### 16.6 How To Check If MPFR Is Available

Occasionally, you might like to be able to check if `gawk`

was invoked with the `-M` option, enabling arbitrary-precision
arithmetic. You can do so with the following function, contributed
by Andrew Schorr:

# adequate_math_precision --- return true if we have enough bits
function adequate_math_precision(n)
{
return (1 != (1+(1/(2^(n-1)))))
}

Here is code that invokes the function in order to check
if arbitrary-precision arithmetic is available:

BEGIN {
# How many bits of mantissa precision are required
# for this program to function properly?
fpbits = 123
# We hope that we were invoked with MPFR enabled. If so, the
# following statement should configure calculations to our desired
# precision.
PREC = fpbits
if (! adequate_math_precision(fpbits)) {
print("Error: insufficient computation precision available.\n" \
"Try again with the -M argument?") > "/dev/stderr"
# Note: you may need to set a flag here to bail out of END rules
exit 1
}
}

Please be aware that `exit`

will jump to the `END`

rules, if present (see The `exit`

Statement).