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α-wwwiki :: history/map_reduce/20130717-101920.txt

editor : alpha [82.251.234.161] 2013/07/17 10:19:20
_h1 map & reduce
_p Using the "define" lambdatalk operator to build the functions "map" and "reduce".
{pre
1) define and call the function square :
°°{define square (x) return x*x }°° -> {define square (x) return x*x }
°°{square 12}°° -> {square 12}

2) define and call the function serie
°°{define serie (n)
  for (var str='', i=0; i< n; i++)  
    str += i + ' ';
  return str;
}°° -> {define serie (n)
  for (var str='', i=0; i< n; i++)  
    str += i + ' ';
  return str;
}

°°{serie 11}°° -> {serie 11}

3) define and call the function map applying square to the previous serie
°°{define map (func)
  for (var str='', i=1; i< arguments.length; i++)  
    str += '{'+func+' '+arguments[i]+'}' + ' ';
  return str;
}°° -> {define map (func)
  for (var str='', i=1; i< arguments.length; i++)  
    str += '{'+func+' '+arguments[i]+'}' + ' ';
  return str;
}

°°{map square {serie 11}}°° -> {map square {serie 11}}

4) define and call the function reduce applying '+' to the previous serie
°°{define reduce (func)
  var args = [].slice.call(arguments).slice(1).join(' ');
  return '{'+func+' '+args+'}';
}°° -> {define reduce (func)
  var args = [].slice.call(arguments).slice(1).join(' ');
  return '{'+func+' '+args+'}';
}

°°{reduce + {map square {serie 11}}}°° -> {reduce + {map square {serie 11}}}

}

_h3 E : {{lambda () return Math.E}}
{pre
°°{define expK (n) 
  function fac(n) { return (n< 1)? 1 : n*fac(n-1) }
  return 1/fac(n)
}°° -> {define expK (n) 
  function fac(n) { return (n< 1)? 1 : n*fac(n-1) }
  return 1/fac(n)
}

°°{reduce + {map expK {serie 1}}}°° -> {reduce + {map expK {serie 1}}}
°°{reduce + {map expK {serie 2}}}°° -> {reduce + {map expK {serie 2}}}
°°{reduce + {map expK {serie 3}}}°° -> {reduce + {map expK {serie 3}}}
°°{reduce + {map expK {serie 4}}}°° -> {reduce + {map expK {serie 4}}}
°°{reduce + {map expK {serie 5}}}°° -> {reduce + {map expK {serie 5}}}
°°{reduce + {map expK {serie 6}}}°° -> {reduce + {map expK {serie 6}}}
°°{reduce + {map expK {serie 7}}}°° -> {reduce + {map expK {serie 7}}}
°°{reduce + {map expK {serie 8}}}°° -> {reduce + {map expK {serie 8}}}
°°{reduce + {map expK {serie 9}}}°° -> {reduce + {map expK {serie 9}}}
°°{reduce + {map expK {serie 10}}}°° -> {reduce + {map expK {serie 10}}}
...
°°{reduce + {map expK {serie 18}}}°° -> {reduce + {map expK {serie 18}}}
...
to be compared to the javascript Math value of E

}

_h3 links
_ul http://jsmapreduce.com/