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[Raku] Range sum method

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Kang-min Liu

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May 28, 2020, 10:27:37 AM5/28/20
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https://github.com/rakudo/rakudo/blob/master/src/core.c/Range.pm6#L630

昨天正好意識到，以 `+` 算符去將一串數字 1..$n 加總起來時：

my $sum = [+] 1..$n;

其實不必做 n-1 次加法，而是有個公式解： n(n+1)/2

稍後看了一下 Rakudo 源碼，發現此公式解已經實做在其中了。

😎 Cool


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