public static SExp Setq(SExp[] vals, Environment env)
{
Utilities.CheckArguments(vals, args=>args.Length==2, "set!: ");
if (!(vals[0] is Identifier))
{
string msg = "The first argument must be identifier.";
throw new TypeNotMatchException(msg);
}
Identifier name = vals[0] as Identifier;
SExp val = Utilities.Eval(vals[1], env);
if (!env.Reassign(name.Value as string, val))
{
string msg =
string.Format("Identifier '{0}' is undefined.", name);
throw new IdentifierNotDefinedException(msg);
}
return name;
}
