Let's Play Code Golf

[Steven Schveighoffer via Digitalmars-d]

On 2/23/15 3:21 PM, Charles wrote:
> For the uninitiated, Code Golf is producing the correct answer to a
> question with minimal syntax (whitespace included). I found a couple
> questions on HackerRank, which allows D compilation. So far there's only
> two entries for D (mine and another) for the first problem.
>
> Here's the problem:
>
> In Calculus, the Leibniz formula for π is given by:
>
> 1 - 1/3 + 1/5 - 1/7 + 1/9 - ... = pi/4
>
> You will be given an integer n. Your task is to print the summation of
> the Leibniz formula up to the nth term of the series correct to 15
> decimal places.
>
> Input Format
>
> The first line contains the number of test cases (T) which is less than
> 100. Each additional line is a test case for a positive integer value
> (p) less than 10^7.
>
> Sample Input
>
> 2
> 10
> 20
>
> Output Format
>
> Output T lines, with each line containing the summation up to nth term.
>
> Sample Output
>
> 0.760459904732351
> 0.772905951666960
>
> Scoring
>
> This is a code golf question. The goal is to write a solution with as
> little code as possible. A correct submission with a source code of X
> characters will receive the following score:
>
> maxScore * (300 - X)/300
>
> Any correct code longer than 300 characters will receive a score of
> maxScore * 0.001.
> MaxScore is the maximum score attainable for the problem.
> Note that whitespace is also treated as a character.
>
>
>
>
>
> My solution (150 characters, 15 points):
>
>      void main(){import std.stdio;int t,n;readf("
> %d",&t);while(t--){readf(" %d",&n);real
> a=0,i=0;for(;i<n;i++)a+=(i%2?-1:1)/(i+i+1);writefln("%.15f",a);}}
>
> Link to problem site: https://www.hackerrank.com/challenges/leibniz
>
> Anyone care to do better? :)


I didn't beat your score, but I did it with ranges (full character count 
was 174):

stdin.readln();
foreach(x; stdin.byLine)
     writefln("%0.15f", map!(a => 
(a&1?-1:1)/(2.0*a+1))(iota(x.to!int)).sum);

I think if I didn't have to import so many things, I would have done 
much better :)

-Steve