var_val(sb, env), cons(sb, i20)));
assert(generic_equal(lookup_var_val(sc, env), cons(sc, i30)));
env = define_var_val(sx, i40, env);
assert(generic_equal(lookup_var_val(sa, env), cons(sa, i10)));
assert(generic_equal(lookup_var_val(sb, env), cons(sb, i20)));
assert(generic_equal(lookup_var_val(sc, env), cons(sc, i30)));
assert(generic_equal(lookup_var_val(sx, env), cons(sx, i40)));
assert(generic_equal(lookup_var_val(sy, env), NULL));
env = set_var_val(sx, i50, env);
assert(generic_equal(lookup_var_val(sa, env), cons(sa, i10)));
assert(generic_equal(lookup_var_val(sb, env), cons(sb, i20)));
assert(generic_equal(lookup_var_val(sc, env), cons(sc, i30)));
assert(generic_equal(lookup_var_val(sx, env), cons(sx, i50)));
assert(generic_equal(lookup_var_val(sy, env), NULL));
env = extend_env(varx, val40, env);
assert(generic_equal(lookup_var_val(sa, env), cons(sa, i10)));
assert(generic_equal(lookup_var_val(sb, env), cons(sb, i20)));
assert(generic_equal(lookup_var_val(sc, env), cons(sc, i30)));
assert(generic_equal(lookup_var_val(sx, env), cons(sx, i40)));
assert(generic_equal(lookup_var_val(sy, env), cons(sy, i50)));
assert(generic_equal(lookup_var_val(sz, env), cons(sz, i60)));
assert(generic_equal(lookup_var_val(sn, env), NULL));
return 1;
}
///////////////////////////////////////////////////////////////////
//eval
//requires two arguments:exp & tail_context
///////////////////////////////////////////////////////////////////
cellpoint eval(void)
{
if (is_true(is_self_evaluating(args_ref(1)))){
reg = args_ref(1);
}else if (is_true(is_variable(args_ref(1)))){
reg = args_ref(1);
args_push(current_env);
args_push(reg);
reg = lookup_var_val();
}else if (is_true(is_quoted(args_ref(1)))){
args_push(args_ref(1));
reg = quotation_text();
}else if (is_true(is_assignment(args_ref(1)))){
args_push(args_ref(1));
reg = eval_assignment();
}else if (is_true(is_definition(args_ref(1)))){
args_push(args_ref(1));
reg = eval_definition();
}else if (is_true(is_if(args_ref(1)))){
//eval if expression with the second argument (tail_context)
reg = args_ref(1);
args_push(args_ref(2));
args_push(reg);
reg = eval_if();
}else if (is_true(is_lambda(args_ref(1)))){
args_push(args_ref(1));
reg = eval_lambda();
}else if (is_true(is_begin(args_ref(1)))){
args_push(args_ref(1));
reg = begin_actions();
//eval the actions of begin exp with the second argument (tail_context)
args_push(args_ref(2));
args_push(reg);
reg = eval_sequence();
}else if (is_true(is_cond(args_ref(1)))){
args_push(args_ref(1));
reg = cond_2_if();
//eval the exp with the second argument (tail_context)
args_push(args_ref(2));
args_push(reg);
reg = eval();
}else if (is_true(is_and(args_ref(1)))){
reg = args_ref(1);
args_push(args_ref(2));
args_push(reg);
reg = eval_and();
}else if (is_true(is_or(args_ref(1)))){
reg = args_ref(1);
args_push(args_ref(2));
args_push(reg);
reg = eval_or();
}else if (is_true(is_let(args_ref(1)))){
//convert let to combination
args_push(args_ref(1));
reg = let_2_combination();
//evals the combination
args_push(args_ref(2));
args_push(reg);
reg = eval();
}else if (is_true(is_letstar(args_ref(1)))){
//convert let* to nested lets
args_push(args_ref(1));
reg = letstar_2_nested_lets();
//evals the nested lets
args_push(args_ref(2));
args_push(reg);
reg = eval();
}else if (is_true(is_application(args_ref(1)))){
//computes operator
args_push(args_ref(1));
reg = operator();
args_push(a_false);
args_push(reg);
reg = eval();
stack_push(&vars_stack, reg);
//computes operands
args_push(args_ref(1));
reg = operands();
args_push(reg);
reg = list_of_values();
//calls apply with the second argument (tail_context)
args_push(args_ref(2));
args_push(reg);
args_push(stack_pop(&vars_stack));
reg = apply();
}else {
printf("Unknown expression type -- EVAL\n");
error_handler();
}
args_pop(2);
return reg;
}