CAS: log of large integers?

[Joe Horn]

Finally got it working, with Gerald's help.

"biglog", a CAS program.

Input: any positive integer (may be very large).
Output: its common log as a real, accurate to 12 significant places, even for tough inputs (see 3rd example below).

Examples:
biglog(2^7777) --> 2341.11027628 (large correct answer)
biglog(999999999884) --> 11.9999999999 (the correctly rounded answer)
biglog(999999999885) --> 12. (the correctly rounded answer)

#cas
biglog(d):=
BEGIN
LOCAL j,k;
IF type(d)<>DOM_INT THEN RETURN "Argument not integer" END;
d:=abs(d);
k:=string(d);
j:=expr(head(k)+"."+tail(k));
return size(k)-1+evalf(log10(j),13);
END;
#end