Return to Answer

C# 119 characters:

bool l(string n){return(String.Join("",n.Reverse().Select((x,i)=>(x-48)*(i%2<1?1:2)+"").ToArray()).Sum(x=>x-48))%10<1;}

Not too bad for a code golf n00b in a statically typed language, I hope.

C# 119 characters:

bool l(string n){return(String.Join("",n.Reverse().Select((x,i)=>(x-48)*(i%2<1?1:2)+"").ToArray()).Sum(x=>x-48))%10<1;}

Not too bad for a code golf n00b in a statically typed language, I hope.

This can be reduced to 100:

bool l(string n){return String.Join("",n.Reverse().Select((x,i)=>(x-48)*(i%2+1))).Sum(x=>x+2)%10<1;}

C# 119 characters:

bool l(string n){return(String.Join("",n.Reverse().Select((x,i)=>(x-48)*(i%2<1?2:1)+"").ToArray()).Sum(x=>x-48))%10<1;}

Not too bad for a code golf n00b in a statically typed language, I hope.

C# 119 characters:

bool l(string n){return(String.Join("",n.Reverse().Select((x,i)=>(x-48)*(i%2<1?1:2)+"").ToArray()).Sum(x=>x-48))%10<1;}

Not too bad for a code golf n00b in a statically typed language, I hope.

C# 131 characters:

bool l(string n){var p=n.Reverse();return(String.Join("",p.Select((x,i)=>i%2<1?(x-48)*2+"":x-48+"").ToArray()).Sum(x=>x-48))%10<1;}

Not too bad for a code golf n00b in a statically typed language, I hope.

C# 119 characters:

bool l(string n){return(String.Join("",n.Reverse().Select((x,i)=>(x-48)*(i%2<1?2:1)+"").ToArray()).Sum(x=>x-48))%10<1;}

Not too bad for a code golf n00b in a statically typed language, I hope.