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Source for wiki FlonumsCowan version 9

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cowan

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74.68.121.27

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FlonumsCowan

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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 log,,2,, e||
||`log10-e`||`M_LOG10E`||Value of log,,10,, e||
||`ln-2`||`M_LN2`||Value of log,,e,, 2||
||`ln-10`||`M_LN10`||Value of log,,e,, 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*2^n^||
||`error-function`||`double      erf(double)`||-||
||`exp`||`double exp(double)`||e^x^||
||`exp-binary`||`double      exp,,2,,(double)`||base-2 exponential||
||`exp-minus-1`||`double      expm1(double)`||e^x^-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(x^2^+y^2^)||
||`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*r^y^, 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 library 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)`||-||

== Derived procedures ==

TODO: what library do these go in?

`(cis `''z''`)`

Returns e^i''z''^, a complex number whose real part is cos ''z'' and whose imaginary part is sin ''z''.

`(signum `''z''`)`

Returns a complex number whose phase is the same as ''z'' but whose magnitude is 1, unless ''z'' is zero, in which case it returns ''z''.  As a consequence of this definition, negative real numbers return -1, positive real numbers return 1, and zero returns zero.

`(decode-float `''z''`)` and friends

See [http://www.lispworks.com/documentation/lw50/CLHS/Body/f_dec_fl.htm CL DECODE-FLOAT and friends].
 

time

2012-11-29 04:49:57

version

9