Programming in handstand

Programozz kézenállva!

Magyar Attila (@athoshun)PHP Meetup, 2013. 02. 26.

FizzBuzz

Write a program that iterates through the numbers between 1 and 100:

For multiples of 3 print "Fizz" For multiples of 5 print "Buzz" For numbers which are multiples of both 3 and 5

print "FizzBuzz" For others, print the number itself

FizzBuzz

Write a program that iterates through the numbers between 1 and 100:

For multiples of 3 print "Fizz" For multiples of 5 print "Buzz" For numbers which are multiples of both 3 and 5

print "FizzBuzz" For others, print the number itself

1, 2, Fizz, 4, Buzz, Fizz, 7, 8, Fizz, Buzz,11, Fizz, 13, 14, FizzBuzz, 16, 17, Fizz, 19,Buzz, Fizz, 22, 23, Fizz, Buzz, 26, Fizz, 28,29, FizzBuzz, ...

Triviális megoldás

for ($i = 1; $i <= 100; ++$i) { if ($i % 3 == 0) print "Fizz"; if ($i % 5 == 0) print "Buzz"; if ($i % 3 && $i % 5) print $i; print ", ";}

Ciklus nélkül!

Ciklus nélkül!

Ciklus nélkül!

function fizzbuzz($i = 1){ if ($i > 100) return;

if ($i % 3 == 0) print "Fizz"; if ($i % 5 == 0) print "Buzz"; if ($i % 3 && $i % 5) print $i; print ", ";

fizzbuzz($i + 1);}

Ciklus nélkül!

function fizzbuzz($i = 1){ if ($i > 100) return;

if ($i % 3 == 0) print "Fizz"; if ($i % 5 == 0) print "Buzz"; if ($i % 3 && $i % 5) print $i; print ", ";

fizzbuzz($i + 1);}

PHP Fatal error: Maximumfunction nesting levelof '100' Reached, aborting!

Ciklus nélkül!

Ciklus nélkül!

Ciklus nélkül!

$fizzbuzz = function ($i) { if ($i % 3 == 0) print "Fizz"; if ($i % 5 == 0) print "Buzz"; if ($i % 3 && $i % 5) print $i; print ", ";};

array_map($fizzbuzz, range(1, 100));

Elágazás nélkül!


$id = function ($x) { return $x; };



$fizz = function ($x) { return "Fizz"; };$buzz = function ($x) { return "Buzz"; };$fizzbuzz = function ($x) { return "FizzBuzz";};


$functions = array( $fizzbuzz, $id, $id, $fizz, $id, $buzz, $fizz, $id, $id, $fizz, $buzz, $id, $fizz, $id, $id);array_map( function ($x) use ($functions) { print $functions[$x % 15]($x) . ", "; }, range(1, 100));

Redundancia



Redundancia



Redundancia



function const_($const) { return function ($x) use ($const) { return $const; };}

Redundancia


$fizz = const_("Fizz");$buzz = const_("Buzz");$fizzbuzz = const_("FizzBuzz");

function const_($const) { return function ($x) use ($const) { return $const; };}

Redundancia



DON'T REPEAT YOURSELF!!!

Redundancia



function concat($f, $g){ return function ($x) use ($f, $g) { return $f($x) . $g($x); };}

Redundancia


$fizz = const_("Fizz");$buzz = const_("Buzz");$fizzbuzz = concat($fizz, $buzz);

function concat($f, $g){ return function ($x) use ($f, $g) { return $f($x) . $g($x); };}

$id = function ($x) { return $x; };$fizz = const_("Fizz");$buzz = const_("Buzz");$fizzbuzz = concat($fizz, $buzz);$functions = array( $fizzbuzz, $id, $id, $fizz, $id, $buzz, $fizz, $id, $id, $fizz, $buzz, $id, $fizz, $id, $id);array_map( function ($x) use ($functions) { print $functions[$x % 15]($x) . ", "; }, range(1, 100));


3 többszörösei

function multiples_of_3(){ return array_map( function ($x) { return $x * 3; } range(1, 10) );}

var_dump( multiples_of_3() );// 3, 6, 9, 12, 15, 18, 21, 24, 27, 30

3 többszörösei

function multiples_of_3(){ return array_map( function ($x) { return $x * 3; } range(1, 10) );}

var_dump( multiples_of_3() );// 3, 6, 9, 12, 15, 18, 21, 24, 27, 30

3 többszörösei

function multiples_of_3(){ return array_map( multiply_by_3(), range(1, 10) );}function multiply_by_3(){ return function ($x) { return $x * 3; }}

3 többszörösei

function multiples_of_3(){ return array_map( multiply_by_3(), range(1, 10) );}function multiply_by_3(){ return function ($x) { return $x * 3; }}

3 többszörösei

function multiples_of_3(){ return array_map( multiply_by(3), range(1, 10) );}function multiply_by($n){ return function ($x) use ($n) { return $x * $n; }}

3 többszörösei

function multiples_of($n){ return array_map( multiply_by($n), range(1, 10) );}function multiply_by($n){ return function ($x) use ($n) { return $x * $n; }}

