'SOFTWARE ENGINEERING'에 해당되는 글 21건

1.Describe Function Behavior Precisely

// Return the number of lines in this file.
var CountLines = function (filename,  reply)
{
    //# remove everything after the second '*'
    name = '*'.join(line.split('*')[2]);

}

// Count how many newline bytes ('\n') are in the file.
var CountLines = function (filename,  reply)
{
    //# remove everything after the second '*'
    name = '*'.join(line.split('*')[2]);

}

// Rearrange 'v' so that elements < pivot come before those >= pivot;
// Then return the largest 'i' for which v[i] < pivot (or -1 if none are < pivot)
var Partition = function (filename,  reply)
{
    //# remove everything after the second '*'
    name = '*'.join(line.split('*')[2]);

}

// Example: Partition([8 5 9 8 2], 8) might result in [5 2 | 8 9 8] and return 1
var Partition = function (filename,  reply)
{
    //# remove everything after the second '*'
    name = '*'.join(line.split('*')[2]);

}

1.Comment the Flaws in Your Code

// Enforce limits on the Reply as stated in the Request,
// such as the number of items returned, or total byte size, etc.
var CleanReply = function (request,  reply)
{
/*    Marker Typical meaning
    TODO: Stuff I haven’t gotten around to yet
    FIXME: Known-broken code here
    HACK: Admittedly inelegant solution to a problem
    XXX: Danger! major problem here*/

}

TODO : 아직 하지 않은 일

FIXME:  오동작을 일으킨다고 알려진 코드

HAXK : 아름답지 않은 해결책

XXX: 위험! 여기 큰 문제가 있다.

TextMate : ESC

2.Comment on Your Constants

/// Make sure 'reply' meets the count/byte/etc. limits from the 'request'
var EnforceLimitsFromRequest = function (request,  reply)
{
    NUM_THREADS = 8     ;

    NUM_THREADS = 8 // as long as it's >= 2 * num_processors, that's good enough.

    // Impose a reasonable limit - no human can read that much anyway.
    var  MAX_RSS_SUBSCRIPTIONS = 1000;

    var image_quality = 0.72; // users thought 0.72 gave the best size/quality tradeoff

}

3.Don’t Comment Bad Names—Fix the Names Instead

void CleanReply(Request request, Reply reply); // comment for a function named CleanReply():

void EnforceLimitsFromRequest(Request request, Reply reply);
/*This function name is more “self-documenting.” A good name is better than a good comment
because it will be seen everywhere the function is used.
    

void DeleteRegistry(RegistryKey* key);

void ReleaseRegistryHandle(RegistryKey* key);

/*The name DeleteRegistry() sounds like a dangerous function (it deletes the registry?!). The
comment “This doesn’t modify the actual registry” is trying to clear up the confusion.
    Instead, we could use a more self-documenting name like:*/

4.Put Yourself in the Reader’s Shoes
*struct Recorder {
    vector<float> data;
...
    void Clear() {
        vector<float>().swap(data); // Huh? Why not just data.clear()?
    }
};

//it turns out that this is the only way to force a vector to
//truly relinquish its memory to the memory allocator

void Clear() {

    // Force vector to relinquish its memory (look up "STL swap trick")
    vector<float>().swap(data);
}
*};

1. Break Code into Paragraphs

var euclidean_norm = function (v)
{

/*# Import the user's email contacts, and match them to users in our system.
# Then display a list of those users that he/she isn't already friends with.*/

    def suggest_new_friends(user, email_password):

    friends = user.friends()
    friend_emails = set(f.email for f in friends)
    contacts = import_contacts(user.email, email_password)
    contact_emails = set(c.email for c in contacts)
    non_friend_emails = contact_emails - friend_emails
    suggested_friends = User.objects.select(email__in=non_friend_emails)
    display['user'] = user
    display['friends'] = friends
    display['suggested_friends'] = suggested_friends

return render("suggested_friends.html", display)
}

var euclidean_norm = function (v)
{

    //# Get the user's friends' email addresses.
    friends = user.friends()
    friend_emails = set(f.email for f in friends)

