[Pharo-users] scope shadowing problem.

Nov. 14, 2016

      Is there a way to stop Pharo from preventing me from shadowing blocks?

[:superenv |
	 |env|
	 env := Dictionary new.

    [:superenv |
        |env|
        env := Dictionary new.
        [:superenv |
            |env|
            env := Dictionary new.

            "..."
        ] value: env.
    ] value: env.
] value: nil.

It says superenv name already defined, even though that is the whole point,
I want to demonstrate dynamic links, eg:

var env_get = function(env, varname) {
    var tenv = env;

    while (true) {    
        if (tenv.hasOwnProperty(varname)) {
            return tenv[varname];
        } else {
            if (tenv.superenv == null) {
                throw "no such variable" + tenv;
            } else {
                tenv = tenv.superenv;
            }
        }
    }
};

(function(superenv) {
    var env = {
        'superenv': superenv,
        'one': 1
    };

    console.log(env_get(env, "one"));

    (function(superenv) {
        var env = {
            'superenv': superenv,
            'two': 2
        };
        console.log(env_get(env, "one"));
        console.log(env_get(env, "two"));

        (function(superenv) {
            var env = {
                'superenv': superenv,
                'three': 3
            }                        
            console.log(env_get(env, "one"));
            console.log(env_get(env, "two"));                
            console.log(env_get(env, "three"));
        })(env);
    })(env);
})(null);

in JavaScript

and 

(defun env_get (env varname) (let
    ((tenv))
    (setq tenv env)

    (loop (let
        ((val))

        (setq val (gethash varname tenv))
        (if val
            (return val)
            (let
                ((superenv))
                (setq superenv (gethash 'superenv tenv))

                (if superenv
                    (setq tenv superenv)
                    (return 'undefined)
                )
            )
        )
    ))
))

((lambda (superenv) (let 
    ((env))

    (setq env (make-hash-table))
    (setf (gethash 'superenv env) nil)
    (setf (gethash 'one env) 1)

    (print (env_get env 'one))
    (print (env_get env 'two))
    (print (env_get env 'three))     

    ((lambda (superenv) (let        
        ((env))

        (setq env (make-hash-table))
        (setf (gethash 'superenv env) superenv)
        (setf (gethash 'two env) 2)

        (print (env_get env 'one))
        (print (env_get env 'two))
        (print (env_get env 'three))  

        ((lambda (superenv) (let        
            ((env))

            (setq env (make-hash-table))
            (setf (gethash 'superenv env) superenv)
            (setf (gethash 'two env) 2)
            (setf (gethash 'three env) 3)

            (print (env_get env 'one))
            (print (env_get env 'two))
            (print (env_get env 'three))                    
        )) env)                    
    )) env)    
)) nil)

in Lisp.

--
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[Pharo-users] scope shadowing problem.

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