Created
August 3, 2014 09:11
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テイラー展開でsin, cos, tanを近似的に算出するscssの関数です。その過程で冪乗計算と階乗計算も行っています。
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@charset "utf-8"; | |
$pi: 3.14159265359; // 円周率 | |
$iter: 10; // テイラー展開時の項数(多いほど近似精度が高い) | |
/* 冪乗計算(乗数は整数のみ) | |
* | |
* $base: 冪乗される数 | |
* $exp : 冪乗する回数 | |
* | |
* @return: $baseの$exp乗 | |
* | |
* 例: $base=2, $exp=3 => @return=8 | |
*/ | |
@function pow($base, $exp){ | |
$value: $base; | |
@if $exp >= 1 { | |
@for $i from 1 through $exp { | |
$value: $value * $base; | |
} | |
} @else if $exp <= -1 { | |
@for $i from 1 through -$exp { | |
$value: $value / $base; | |
} | |
} @else { | |
$value: 1; | |
} | |
@return $value; | |
} | |
/* 階乗計算 | |
* | |
* $val: 階数 | |
* | |
* @return: $valの階乗 | |
* | |
* 例: $val=5 => @return=120 | |
*/ | |
@function fact($val){ | |
$value: 1; | |
@if $val > 0{ | |
@for $i from 1 through $val{ | |
$value: $value * $i; | |
} | |
} @else { | |
$value: 1; | |
} | |
@return $value; | |
} | |
/* 正弦(sin)計算 | |
* | |
* $angle: 角度(弧度法) | |
* $degrees: $angleが度数かどうか | |
* | |
* @return: sin($angle) | |
* | |
* 例: $angle=30, $degrees=true => @return=0.5 | |
*/ | |
@function sin($angle, $degrees: false) { | |
$sin: 0; | |
@if $degrees { | |
$angle: $angle / 180 * $pi; | |
} | |
@for $n from 0 through $iter - 1 { | |
$sin: $sin + (pow(-1, $n) / fact(2*$n + 1)) * pow($angle, 2*$n + 1); | |
} | |
@return $sin; | |
} | |
/* 余弦(cos)計算 | |
* | |
* $angle: 角度(弧度法) | |
* $degrees: $angleが度数かどうか | |
* | |
* @return: cos($angle) | |
* | |
* 例: $angle=60, $degrees=true => @return=0.5 | |
*/ | |
@function cos($angle, $degrees: false){ | |
$cos: 0; | |
@if $degrees{ | |
$angle: $angle / 180 * $pi; | |
} | |
@for $n from 0 through $iter - 1 { | |
$cos: $cos + (pow(-1, $n) / fact(2*$n)) * pow($angle, 2*$n); | |
} | |
@return $cos; | |
} | |
/* 正接(tan)計算 | |
* | |
* $angle: 角度(弧度法) | |
* $degrees: $angleが度数かどうか | |
* | |
* @return: tan($angle) | |
* | |
* 例: $angle=45, $degrees=true => @return=1 | |
*/ | |
@function tan($angle, $degrees: false){ | |
@if $degrees{ | |
$angle: $angle / 180 * $pi; | |
} | |
$tan: sin($angle) / cos($angle); // 近似値なので無限大にはならない | |
@return $tan | |
} |
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