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Beau­tiful Racket / racket school 2019

Day 3

Final boss battle

Let’s make a language called scriptish of suffi­cient sophis­ti­ca­tion to run this test file.

We’ll get there by building the language in small pieces. As you work through, crib as many ideas as you like from previous prob­lems. There’s more than one way to do it. You may also find that later features require you to recon­sider choices you made earlier.

Most of the features build on what we’ve already learned. Some require new tech­niques that will require dipping into the Racket docs. But in your LOP career, knowing how to surmount new obsta­cles will be a crit­ical skill.

BTW, indenting and syntax coloring of our sample code might look incor­rect at times because DrRacket will be applying the default Racket rules. Don’t panic.

scriptish/test.rkt
#lang scriptish

var x = 42;
var s = "string";

x + x; // prints 84
s + x; // prints "string42"

var thing = {
    "foo" : 42,
    'bar' : function(x) {
        return x + 15;
    }
};

thing.foo; // prints 42
thing.bar; // prints #<procedure:...test.rkt:11:12>
thing.bar(3); // prints 18

if ( thing.foo == 42 ) {
    // prints "The correct answer is 42"
    alert("The correct answer is " + thing.foo);
} else {
    alert("Nope");
}

var idx = 0;
while ( idx != 50 ) {
    if ( thing.bar(idx) == 35 ) {
       // prints "Calamity at 20!"
       alert("Calamity at " + idx + "!");
    }
    idx++;
} 
#lang scrip­tish

var x = 42;
var s = "string";

x + x; // prints 84
s + x; // prints "string42"

var thing = {
    "foo" : 42,
    'bar' : func­tion(x) {
        return x + 15;
    }
};

thing.foo; // prints 42
thing.bar; // prints #<proce­dure:...test.rkt:11:12>
thing.bar(3); // prints 18

if ( thing.foo == 42 ) {
    // prints "The correct answer is 42"
    alert("The correct answer is " + thing.foo);
} else {
    alert("Nope");
}

var idx = 0;
while ( idx != 50 ) {
    if ( thing.bar(idx) == 35 ) {
       // prints "Calamity at 20!"
       alert("Calamity at " + idx + "!"); 
    }
    idx++;
}
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Result:

84
"string42"
42
#<procedure:...ptish-demo/test.rkt:11:12>
18
ALERT! The correct answer is 42
ALERT! Calamity at 20! 
84
"string42"
42
#<proce­dure:...ptish-demo/test.rkt:11:12>
18
ALERT! The correct answer is 42
ALERT! Calamity at 20!
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Summary

Welcome to the jungle.

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