C Language and Libraries Help (clang.hlp) (Table of Contents; Topic list)
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pow, _powl
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─────Run-Time Library───────────────────────────────────────────────────────
 
     The pow and _powl functions compute <x> raised to the power of
     <y>.
 
     The _powl function uses an 80-bit long double form of arguments
     and return values. In all other respects, it is identical to pow.
 
     Return Value
 
     The pow and _powl functions return the value of <x> raised to the
     power of <y>. The result varies, depending on <x> and <y>:
 
        ■ If <x> is not 0.0 and <y> is 0.0, the functions return 1.0.
 
        ■ If <x> is 0.0 and <y> is negative, the functions set errno to
          EDOM and return 0.0.
 
        ■ If both <x> and <y> are 0.0, or if <x> is negative and <y> is
          not an integer, the functions print a _DOMAIN error message
          to stderr, set errno to EDOM, and return 0.0.
 
        ■ If an overflow results, the functions set errno to ERANGE
          and return ±HUGE_VAL (for pow) or ±_LHUGE_VAL (for _powl). If
          an underflow results, errno is not set and 0.0 is returned.
          No message is printed on overflow or underflow.
 
     The pow function does not recognize integral floating-point values
     greater than 2 to the power of 64, such as 1.0E100.
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