# Reducing Leibniz perl code in characters

This Perl code is supposed to calculate the Leibniz formula. The original problem is here.

The input format is:

T
<T test cases, each on their own line>


Each test case is a number < 10^7. The output format should be the same, minus the first line.

For example, an input:

2
10
20


And for output:

0.760459904732351
0.77290595166696


My first solutions, at 62 and 61 characters respectively.

for(1..<>){$s=0;map{$s+=($_&1||-1)/(2*$_-1)}1..<>;print"$s\n"} for(1..<>){$s=0;$s+=($_&1||-1)/(2*$_-1)for 1..<>;print"$s\n"}


Edit: The best solution so far is 53 characters, by @teebee:

<>;print${\map$a-=(-1)**$_/(2*$_-1),1..$_},$a=$/for<>  • possible duplicate of Calculate pi to 5 decimals Commented Feb 5, 2013 at 7:49 • Why post the same question on two sites? I feel like it's either help or a puzzle, but not both. And as a puzzle it needs a puzzle-type (code-golf, coding-challenge) and objective winning criteria. Commented Feb 5, 2013 at 8:06 • I was recommended that this question belongs here more then stackoverflow so posted here. Commented Feb 5, 2013 at 8:16 ## 2 Answers # Perl 53 bytes You can save two more strokes: <>;print${\map$a-=(-1)**$_/(2*$_-1),1..$_},$a=$/for<>

• Very clever. One would expect \map... to return a single array reference, and not a list of scalar references. Commented Jun 10, 2013 at 9:28

## Perl 55 bytes

<>;map($s-=(-1)**$_/(2*$_-1),1..$_),$s=!print$s,$/for<>  Without using any Perl non-standard features (such as say). 3 bytes are wasted removing the first value from the input. Sample usage: in.dat 2 10 20  $ perl leibniz.pl < in.dat
0.760459904732351
0.77290595166696


## Alternative, also 55 bytes

map{$s-=(-1)**$_/($_*2-1)for 1..<>;$s=!print$s,$/}1..<>


The alternative may be run interactively, without requiring an input file. Which, as I understand, is what you meant by running indefinitely.

• That goes in an infinite loop, but using this notation for for can save 2 more bytes map($s-=(-1)**$_/(2*$_-1),1..<>),$s=!print$s.$/for 1..<> Commented Feb 5, 2013 at 8:58
• It will only cause an 'infinite' loop if the input given contains an infinite amount of lines. The for<> construction will iterate over every line in input passed to STDIN exactly once, without needing to 'know' beforehand how many there are. Commented Feb 5, 2013 at 9:07