3.8 Single-argument math functions

All of the functions described in this section are element-wise. For example, this code–

Array<float,2> A, B;   //
A = sin(B);

results in A(i,j) = sin(B(i,j)) for all (i,j).

ANSI C++ math functions

These math functions are available on all platforms:

abs()

Absolute value

acos()

Inverse cosine. For real arguments, the return value is in the range [0, \pi].

arg()

Argument of a complex number (atan2(Im,Re)).

asin()

Inverse sine. For real arguments, the return value is in the range [-\pi/2, \pi/2].

atan()

Inverse tangent. For real arguments, the return value is in the range [-\pi/2, \pi/2]. See also atan2() in section Math functions 2.

ceil()

Ceiling function: smallest floating-point integer value not less than the argument.

cexp()

Complex exponential; same as exp().

conj()

Conjugate of a complex number.

cos()

Cosine. Works for complex<T>.

cosh()

Hyperbolic cosine. Works for complex<T>.

csqrt()

Complex square root; same as sqrt().

exp()

Exponential. Works for complex<T>.

fabs()

Same as abs().

floor()

Floor function: largest floating-point integer value not greater than the argument.

log()

Natural logarithm. Works for complex<T>.

log10()

Base 10 logarithm. Works for complex<T>.

pow2(), pow3(), pow4(), pow5(), pow6(), pow7(), pow8()

These functions compute an integer power. They expand to a series of multiplications, so they can be used on any type for which multiplication is well-defined.

sin()

Sine. Works for complex<T>.

sinh()

Hyperbolic sine. Works for complex<T>.

sqr()

Same as pow2(). Computes x*x. Works for complex<T>.

sqrt()

Square root. Works for complex<T>.

tan()

Tangent. Works for complex<T>.

tanh()

Hyperbolic tangent. Works for complex<T>.

IEEE/System V math functions

These functions are only available on platforms which provide the IEEE Math library (libm.a) and/or System V Math Library (libmsaa.a). Apparently not all platforms provide all of these functions, so what you can use on your platform may be a subset of these. If you choose to use one of these functions, be aware that you may be limiting the portability of your code.

On some platforms, the preprocessor symbols _XOPEN_SOURCE and/or _XOPEN_SOURCE_EXTENDED need to be defined to use these functions. These symbols can be enabled by compiling with -DBZ_ENABLE_XOPEN_SOURCE. (In previous version of Blitz++, _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED were declared by default. This was found to cause too many problems, so users must manually enable them with -DBZ_ENABLE_XOPEN_SOURCE.).

In the current version, Blitz++ divides these functions into two groups: IEEE and System V. This distinction is probably artificial. If one of the functions in a group is missing, Blitz++ won’t allow you to use any of them. You can see the division of these functions in the files Blitz++/compiler/ieeemath.cpp and Blitz++/compiler/sysvmath.cpp. This arrangement is unsatisfactory and will probably change in a future version.

You may have to link with -lm and/or -lmsaa to use these functions.

None of these functions are available for complex<T>.

acosh()

Inverse hyperbolic cosine

asinh()

Inverse hyperbolic sine

atanh()

Inverse hyperbolic tangent

_class()

Classification of floating point values. The return type is integer and will be one of:

FP_PLUS_NORM

Positive normalized, nonzero

FP_MINUS_NORM

Negative normalized, nonzero

FP_PLUS_DENORM

Positive denormalized, nonzero

FP_MINUS_DENORM

Negative denormalized, nonzero

FP_PLUS_ZERO

+0.0

FP_MINUS_ZERO

-0.0

FP_PLUS_INF

Positive infinity

FP_MINUS_INF

Negative infinity

FP_NANS

Signalling Not a Number (NaNS)

FP_NANQ

Quiet Not a Number (NaNQ)

cbrt()

Cubic root

expm1()

Computes exp(x)-1

erf()

Computes the error function: erf(x) = 2/sqrt(Pi) * integral(exp(-t^2), t=0..x)

Note that for large values of the parameter, calculating can result in extreme loss of accuracy. Instead, use erfc().

erfc()

Computes the complementary error function erfc(x) = 1 - erf(x).

finite()

Returns a nonzero integer if the parameter is a finite number (i.e. not +INF, -INF, NaNQ or NaNS).

ilogb()

Returns an integer which is equal to the unbiased exponent of the parameter.

blitz_isnan()

Returns a nonzero integer if the parameter is NaNQ or NaNS (quiet or signalling Not a Number).

itrunc()

Round a floating-point number to a signed integer. Returns the nearest signed integer to the parameter in the direction of 0.

j0()

Bessel function of the first kind, order 0.

j1()

Bessel function of the first kind, order 1.

lgamma()

Natural logarithm of the gamma function. The gamma function is defined as: Gamma(x) = integral(e^(-t) * t^(x-1), t=0..infinity))

logb()

Returns a floating-point double that is equal to the unbiased exponent of the parameter.

log1p()

Calculates log(1+x), where x is the parameter.

nearest()

Returns the nearest floating-point integer value to the parameter. If the parameter is exactly halfway between two integer values, an even value is returned.

rint()

Rounds the parameter and returns a floating-point integer value. Whether rint() rounds up or down or to the nearest integer depends on the current floating-point rounding mode. If you haven’t altered the rounding mode, rint() should be equivalent to nearest(). If rounding mode is set to round towards +INF, rint() is equivalent to ceil(). If the mode is round toward -INF, rint() is equivalent to floor(). If the mode is round toward zero, rint() is equivalent to trunc().

rsqrt()

Reciprocal square root.

uitrunc()

Returns the nearest unsigned integer to the parameter in the direction of zero.

y0()

Bessel function of the second kind, order 0.

y1()

Bessel function of the second kind, order 1.

There may be better descriptions of these functions in your system man pages.