Writing Beautiful Code

Vimal JosephTechnical Architect

Aesthetics of code and its relevance

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How do you define beauty?

Image Courtesy: Indian People Collage by Jamie Furlong

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How do you define beauty?

Guernica by Picasso

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How do you define beauty?

Starry Night by VanGogh

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How do you define beauty?

Water lilies, Nymphaea nouchali, Okavango Delta, Botswana

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How do you define beauty?

Each of us will have a different opinion on what is beautiful

Beauty is relative

Beauty is a perception

Beauty is structure

Beauty is consistency

Beauty is some thing that please our senses

You may have some thing else to say...

Is it possible to measure beauty? Can you identify anything common for beautiful things?

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How do you define beauty?

BMW M5

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How do you define beauty?

BMW M5

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How do you define beauty?

Microprocessor

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How do you define beauty? /* match: search for regexp anywhere in text */ int match(char *regexp, char *text) { if (regexp[0] == '^') return matchhere(regexp+1, text); do { /* must look even if string is empty */ if (matchhere(regexp, text)) return 1; } while (*text++ != '\0'); return 0;}

/* matchhere: search for regexp at beginning of text */int matchhere(char *regexp, char *text) { if (regexp[0] == '\0') return 1; if (regexp[1] == '*') return matchstar(regexp[0], regexp+2, text); if (regexp[0] == '$' && regexp[1] == '\0') return *text == '\0'; if (*text!='\0' && (regexp[0]=='.' || regexp[0]==*text)) return matchhere(regexp+1, text+1); return 0;}

/* matchstar: search for c*regexp at beginning of text */int matchstar(int c, char *regexp, char *text) { do { /* a * matches zero or more instances */ if (matchhere(regexp, text)) return 1; } while (*text != '\0' && (*text++ == c || c == '.')); return 0;}

http://www.cs.princeton.edu/courses/archive/spr09/cos333/beautiful.html

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Beauty

I have a friend who's an artist and has sometimes taken a view which I don't agree with very well. He'll hold up a flower and say "look how beautiful it is," and I'll agree. Then he says "I as an artist can see how beautiful this is but you as a scientist take this all apart and it becomes a dull thing," and I think that he's kind of nutty. First of all, the beauty that he sees is available to other people and to me too, I believe. Although I may not be quite as refined aesthetically as he is ... I can appreciate the beauty of a flower.

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Beauty (contd...)

At the same time, I see much more about the flower than he sees. I could imagine the cells in there, the complicated actions inside, which also have a beauty. I mean it's not just beauty at this dimension, at one centimeter; there's also beauty at smaller dimensions, the inner structure, also the processes. The fact that the colors in the flower evolved in order to attract insects to pollinate it is interesting; it means that insects can see the color. It adds a question: does this aesthetic sense also exist in the lower forms? Why is it aesthetic? All kinds of interesting questions which the science knowledge only adds to the excitement, the mystery and the awe of a flower. It only adds. I don't understand how it subtracts.

– Richard P. Feynman

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Appreciating beauty...Context

Familiarity

Curiosity

Quest for Knowledge

Compassion

Ever thought about the audience of your code?

Code is also written for humans to read, not only for computers to execute.

– Erkki Lindpere

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Rules that make things beautiful

Proportions

Integrity

Clarity

Standards

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The Zen of Python

Beautiful is better than ugly.

Explicit is better than implicit.

Simple is better than complex.

Complex is better than complicated.

Flat is better than nested.

Sparse is better than dense.

Readability counts.

Special cases aren't special enough to break the rules.

Although practicality beats purity.

Errors should never pass silently.

Unless explicitly silenced.

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The Zen of Python (contd...)

In the face of ambiguity, refuse the temptation to guess.

There should be one-- and preferably only one --obvious way to do it.

Although that way may not be obvious at first unless you're Dutch.

Now is better than never.

Although never is often better than *right* now.

If the implementation is hard to explain, it's a bad idea.

If the implementation is easy to explain, it may be a good idea.

Namespaces are one honking great idea -- let's do more of those!

by Tim Peters Example: http://bit.ly/dQzuxW

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What they said about beautiful code?

Beautiful code is likely to be simple -- clear and easy to understand. Beautiful code is likely to be compact -- just enough code to do the job and no more -- but not cryptic, to the point where it cannot be understood. Beautiful code may well be general, solving a broad class of problems in a uniform way. One might even describe it as elegant, showing good taste and refinement.