    //# Import all email addresses from this user's email account.
    contacts = import_contacts(user.email, email_password)
    contact_emails = set(c.email for c in contacts)

   // # Find matching users that they aren't already friends with.
    non_friend_emails = contact_emails - friend_emails
    suggested_friends = User.objects.select(email__in=non_friend_emails)

   // # Display these lists on the page.
    display['user'] = user
    display['friends'] = friends
    display['suggested_friends'] = suggested_friends

    return render("suggested_friends.html", display)
}

2. Organize Declarations into Blocks

class FrontendServer {
    public:
        FrontendServer();
    void ViewProfile(HttpRequest* request);
    void OpenDatabase(string location, string user);
    void SaveProfile(HttpRequest* request);
    string ExtractQueryParam(HttpRequest* request, string param);
    void ReplyOK(HttpRequest* request, string html);
    void FindFriends(HttpRequest* request);
    void ReplyNotFound(HttpRequest* request, string error);
    void CloseDatabase(string location);
    ~FrontendServer();
};

class FrontendServer {
    public:
        FrontendServer();
    ~FrontendServer();
    // Handlers
    void ViewProfile(HttpRequest* request);
    void SaveProfile(HttpRequest* request);
    void FindFriends(HttpRequest* request);
    // Request/Reply Utilities
    string ExtractQueryParam(HttpRequest* request, string param);
    void ReplyOK(HttpRequest* request, string html);
    void ReplyNotFound(HttpRequest* request, string error);
    // Database Helpers
    void OpenDatabase(string location, string user);
    void CloseDatabase(string location);
};

3.Rearrange Line Breaks to Be Consistent and Compact

public class PerformanceTester {
    public static final TcpConnectionSimulator wifi = new TcpConnectionSimulator(
        500, /* Kbps */
        80, /* millisecs latency */
        200, /* jitter */
        1 /* packet loss % */);
    public static final TcpConnectionSimulator t3_fiber =  new TcpConnectionSimulator(
            45000, /* Kbps */
            10, /* millisecs latency */
            0, /* jitter */
            0 /* packet loss % */);
    public static final TcpConnectionSimulator cell = new TcpConnectionSimulator(
        100, /* Kbps */
        400, /* millisecs latency */
        250, /* jitter */
        5 /* packet loss % */);
}

public class PerformanceTester {
    public static final TcpConnectionSimulator wifi =
        new TcpConnectionSimulator(
            500,    /* Kbps */
            80,     /* millisecs latency */
            200,    /* jitter */
            1       /* packet loss % */);
    public static final TcpConnectionSimulator t3_fiber =
        new TcpConnectionSimulator(
            45000,  /* Kbps */
            10,     /* millisecs latency */
            0,      /* jitter */
            0       /* packet loss % */);
    public static final TcpConnectionSimulator cell =
        new TcpConnectionSimulator(
            100,    /* Kbps */
            400,    /* millisecs latency */
            250,    /* jitter */
            5       /* packet loss % */);
}

public class PerformanceTester {
// TcpConnectionSimulator(throughput, latency, jitter, packet_loss)
                        // [Kbps] [ms] [ms] [percent]

    public static final TcpConnectionSimulator wifi =
        new TcpConnectionSimulator(500, 80, 200, 1);
    public static final TcpConnectionSimulator t3_fiber =
        new TcpConnectionSimulator(45000, 10, 0, 0);
    public static final TcpConnectionSimulator cell =
        new TcpConnectionSimulator(100, 400, 250, 5);
}

1.Matching Expectations of Users

var ShrinkList = function (list, max_size) {

    while (list.size() > max_size) {
        FreeNode(list.back());
        list.pop_back();
    }

/*    The “bug” is that the author didn’t know that list.size() is an O(n) operation—it counts
    through the linked list node by node, instead of just returning a precalculated count, which
    makes ShrinkList() an O(n2) operation.*/

    //Had size() been named countSize() or countElements(), the same mistake would be less likely.
    while (list.countSize() > max_size) {
        FreeNode(list.back());
        list.pop_back();
    }

    return 0;

};

2.Prefer min and max for Limits

var euclidean_norm = function (v) {

    CART_TOO_BIG_LIMIT = 10
    if (shopping_cart.num_items() >= CART_TOO_BIG_LIMIT)
        Error("Too many items in cart.")

