Detect division by zero
You are encouraged to solve this task according to the task description, using any language you may know.
Write a function to detect a divide by zero error without checking if the denominator is zero.
D
The following checks a floating number's normality by Floating Point Comparisons in D.
For integral type, either traps exception or pre-checks zero denominator.
module divzero ;
import std.stdio ;
import std.format ;
// check if unordered (NaN)
bool isNaN(T)(T a) { return a !<>= T.min ; }
// check for +ve & -ve infinity
bool isInf(T)(T a) { return a == T.infinity || -a == T.infinity ; }
// check if neither NaN nor Inf
bool isNormal(T)(T a) { return !(a !<> T.infinity || -a !<> T.infinity) ; }
string divCheck(T)(T numer, T denom) {
T result ;
string msg = "" ;
static if (is(T : long)) { // Integral Type
try {
result = numer / denom ;
} catch(Exception e) {
msg = "! " ~ e.msg ~"(by Exception)" ;
result = T.max ;
}
} else { // Float Type
result = numer / denom ;
if(isNormal(numer) && isInf(result))
msg = "! Division by Zero" ;
else if (!isNormal(result)) {
if (isNaN(numer))
msg = "! NaN numerator" ;
else if(isNaN(denom))
msg = "! NaN denominator" ;
else if(isInf(numer))
msg = "! Inf numerator" ;
else
msg = "! <should never displayed this>" ;
}
}
return std.format.format("%5s %s", std.format.format("%1.1g", cast(real)result), msg) ;
}
void main() {
writefln("Div with Check") ;
writefln("int 1/ 0 : %s", divCheck(1, 0)) ;
writefln("ubyte 1/ 0 : %s", divCheck(cast(ubyte)1, cast(ubyte)0)) ;
writefln("real 1/ 0 : %s", divCheck(1.0L, 0.0L)) ;
writefln("real -1/ 0 : %s", divCheck(-1.0L, 0.0L)) ;
writefln() ;
writefln("real -4/-2 : %s", divCheck(-4.0L,-2.0L)) ;
real inf = -1.0L / 0.0L ; // make an infinity float
writefln("real 2/-inf: %s", divCheck(2.0L, inf)) ;
writefln() ;
writefln("real -inf/-2 : %s", divCheck(inf, -2.0L)) ;
writefln("real +inf/-2 : %s", divCheck(real.infinity, -2.0L)) ;
writefln("real nan/-2 : %s", divCheck(real.nan, -2.0L)) ;
writefln("real -2/ nan: %s", divCheck(-2.0L, real.nan)) ;
writefln("real inf/ inf: %s", divCheck(real.infinity, real.infinity)) ;
writefln("real nan/ nan: %s", divCheck(real.nan, real.nan)) ;
}
Output:
Div with Check int 1/ 0 : 2e+09 ! Integer Divide by Zero(by Exception) ubyte 1/ 0 : 3e+02 ! Integer Divide by Zero(by Exception) real 1/ 0 : inf ! Division by Zero real -1/ 0 : -inf ! Division by Zero real -4/-2 : 2 real 2/-inf: -0 real -inf/-2 : inf ! Inf numerator real +inf/-2 : -inf ! Inf numerator real nan/-2 : nan ! NaN numerator real -2/ nan: nan ! NaN denominator real inf/ inf: -nan ! Inf numerator real nan/ nan: nan ! NaN numerator
Java
Two ways to accomplish this task are presented here. They each return true if there is a division by zero or if Double.POSITIVE_INFINITY is used as a numerator.
One way to do this check in Java is to use the isInfinite function from the Double class:
public static boolean infinity(double numer, double denom){
return Double.isInfinite(numer/denom);
}
Another way is to use the ArithmeticException as a check (which is not preferred because it expects an exception):
public static boolean except(double numer, double denom){
try{
int dummy = (int)numer / (int)denom;//ArithmeticException is only thrown from integer math
return false;
}catch(ArithmeticException e){return true;}
}