- Brian Kernighan

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What they said about beautiful code? (contd...)

I like my code to be elegant and efficient. The logic should be straightforward to make it hard for bugs to hide, the dependencies minimal to ease maintenance, error handling complete according to an articulated strategy, and performance close to optimal so as not to tempt people to make the code messy with unprincipled optimizations. Clean code does one thing well.

- Bjarne Stroustrup, inventor of C++

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Clean the code

Always leave the campground cleaner than you found it.

- The Boy Scout Rule

Developers often get anxious to move on to the next feature and forget to clean up the trash that they have left lying around: forgetting to clean

Duplicated code

Poorly named functions and variables

Huge functions

Magic numbers

Inappropriate combinations of differing levels of abstraction

Tight coupling

and the list goes on...

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Things to be taken care of...

Names

Expressions and Statements

Consistency and Idioms

Magic numbers

Comments

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Bad Code, Good Codeif (($country == SING) || ($country == BRNI) || ($country == POL) || ($country == ITALY)) { // If the country is Singapore, Brunei or Poland then the current   // time is the answer time rather than the off hook time. // Reset answer time and set day of week. ...

What relationship links Singapore, Brunei, Poland and Italy? Why isn't Italy mention in the comment?

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Bad Code, Good Code - Namesdefine(“ONE”, 1);define(“TEN”, 10);define(“TWENTY”, 20);

define(“INPUT_MODE”, 1);define(“INPUT_BUFSIZE”, 10);define(“OUTPUT_BUFSIZE”, 20);

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Bad Code, Good Code - Namesfor ($the_element_index = 0; $the_element_index < $number_of_elements;  the_element_index++) {  $element_array[$the_element_index] = $the_element_index;}

for ($i = 0, $i < $nelems; $i++) {  elem[$i] = $i;}

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Bad Code, Good Code - Namesclass UserQueue { public $no_of_elements_in_q = 10; public $front_of_the_queue = 0; public $queue_capacity = 20;

 public function no_of_users_in_queue() {    ... }}queue = new UserQueue;queue­>queue_capacity

$queue = new UserQueue;$queue­>capacity++;$n = $queue­>nusers();

class UserQueue { public $nitems = 10; public $front = 0; public $capacity = 20;

 public function nusers() {    ... }}

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Bad Code, Good Code - Namesif (checkprime($n)) {  …}

if (isprime($n)) {  …}

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Bad Code, Good Code - Names

function intable($obj) {  $j = $this­>get_index($obj);//return a value between 0 and   //ntable – 1 if it find the string, and returns ntable if not.  return ($j == $ntable);}

­­

function smaller($s, $t) {  if (strcmp($s, $t) < 1) {    return 1;  }  else {    return 0;  }}

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Bad Code, Good Code - Expressionsif (!($block_id < $actblks) || !($block_id >= $unblocks)) {  …}

if (block_id >= actblks) || block_id < unblocks)) {  …}

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Bad Code, Good Code - Expressions$leap_yr = $y % 4 == 0 && $y % 100 != 0 || $y % 400 == 0;

$leap_yr = (($y % 4 == 0) && ($y % 100 != 0)) || ($y % 400 == 0);

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Bad Code, Good Code - Expressions$x += ($xp = (2 * $k < ($n ­ $m) ? $c[$k + 1] : $d[$k ­ 1]));

if (2 * $k < ($n ­ $m)) {  $xp = $c[$k + 1];}else {  $xp = $d[$k ­ 1];}$x += $xp;

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Bad Code, Good Code - Expressions$length = ($length < BUFSIZE) ? $length : BUFSIZE;

if ($length > BUFSIZE) {  $length = BUFSIZE;}

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Bad Code, Good Code - Expressionsif ($month == FEB) {  if ($year % 4 == 0)    if ($day > 29)      $legal = FALSE;  else    if ($day > 28)      $legal = FALSE;}

if ($month == FEB) {  $nday = 28;  if ((($year % 4 == 0) && ($year % 100 != 0))     || $year % 400 == 0) {    $nday = 29;  }  if ($day > $nday) {    $legal = FALSE;  }}

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Bad Code, Good Code - Idioms$i = 0;while ($i <= $n­1)  $array[$i++] = 1.0;

–

for ($i = 0; $i < $n;)  $array[$i++] = 1.0;

–

for ($i = n; $i = $i ­ 1 >=0;)  $array[$i] = 1.0;

