# Gawk/Checking-for-MPFR

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### 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 section The `exit`

Statement).