#C, 48 chars
i(n,b){n?i(n/b,b),putchar(n%b+48+(n%b>9)*39):0;}
- input of 0 produces empty string
#C, 77 chars, prints 0
for zero
j(n,b){n?j(n/b,b),putchar(n%b+48+(n%b>9)*39):0;}I(n,b){n?j(n,b):putchar(48);}
#C, 48 chars
i(n,b){n?i(n/b,b),putchar(n%b+48+(n%b>9)*39):0;}
#C, 77 chars, prints 0
for zero
j(n,b){n?j(n/b,b),putchar(n%b+48+(n%b>9)*39):0;}I(n,b){n?j(n,b):putchar(48);}