Let's Play Code Golf

[Steve Sobel via Digitalmars-d]

On Monday, 23 February 2015 at 21:30:51 UTC, Steven Schveighoffer 
wrote:
> 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

It can get down to 155 using ranges, but those imports really are 
killer.

void main(){import 
std.algorithm,std.conv,std.range,std.stdio;foreach(n;stdin.byLine.drop(1))writefln("%.15f",iota(n.to!int).map!"(-1.0)^^a/(2*a+1)".sum);}