Why is size_t unsigned?

[JS]

Doing simple stuff like

for(int i = 0; i < s.length - 1; i++) fails catastrophically if s 
is empty. To make right one has to reduce performance by writing 
extra checks.

There seems to be no real good reason why size_t is unsigned... 
Surely one doesn't require too many strings larger than 2^63 bits 
on an x64 os...

I running into a lot of trouble because of the way D deals with 
implicit casting of between signed and unsigned.

please don't tell me to use foreach... isn't not a panacea.