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c#.netironscheme

Resetting IronScheme Engine in C#

Is there a way to "reset" the IronScheme engine? I'm essentially aiming to ensure that successive calls to string.Eval() are executed independently.

For example, I want to be execute

"(define x 1.0) (+ x 5.0)".Eval()

then reset, and have the call

"(+ x 3.0)".Eval()

fail as it would if it were executed by itself.

Even better would be a way to give each of n concurrent threads its own independent space in which to execute.

Solution

  • You have 2 options for the REPL (with libraries it will not even allow you to write such code ;p).

    1: Reset the interaction environment.

    This can be done with (interaction-environment (new-interaction-environment)).

    Sample:

    > (define x 5) (+ x 5)
10
> (interaction-environment (new-interaction-environment))
> (+ x 5)
Unhandled exception during evaluation:
&undefined
&message: "attempted to use undefined symbol"
&irritants: (x)

    2: Create a new interaction environment that you hold on to in C#.

    If you want to concurrent environments, this is probably the best option. I use this approach for the IronScheme online evaluator.

    Sample: 

    "(define x 1.0) (+ x 5.0)".Eval();
var env = "(new-interaction-environment)".Eval();
"(+ x 3.0)".EvalWithEnvironment(env);

    Possible solution:

    Func<object> reset = 
   "(lambda () (interaction-environment (new-interaction-environment)))".
   Eval<Callable>().Call;

"(define x 1.0) (+ x 5.0)".Eval();

reset();

"(+ x 5.0)".Eval();