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Beau­tiful Racket / racket school 2019

Day 3

Mission

Imple­ment these language features:

  1. JavaScript-style data objects: a series of key-value pairs where the key is a string, the value is any expres­sion. The key & value are sepa­rated by a colon, and each key-value pair is sepa­rated by a comma.

    Hint: These most resemble Racket hash tables with strings as keys.

    var obj = {
        "foo" : 42,
        'dbl' : function(x) { x + x; },
        "bar" : { "zim" : 100, "zam" : "hooray" }
    };
    var obj = {
    "foo" : 42,
    'dbl' : func­tion(x) { x + x; },
    "bar" : { "zim" : 100, "zam" : "hooray" }
};
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  2. dotted object refer­ences like obj.bar.zim

    Hint: Treat the dotted object refer­ence as a single token. Notice that it can appear anywhere in the program that a vari­able name can. But you’ll have to do a little more work to turn it into a value.

    var dub = function(x) { x + x; };
    var obj = {
        "foo" : 42,
        'dbl' : function(x) { dub(x); },
        "bar" : { "zim" : 100, "zam" : "hooray" }
    };

    obj.foo; // 42
    obj.dbl; // #<procedure>
    obj.dbl(8); // 16
    obj.dbl(obj.foo); // 84
    obj.dbl(obj.bar.zim); // 200
    var dub = func­tion(x) { x + x; };
var obj = {
    "foo" : 42,
    'dbl' : func­tion(x) { dub(x); },
    "bar" : { "zim" : 100, "zam" : "hooray" }
};

obj.foo; // 42
obj.dbl; // #<proce­dure>
obj.dbl(8); // 16
obj.dbl(obj.foo); // 84
obj.dbl(obj.bar.zim); // 200
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Optional

  1. Make the assign­ment oper­a­tors = += -= work with dotted object nota­tion.

    var obj = {
      'foo' : "hello";
    };

    obj.foo = 50;
    obj.foo += 10;
    obj.foo; // 60
    var obj = {
  'foo' : "hello";
};

obj.foo = 50;
obj.foo += 10;
obj.foo; // 60
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  2. Make the incre­ment & decre­ment oper­a­tors work with dotted object nota­tion.

    var obj = {
      'foo' : 42;
    };

    obj.foo++; // 42
    obj.foo; // 43
    obj.foo--; // 43
    obj.foo; // 42
    var obj = {
  'foo' : 42;
};

obj.foo++; // 42
obj.foo; // 43
obj.foo–; // 43
obj.foo; // 42
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