This site is a static rendering of the Trac instance that was used by R7RS-WG1 for its work on R7RS-small (PDF), which was ratified in 2013. For more information, see Home. For a version of this page that may be more recent, see FlonumsCowan in WG2's repo for R7RS-large.

Flonums­Cowan

cowan
2012-11-23 15:49:43
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Flonums package

Flonums are a subset of the inexact real numbers provided by a Scheme implementation. In most Schemes, the flonums and the inexact reals are the same.

The procedures in this package don't have hard-coded prefixes. The intent is that they be placed in a module. Users can then import this module with their own prefix such as fl, or ƒ if their Scheme implementation supports that character, or with no prefix at all if the intent is to override the normal Scheme arithmetic routines.

Basic procedures

(flonum? obj)

Returns #t if obj is a flonum, #f otherwise.

(real->flonum x)

Returns the best flonum representation of x.

R7RS-small-compatible procedures

The following R7RS-small procedures have flonum equivalents:

= < <= > >= integer? zero? positive? negative? odd? even? finite? infinite? nan? + - * / abs numerator denominator floor ceiling truncate round log sin cos tan asin acos atan sqrt expt

TODO: need to see about integer division procedures

C99 <math.h> constants

The following constants are defined in terms of the constants of the <math.h> header of ISO/IEC 9899:1999 (C language).

Scheme name

C name

Comments

e

M_E

Value of e

log2-e

M_LOG2E

Value of log2 e

log10-e

M_LOG10E

Value of log10 e

ln-2

M_LN2

Value of loge 2

ln-10

M_LN10

Value of loge 10

pi

M_PI

Value of pi

pi/2

M_PI_2

Value of pi/2

pi/4

M_PI_4

Value of pi/4

one-over-pi

M_1_PI

Value of 1/pi

two-over-pi

M_2_PI

Value of 2/pi

two-over-sqrt-pi

M_2_SQRTPI

Value of 2/sqrt(pi)

sqrt-2

M_SQRT2

Value of sqrt(2)

one-over-sqrt-2

M_SQRT1_2

Value of 1/sqrt(2)

maximum-flonum

HUGE_VAL

+inf.0 or else\\the largest finite flonum

fast-multiply-add

#t if FP_FAST_FMA is 1,\\or #f otherwise

multiply-add is fast

integer-exponent-zero

FP_ILOGB0

what (integer-binary-log 0) returns

integer-exponent-nan

FP_ILOGBNAN

what (integer-binary-log +0.nan) returns

C99 <math.h> procedures

The following procedures are defined in terms of the functions of the <math.h> header of ISO/IEC 9899:1999 (C language). In the C signatures, the types "double" and "int" are mapped to Scheme flonums and (suitably bounded) Scheme exact integers respectively.

Scheme name

C signature

Comments

acosh

double acosh(double)

hyperbolic arc cosine

asinh

double asinh(double)

hyperbolic arc sine

atanh

double atanh(double)

hyperbolic arc tangent

cbrt

double cbrt(double);

cube root

complementary-error-function

double erfc(double)

-

copy-sign

double copysign(double x, double y)

result has magnitude of x and sign of y

cosh

double cosh(double)

hyperbolic cosine

make-flonum

double ldexp(double x, int n)

x*2n

error-function

double erf(double)

-

exp

double exp(double)

ex

exp-binary

double exp,,2,,(double)

base-2 exponential

exp-minus-1

double expm1(double)

ex-1

exponent

double logb(double x)

the exponent of x, which is the integral part of log_r(|x|), as a signed floating-point value, for non-zero x, where r is the radix of the machine's floating-point arithmetic

first-bessel-order-0

double j0(double)

bessel function of the first kind, order 0

first-bessel-order-1

double j1(double)

bessel function of the first kind, order 1

first-bessel

double jn(int n, double)

bessel function of the first kind, order n

fraction-exponent

double modf(double, double *)

returns two values, fraction and int exponent

gamma

double tgamma(double)

-

hypotenuse

double hypot(double, double)

sqrt(x2+y2)

integer-exponent

int ilogb(double)

binary log as int

log-binary

double log2(double)

log base 2

log-decimal

double log10(double)

log base 10

log-gamma

double lgamma(double)

returns two values, log(|gamma(x)|) and sgn(gamma(x))

log-one-plus

double log1p(double x)

log (1+x)

multiply-add

double fma(double a, double b, double c)

a*b+c

next-after

double nextafter(double, double)

next flonum following x in the direction of y

normalized-fraction-exponent

double frexp(double, int *)

returns two values, fraction in range [1/2,1) and int exponent

positive-difference

double fdim(double, double)

-

||remquo||double remquo(double, double, int *)||returns two values, rounded remainder and low-order n bits of the quotient (n is implementation-defined)

scalbn

double scalbn(double x, int y)

x*ry, where r is the machine float radix

second-bessel-order-0

double y0(double)

bessel function of the second kind, order 0

second-bessel-order-1

double y1(double)

bessel function of the second kind, order 1

second-bessel

double yn(int n, double)

bessel function of the second kind, order n

sinh

double cosh(double)

hyperbolic sine

tanh

double cosh(double)

hyperbolic tangent

General remarks

In the event that these operations do not yield a real result for the given arguments, the result may be +nan.0, or may be some unspecified flonum.

Implementations that use IEEE binary floating-point arithmetic should follow the relevant standards for these procedures.

Compnum procedures from <complex.h>

A compnum is a general complex number whose real-part and imag-part are both flonums. The following procedures should be in a different module from the flonum procedures, since they will only be relevant to Schemes that support general complex numbers, and since there are conflicting names.

Scheme name

C signature

Comments

abs

double cabs(double complex)

same as magnitude

acos

double complex cacos(double complex)

-

acosh

double complex cacosh(double complex)

-

angle

double carg(double complex)

-

asin

double complex casin(double complex)

-

asinh

double complex casinh(double complex)

-

atan

double complex catan(double complex)

-

atanh

double complex catanh(double complex)

-

conjugate

double complex conj(double complex)

complex conjugate

cos

double complex ccos(double complex)

-

cosh

double complex ccosh(double complex)

-

exp

double complex cexp(double complex)

-

expt

double complex cpow(double complex, double complex)

-

imag-part

double cimag(double complex)

-

log

double complex clog(double complex)

-

magnitude

double cabs(double complex)

same as abs

||projection||double complex cproj(double complex)||projects to Riemann sphere

real-part

double creal(double complex)

-

sin

double complex csin(double complex)

-

sinh

double complex csinh(double complex)

-

sqrt

double complex csqrt(double complex)

-

tan

double complex ctan(double complex)

-

tanh

double complex ctanh(double complex)

-