6.13.2 `dabs', `dexp', `dlog', `dsqrt'
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dabs(NUM)
     :: Get the absolute value of NUM.

dexp(NUM)
     :: Get the value of expornent of NUM.

dlog(NUM)
     :: Get the value of logarithm of NUM.

dsqrt(NUM)
     :: Get the value of square root of NUM.

RETURN
     floating point number

NUM
     number

   * Compute numerical values of elementary functions.

   * These functions use the standard mathematical library of C
     language.  So results depend on operating systems and a C
     compilers.

     [0] dexp(1);
     2.71828

