Lab 10🔗

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1 Fuzzing!🔗

Let’s use your random term generation to find ... something?

Copy your interp function from Assignment 4 or 5, along with its helper functions. Try calling interp on one of your random terms.

Write a recursive function run-trials that accepts a number of trials and a maximum depth and runs the given number of trials, calling interp on a random term each time. Use a with-handlers block to compute what fraction of random programs complete without an error.

Here’s an example of using with-handlers:

#lang racket

(define (maybe-crash)
  (/ 10 (random 4)))

(define (do-a-thing)
  (with-handlers ([;; which exceptions should we catch?
                   exn:fail?
                   ;; what should we return when we catch one?
                   (λ (exn)
                     ;; let's display the message and return #f
                     (eprintf "~a\n" (exn-message exn))
                     #f
                     )])
    (maybe-crash)))

(build-list 10 (λ (_) (do-a-thing)))

Refine your function random-term so that it only produces "closed" CFAEs: that is, those with no free variables. To do this, your function must accept a list of currently-bound variables, so that it can be sure to pick varrefs only from this list. Call this function random-closed-term.
Shrink the language by omitting numbers, booleans, strings, and ’if’, and fixing the number of arguments at one so that no errors can occur. Then, search for a term that loops forever!

2 SMoL Tutorial🔗

Continuing with the SMoL tutorial, do the next two sections: "mutvars1" and "mutvars2".

At the end of each section you will be prompted to save a PDF file of the completed tutor; do that! For lab credit, you should be prepared to show these two PDFs, in addition to the code you produced to solve the problems above.

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