3 többszörösei

function multiples_of($n){ return array_map( multiply_by($n), range(1, 10) );}

var_dump( multiples_of(5) );// 5, 10, 15, 20, 25, 30, 35, 40, 45, 50

A 3 első öt többszöröse

function take($n, array $from){ return array_slice($from, 0, $n);}

A 3 első öt többszöröse

function take($n, array $from){ return array_slice($from, 0, $n);}

var_dump( multiples_of(3) );// 3, 6, 9, 12, 15, 18, 21, 24, 27, 30

var_dump( take(5, multiples_of(3)) );// 3, 6, 9, 12, 15

A többi szám

function subtract(array $from, array $what){ return array_diff($from, $what);}

A többi szám

function subtract(array $from, array $what){ return array_diff($from, $what);}

var_dump( subtract( range(1, 15), take(5, multiples_of(3)) ));

// 1, 2, 4, 5, 7, 8, 10, 11, 13, 14

4 halmaz, modulo 15

$multiples_of_3 = take(4, multiples_of(3));$multiples_of_5 = take(2, multiples_of(5));$multiples_of_both = array(0);$others = subtract( range(1, 14), array_merge($multiples_of_3, $multiples_of_5));

4 halmaz, modulo 15


var_dump( array_merge( $multiples_of_3, $multiples_of_5, $multiples_of_both, $others ));// 3, 6, 9, 12, 5, 10, 0, 1, 2, 4, 7, 8, 11, 13, 14

Érték → tömb

function repeat($value, $times){ return array_fill(0, $times, $value);}

var_dump( repeat(42, 4) );

// 42, 42, 42, 42

Érték → tömb

function repeat($value, $times){ return array_fill(0, $times, $value);}

var_dump( repeat(function () {}, 4) );

// object(Closure)#1 (0) {},// object(Closure)#1 (0) {},// object(Closure)#1 (0) {},// object(Closure)#1 (0) {}

( Tömb, tömb ) → tömb

( Tömb, tömb ) → tömb

$keys = array(42, 43, 44);$values = array( "Fortytwo", "Fortythree", "Fortyfour");

var_export(array_combine($keys, $values));

// array (// 42 => 'Fortytwo',// 43 => 'Fortythree',// 44 => 'Fortyfour',// )

( Tömb, függvény ) → tömb

function for_all(array $values, $function) { return array_combine( $values, repeat($function, count($values)) );}

( Tömb, függvény ) → tömb

function for_all(array $values, $function) { return array_combine( $values, repeat($function, count($values)) );}

$items = array(42, 43, 44);$do_something = function () {};var_dump( for_all($items, $do_something) );

// array(3) {// [42] => object(Closure)#1 (0) {}// [43] => object(Closure)#1 (0) {}// [44] => object(Closure)#1 (0) {}// }

Hol is tartunk?


Hol is tartunk?


$functions = for_all($multiples_of_3, $fizz) + for_all($multiples_of_5, $buzz) + for_all($multiples_of_both, $fizzbuzz) + for_all($others, $id);

Függvény → kiírás

function print_($function){ return function ($x) use ($function) { print $function($x); };}

Alakul...

$functions = for_all($multiples_of_3, print_($fizz)) + for_all($multiples_of_5, print_($buzz)) + for_all($multiples_of_both, print_($fizzbuzz)) + for_all($others, print_($id));

array_map( function ($x) use ($functions) { print $functions[$x % 15]($x); print ", "; }, range(1, 100));

Alakul...

$functions = for_all($multiples_of_3, print_($fizz)) + for_all($multiples_of_5, print_($buzz)) + for_all($multiples_of_both, print_($fizzbuzz)) + for_all($others, print_($id));

array_map( function ($x) use ($functions) { $functions[$x % 15]($x); print ", "; }, range(1, 100));

Alakul...

$them = $id;

$functions = for_all($multiples_of_3, print_($fizz)) + for_all($multiples_of_5, print_($buzz)) + for_all($multiples_of_both, print_($fizzbuzz)) + for_all($others, print_($them));

array_map( function ($x) use ($functions) { $functions[$x % 15]($x); print ", "; }, range(1, 100));

A végeredmény

for_all($multiples_of_3, print_($fizz)) + for_all($multiples_of_5, print_($buzz)) + for_all($multiples_of_both, print_($fizzbuzz)) + for_all($others, print_($them));

A végeredmény

for_all($multiples_of_3, print_($fizz)) + for_all($multiples_of_5, print_($buzz)) + for_all($multiples_of_both, print_($fizzbuzz)) + for_all($others, print_($them));

A végeredmény

for all multiples of 3 print fizz for all multiples of 5 print buzz for all multiples of both print fizzbuzz for all others, print them

DON'T TRY THIS AT HOME!

Memória pazarló Lassú

TRY THIS AT HOME!

Más szemlélet Mellékhatások nélkül → determinisztikus Trükkök:

Lazy evaluation (lazy iterators) Cache-elés Tail call optimization

Többszálúság? (Párhuzamos algoritmusok, skálázás)

Köszönöm a figyelmet!

Másik változat :-)

function fizzbuzz(){ $functions = array( const_("FizzBuzz"), const_("Buzz"), const_("Fizz"), id() ); array_map( function ($x) use ($functions) { print $functions[ !!($x % 3) + 2 * !!($x % 5) ]($x) . ", "; }, range(1, 100) );}

Harmadik változat :-)

function fizzbuzz(){ array_map( function ($x) { print array_reduce( array( when(divisable_by(3), append(const_("Fizz"))), when(divisable_by(5), append(const_("Buzz"))), when(neither(), append(id())), ), apply_filter_with($x), ”” ) . ", "; }, range(1, 100) );}

Technology

Programming in handstand