–

for ($i = 0; i < n; i++)  $array[$i] = 1.0;

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Bad Code, Good Code - Idiomsif (isset($f1) && isset($f2))  if (($fin = $fopen($f1, 'r')) != NULL)    if (($fout = fopen($f2, 'w')) != NULL) {      while (($c = getc(fin)) !== false)         fputs($c, $fout);       fclose($fin);       fclose($fout);    }    else      printf("Can't open output file %s\n", f2); else   printf("Can't open input file %s\n", f1);else  printf("Incorrect arguments");

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Bad Code, Good Code - Idioms

if (!isset($f1) || !isset($f2))  print 'Incorrect arguments';else if (($fin = $fopen($f1, 'r')) == NULL)  printf("Can't open input file %s\n", f1);else if (($fout = fopen($f2, 'w')) == NULL) {  printf("Can't open output file %s\n", f2);    fclose($fin);}else {  while (($c = fgetc($fin) !== false) {    fputs($c, $fout);  }  fclose($fin);  fclose($fout);}

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Bad Code, Good Code – Magic Numbers

/** * Print a histogram of letter frequencies on a * 24 lines by 80 columns screen */$fac = $lim / 20; //set scale factorif ($fac < 1)  $fac = 1;//generate histogramfor ($i = 0, $col = 0; $i < 27; $i++) {  $col += 3;  $k = 21 ­ ($let[$i] / $fac);  $star = ($let[$i] == 0) ? ' ' : "*";  for ($j = $k; $j < 22; $j++)    draw($j, $col, $star);}draw(23, 2, ' '); //Label x axisfor ($i = 'A'; $i <= 'Z'; $i++)  printf("%c ", $i);

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Bad Code, Good Code – Magic Numbers

define(“MINROW”, 1);                   // Top edgedefine(“MINCOL”, 1);                   // Left edgedefine(“MAXROW”, 24);                  // Bottom edge (<=)define(“MAXCOL”, 80);                  // Right edge (<=)define(“LABELROW”, 1);                 // Position of labelsdefine(“NLET”, 26);                    // Size of alphabetdefine(“HEIGHT”, MAXROW – 4);          // Height of barsdefine(“WIDTH”, (MAXCOL ­ 1) / NLET)   // Width of bars...

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Bad Code, Good Code – Magic Numbers (contd...)

...$fac = ($lim + HEIGHT ­ 1) / HEIGHT; // Set scale factorif ($fac < 1)  $fac = 1;//generate histogramfor ($i = 0; $i < NLET; $i++) {  if ($let[$i] == 0)    continue;  for ($j = HEIGHT ­ $let[$i] / $fac; $j < HEIGHT; $j++)    draw($j + 1 + LABELROW, ($i + 1) * WIDTH, '*');}draw(MAXROW ­ 1, MINCOL + 1, ' '); //Label x axisfor ($i = 'A'; $i <= 'Z'; $i++)  printf("%c ", $i);

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Bad Code, Good Code - Comments// defaultdefault:  break;// return SUCCESSreturn SUCCESS;

$zerocount++; //increment zero entry counter

$node­>total = $node­>number_received; // Initialize total to number_received

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Bad Code, Good Code - Comments// string comparison routine returns ­1 if s1 is// above s2 in an ascending order list, 0 if equal// 1 if s1 below s2function strcmp(s1, s2) {  …}

// strcmp: return < 0 if sl < s2, > 0 if s1 > s2, 0 if equalfunction strcmp(s1, s2) {  …}

if (n > MAX || n % 2 > 0) // test for even number

The comment is incomplete; the code actually tests for a even number or a number that is greater than MAX.

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Some food for thought...

Quality is not an act, it is a habitFirst, solve the problem. Then, write the code. — John Johnson

Incorrect documentation is often worse than no documentation. — Bertrand Meyer

Controlling complexity is the essence of computer programming. — Brian Kernighan

One of my most productive days was throwing away 1000 lines of code. — Ken Thompson

There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies and the other way is to make it so complicated that there are no obvious deficiencies. — C.A.R. Hoare, The 1980 ACM Turing Award Lecture

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ReferencesThe Practice of Programming - Brian Kernighan, Rob Pike

Code Complete 2ed. - Steve McConnell

A Regular Expression Matcher - http://bit.ly/1hAUGzh by Brian Kernighan

Clean Code - Robert C Martin

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