Can your programming language do this?

I recently read Joel Spolsky’s article “Can your programming language do this?” And I liked it so much that I decided to translate it. But not just like that, but add a little bit of myself. Namely, instead of examples in JavaScript (used by Joel in the original), I decided to write examples in C #, which is closer to me today. Actually the result and submit to the community under the cut.



Imagine, looking through your code, you come across two big blocks that look very similar. In fact, they are the same, just one of the blocks refers to “Spaghetti”, and the second to “Chocolate mousse”.
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// -    Main   
Console.WriteLine(“I’d like some Spaghetti!”);
Console.WriteLine(“I’d like some Chocolate Moose!”);

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, :

public void SwedishChief(string food)
{
    Console.WriteLine(string.Format(“I’d like some {0}!”, food));	
}

SwedishChief(“Spaghetti”);
SwedishChief(“Chocolate Moose”);

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, , , BoomBoom, — PutInPot. , .

Console.WriteLine(“get the lobster”);
PutInPot(“water”);
PutInPot(“lobster”);

Console.WriteLine(“get the chicken”);
BoomBoom(“chicken”);
BoomBoom(“coconut”);

, . , , .

//             :
//        ,  
//          alert.
public static T Alert<T>(T message)
{
     Console.WriteLine(message.ToString());
     return message;
}

public void Cook(string ingredientOne, string ingredientTwo, Action<string> function)
{
    Console.WriteLine(string.Format("get the {0}",ingredientOne));
    function(ingredientOne);
    function(ingredientTwo);
}

Cook(“lobster”, “water”, PutInPot);
Cook(“chicken”, “coconut”, BoomBoom);

! .

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… , PutInPot BoomBoom. (inline), - .

Cook("lobster",
          "water",
          x => Alert("pot " + x));

Cook("chicken",
          "coconut",
          x => Alert("boom " + x));

, . , , , Cook()…

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...
var list = new List<int> { 1, 2, 3 };

for (var i = 0; i < list.Count; i++)
{
     list[i] = list[i] * 2;
}

foreach (var el in list)
{
    Alert(el.ToString());
}
...

- , , .

public static void Map<T>(Func<T, T> action, IList<T> list)
{
    for (var i = 0; i < list.Count; i++)
        list[i] = action(list[i]);
}

, :

...
Map((x) => x * 2, list);
Map(Alert, list);
...

, , - .

…
Alert(Sum(list));
Alert(Join(new[] { "a", "b", "c" }));
...

public static int Sum(IEnumerable<int> list)
{
    var sum = 0;
    foreach (var el in list)
        sum += el;

    return sum;
}

public static string Join(IEnumerable<string> list)
{
    var result = string.Empty;
    foreach (var el in list)
        result += el;

    return result;
}

Sum Join , - , .

public static T Reduce<T>(Func<T, T, T> func, IEnumerable<T> list, T init)
{
    var accumulator = init;
    foreach (var el in list)
        accumulator = func(accumulator, el);

    return accumulator;
}

public static int Sum(IEnumerable<int> list)
{
    return Reduce((x, y) => x + y, list, 0);
}

public static string Join(IEnumerable<string> list)
{
    return Reduce((a,b) => a + b, list, string.Empty);
}

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