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α-wwwiki :: history/map/20130609-071617.txt

editor : alpha [37.160.6.34] 2013/06/09 07:16:17
_h1 serie & map
_p Two useful functions of lambdatalk : serie and map :
_ul °°{serie start end}°° generates a serie of integer from start to end with increment 1. Todo : let the increment be choosen different then one.
_ul °°{map func serie}°° applies a function (one argument) to a serie of values. It is an equivalent to the iterative structure {u for (var i=start; i< end; i++) func(i);} . The function can be a lambdatalk core function, a function defined in the page (or in another by [[include]]) or a lambda function.

_h3 1) serie
{pre {@ style="white-space:pre-wrap;"}
°°{serie 1 20}°° 
-> {serie 1 20}
}

_h3 2) map a function on a serie
{pre {@ style="white-space:pre-wrap;"}
1) using a predefined function
°°{define sqr (x) return x*x; } °°-> {define sqr (x) return x*x; }
°°{map sqr {serie 1 20}}°° ->
{map sqr {serie 1 20}}

2) using a lambda function
°°{map {lambda (x) return x*x; } {serie 1 20}}°° -> 
{map {lambda (x) return x*x; } {serie 1 20}}

3) another one
°°{map {lambda (x) return Math.sqrt(x);} {serie 1 36}}°° ->
{map {lambda (x) return Math.sqrt(x);} {serie 1 36}}

}

_h3 another one

{define foo (x) °°

function fac (n) { return (n< 1)? 1 : n*fac(n-1); }

var css = "font:bold "+(x/3)+"em courier new;"
     + "background:rgb("+(25*x)+","+(250-25*x)+",0);"
     + "transform:rotate("+x+"deg);"
     + "-webkit-transform:rotate("+x+"deg);"
     + "border:1px solid white;"
     + "text-align:center;";
   return '{div {@ style="'+css+'"}'+x+'! = '+fac(x)+'}';

°°}

_p °°{map foo 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1}°° ->
{map foo 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 1}