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Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions compute e (the base of natural logarithms) raised
to the power x.
If the magnitude of the result is too large to be representable,
exp signals overflow.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions compute 2 raised to the power x.
Mathematically, exp2 (x) is the same as exp (x * log (2)).
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions compute 10 raised to the power x.
Mathematically, exp10 (x) is the same as exp (x * log (10)).
These functions are GNU extensions. The name exp10 is
preferred, since it is analogous to exp and exp2.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions compute the natural logarithm of x. exp (log
(x)) equals x, exactly in mathematics and approximately in
C.
If x is negative, log signals a domain error. If x
is zero, it returns negative infinity; if x is too close to zero,
it may signal overflow.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the base-10 logarithm of x.
log10 (x) equals log (x) / log (10).
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the base-2 logarithm of x.
log2 (x) equals log (x) / log (2).
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions extract the exponent of x and return it as a
floating-point value. If FLT_RADIX is two, logb is equal
to floor (log2 (x)), except it’s probably faster.
If x is de-normalized, logb returns the exponent x
would have if it were normalized. If x is infinity (positive or
negative), logb returns ∞. If x is zero,
logb returns ∞. It does not signal.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions are equivalent to the corresponding logb
functions except that they return signed integer values.
Since integers cannot represent infinity and NaN, ilogb instead
returns an integer that can’t be the exponent of a normal floating-point
number. math.h defines constants so you can check for this.
ilogb returns this value if its argument is 0. The
numeric value is either INT_MIN or -INT_MAX.
This macro is defined in ISO C99.
ilogb returns this value if its argument is NaN. The
numeric value is either INT_MIN or INT_MAX.
This macro is defined in ISO C99.
These values are system specific. They might even be the same. The
proper way to test the result of ilogb is as follows:
i = ilogb (f);
if (i == FP_ILOGB0 || i == FP_ILOGBNAN)
{
if (isnan (f))
{
/* Handle NaN. */
}
else if (f == 0.0)
{
/* Handle 0.0. */
}
else
{
/* Some other value with large exponent,
perhaps +Inf. */
}
}
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These are general exponentiation functions, returning base raised to power.
Mathematically, pow would return a complex number when base
is negative and power is not an integral value. pow can’t
do that, so instead it signals a domain error. pow may also
underflow or overflow the destination type.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the nonnegative square root of x.
If x is negative, sqrt signals a domain error.
Mathematically, it should return a complex number.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the cube root of x. They cannot fail; every representable real value has a representable real cube root.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return sqrt (x*x +
y*y). This is the length of the hypotenuse of a right
triangle with sides of length x and y, or the distance
of the point (x, y) from the origin. Using this function
instead of the direct formula is wise, since the error is
much smaller. See also the function cabs in Absolute Value.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return a value equivalent to exp (x) - 1.
They are computed in a way that is accurate even if x is
near zero—a case where exp (x) - 1 would be inaccurate owing
to subtraction of two numbers that are nearly equal.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions returns a value equivalent to log (1 + x).
They are computed in a way that is accurate even if x is
near zero.
ISO C99 defines complex variants of some of the exponentiation and logarithm functions.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return e (the base of natural
logarithms) raised to the power of z.
Mathematically, this corresponds to the value
exp (z) = exp (creal (z)) * (cos (cimag (z)) + I * sin (cimag (z)))
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the natural logarithm of z. Mathematically, this corresponds to the value
log (z) = log (cabs (z)) + I * carg (z)
clog has a pole at 0, and will signal overflow if z equals
or is very close to 0. It is well-defined for all other values of
z.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the base 10 logarithm of the complex value z. Mathematically, this corresponds to the value
log (z) = log10 (cabs (z)) + I * carg (z)
These functions are GNU extensions.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return the complex square root of the argument z. Unlike the real-valued functions, they are defined for all values of z.
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
These functions return base raised to the power of
power. This is equivalent to cexp (y * clog (x))
Next: Hyperbolic Functions, Previous: Inverse Trigonometric Functions, Up: Mathematics [Contents][Index]