/*    A D V I C E
    The clearest way to name a limit is to put max_ or min_ in front of the thing being
    limited.*/

    MAX_ITEMS_IN_CART = 10
    if (shopping_cart.num_items() > MAX_ITEMS_IN_CART)
        Error("Too many items in cart.")

/*    print integer_range(start=2, stop=4)
      set.PrintKeys(first="Bart", last="Maggie")
    # Does this print [2,3] or [2,3,4] (or something else)?*/

    return 0;

};

특정한 단어 고르기 - 구체적인 단어를 선택하자. 

    send - deliver, dispatch, announce, distribute, route 

    find - search, extract, locate, recover

    start - launch, create, begin, open

    make - create, set up, build, generate, compose, add, new

1.Avoid Generic Names Like tmp and retval

var euclidean_norm = function (v) {

    var retval = 0.0;  //에 실행된 명령들이 제대로 동작했느냐를 담아두는 변수라고
    var sum_squares = 0.0;
    for (var i = 0; i < v.length; i += 1)
    {
        retval += v[i] * v[i];
        sum_squares += v[i]; // Where's the "square" that we're summing? Bug!
    }

    return Math.sqrt(retval);
};

*만약 변수명이 sum_squares 였다면 다음 처럼 버그는 더 몇백하게 드러날 것이다. 

 sum_squares += v[i]; // 더해야 하는 '제곱'은 어디에 있다는 말인가? 버그다.  

*temp라는 이름은 대상이 짧게 임시적으로만 존재하고 , 임시적 존재 재체가 변수의 가장 중요한 용도일때 한해서 사용

 Swap 함수

  if (right, left) {

tmp = right; 

right = left;

left = tmp

}

2.Loop Iterators

var euclidean_norm = function (v) {

    for (var i = 0; i < clubs.size(); i++)
    {
        for (var j = 0; j < clubs[i].members.size(); j++)
        {
            for (var k = 0; k < users.size(); k++)
            {
                if (clubs[i].members[k] == users[j]) ;
            }

        }
    }

     //When used correctly, the first letter of the index would match the first letter of the array
    for (var ci = 0; ci < clubs.size(); ci++)
    {
        for (var mi = 0; ci < clubs[ci].members.size(); mi++)
        {
            for (var ui = 0; ui < users.size(); ui++)
            {
                if (clubs[ci].members[mi] == users[ui]) ;
            }

        }
    }

    return 0;

};

3.Values with Units

var euclidean_norm = function (v) {

    var start = (new Date()).getTime(); // top of the page
    var elapsed = (new Date()).getTime() - start; // bottom of the page
    document.writeln("Load time was: " + elapsed + " seconds");

    //By appending _ms to our variables, we can make everything more explicit:
    var start_ms = (new Date()).getTime(); // top of the page
    var elapsed_ms = (new Date()).getTime() - start_ms; // bottom of the
    document.writeln("Load time was: " + elapsed_ms / 1000 + " seconds");

    return 0;

};

/*    Function parameter Renaming parameter to encode units
    Start(int delay ) delay → delay_secs
    CreateCache(int size ) size → size_mb
    ThrottleDownload(float limit) limit → max_kbps
    Rotate(float angle) angle → degrees_cw*/

   password => plaintext_password    

   comment => unescaped_comment

   html => html_utf8

   data => data_urlenc