Resolve quadratic equation

Question

Challenge:

Write the smallest program (in characters) that resolves quadratic equations i.e. ax² + bx + c = 0

Rules:

Given 3 numbers in R comma-delimited on STDIN: a,b,c (a != 0), print on STDOUT the 2 roots in C, one per line.

R stands for real numbers, C for complex numbers.

Examples:

Input         Output

1,0,0         r1=0     also accepted: r1=(-0-sqrt(0))/2
              r2=0

1,2,1         r1=-1    also accepted: r1=(-2-sqrt(0))/2
              r2=-1

1,1,1         r1=(-1-isqrt(3))/2  also accepted: r1=(-1-sqrt(-3))/2 or r1=-0.5-0.866i
              r2=(-1+isqrt(3))/2

Answer 1

R, 19 chars

polyroot(scan(n=3))

or more strictly following the I/O requirements in 58 chars:

r=polyroot(rev(scan(sep=",")));cat("r1=",r[1],"\nr2=",r[2])

edit: reversed coefficients

Answer 2

J, 21

J's got a verb to do exactly that: p. It does complex to complex, but your problem is a subset of that.

echo"0>{:p.|.".1!:1[3

As always with J solutions here, I/O and formatting take up 90% of the solution.

Answer 3

Python 3, 79 chars

a,b,c=eval(input())
d=(b*b-4*a*c)**.5/2/a
x=-b/2/a
print('r1=',x+d,'\nr2=',x-d)

Python's imaginary unity is j and not i. I used Python 3 because the power operator works also on negative numbers.

BTW, is it really needed to write r1= ... and r2= ... ?

Answer 4

Perl, 96 87 Characters

($a,$b,$c)=eval<>;$_=abs($_=$b*$b-4*$a*$c)**.5/2/$a.i x($_<0);$b/=-2*$a;die"r1=$b+$_
r2=$b-$_"

The line break is intentional, as is a space.

Edit: By reformatting output, I can shorten this to:

($a,$b,$c)=eval<>;$_="sqrt(".($b*$b-4*$a*$c)."))/".2*$a;$b*=-1;die"r1=($b+$_
r2=($b-$_"

Answer 5

Perl, 76 characters (+1 command line switch)

perl -pe '($a,$b,$c)=eval;$d=($b/=-$a)**2-4*$c/$a;$_="-+";s!.!r@+=($b$&sqrt($d))/2\n!g'

Replacing the \n with a literal newline allows a further trivial one-character reduction.

Sample input / output:

1,0,0
r1=(0-sqrt(0))/2
r2=(0+sqrt(0))/2
1,2,1
r1=(-2-sqrt(0))/2
r2=(-2+sqrt(0))/2
1,1,1
r1=(-1-sqrt(-3))/2
r2=(-1+sqrt(-3))/2
1,0,-1
r1=(0-sqrt(4))/2
r2=(0+sqrt(4))/2
2,1,1
r1=(-0.5-sqrt(-1.75))/2
r2=(-0.5+sqrt(-1.75))/2

Yeah, it's not exactly Wolfram Alpha, but I believe it should qualify as acceptable output.

Answer 6

D (160 chars)

import std.complex;import std.stdio;void main(){real a,b,c;readf("%f,%f,%f",&a,&b,&c);Complex!real j=sqrt(b*b-4*a*c)/2/a,i=-b/2/a;write("r1=",i+j,"\nr2=",i-j);}

Answer 7

Perl, 101 chars

First stab:

perl -E 'my($x,$y,$z)=pop=~/\d+/g;printf"r%d=(%+d%ssqrt(%d))/%d\n",++$p,-$y,$_,$y**2-4*$x*$z,2*$x for qw/- +/;' 1,2,1