public static plt_node eval_node(plt_node input)
{
plt_tail ret;
do
{
if (input != null)
{
ret = input.eval();
}
else
{
ret = plt_tail.nil;
}
if (ret.is_tail)
{
input = ret.value;
}
} while (ret.is_tail);
return(ret.value);
}
public override plt_tail eval()
{
return(exp.eval());
}
public static plt_node eval_node(plt_node input)
{
plt_tail ret;
do
{
if (input != null){
ret = input.eval();
}
else {
ret = plt_tail.nil;
}
if (ret.is_tail)
{
input = ret.value;
}
} while (ret.is_tail);
return ret.value;
}
public override plt_tail eval()
{
if (_member.Count == 0)
{
return(plt_tail.nil);
}
plt_node afirst = plt_node.eval_node(_member[0]);
if (afirst == null)
{
return(plt_tail.nil);
}
{//特殊的函数
//特殊情况-不解释参数
if (ReferenceEquals(afirst, plt_lambda.quote))
{
if (_member.Count < 2)
{
return(plt_tail.nil);
}
return(new plt_tail(_member[1], false));
}
if (ReferenceEquals(afirst, plt_lambda.make_lambda))
{
plt_list_lambda ret = new plt_list_lambda();
ret.arg_name = _member[1] as plt_list;
ret.exp = _member[2];
return(new plt_tail(ret, false));
}
if (ReferenceEquals(afirst, plt_lambda.cond))
{
for (int i = 1; i + 1 < _member.Count; i += 2)
{
plt_node _if = plt_node.eval_node(_member[i]);
if (_if != null)
{
return(new plt_tail(_member[i + 1], true));
}
}
}
//宏 不解释参数
plt_lambda lismacro = afirst as plt_lambda;
if (lismacro != null && lismacro.ismacro)
{
lismacro.mix_env(this);
return(lismacro.eval());
}
}
plt_list args_eval = new plt_list();
args_eval.add(afirst);
for (int i = 1; i < _member.Count; i++)
{
args_eval.add(plt_node.eval_node(_member[i]));
}
plt_lambda func = afirst as plt_lambda;
if (func != null)
{
func.mix_env(args_eval);
}
return(afirst.eval());
}