The format of floating point numbers recognized by the outer (aka text)
interpreter is: a signed decimal number, possibly containing a decimal
point (.), followed by E or e, optionally followed
by a signed integer (the exponent). E.g., 1e is the same as
+1.0e+0. Note that a number without e is not interpreted
as floating-point number, but as double (if the number contains a
.) or single precision integer. Also, conversions between string
and floating point numbers always use base 10, irrespective of the value
of BASE (in Gforth; for the standard this is an ambiguous
condition). If BASE contains a value greater then 14, the
E may be interpreted as digit and the number will be interpreted
as integer, unless it has a signed exponent (both + and -
are allowed as signs).
Angles in floating point operations are given in radians (a full circle has 2 pi radians). Note, that Gforth has a separate floating point stack, but we use the unified notation.
Floating point numbers have a number of unpleasant surprises for the unwary (e.g., floating point addition is not associative) and even a few for the wary. You should not use them unless you know what you are doing or you don't care that the results you get are totally bogus. If you want to learn about the problems of floating point numbers (and how to avoid them), you might start with David Goldberg, What Every Computer Scientist Should Know About Floating-Point Arithmetic, ACM Computing Surveys 23(1):5-48, March 1991 (http://www.validgh.com/goldberg/paper.ps).
f+ r1 r2 -- r3 float ``f-plus''
f- r1 r2 -- r3 float ``f-minus''
f* r1 r2 -- r3 float ``f-star''
f/ r1 r2 -- r3 float ``f-slash''
fnegate r1 -- r2 float ``fnegate''
fabs r1 -- r2 float-ext ``fabs''
fmax r1 r2 -- r3 float ``fmax''
fmin r1 r2 -- r3 float ``fmin''
floor r1 -- r2 float ``floor''
round towards the next smaller integral value, i.e., round toward negative infinity
fround r1 -- r2 float ``fround''
round to the nearest integral value
f** r1 r2 -- r3 float-ext ``f-star-star''
r3 is r1 raised to the r2th power
fsqrt r1 -- r2 float-ext ``fsqrt''
fexp r1 -- r2 float-ext ``fexp''
fexpm1 r1 -- r2 float-ext ``fexpm1''
r2=e**r1-1
fln r1 -- r2 float-ext ``fln''
flnp1 r1 -- r2 float-ext ``flnp1''
r2=ln(r1+1)
flog r1 -- r2 float-ext ``flog''
the decimal logarithm
falog r1 -- r2 float-ext ``falog''
r2=10**r1
fsin r1 -- r2 float-ext ``fsin''
fcos r1 -- r2 float-ext ``fcos''
fsincos r1 -- r2 r3 float-ext ``fsincos''
r2=sin(r1), r3=cos(r1)
ftan r1 -- r2 float-ext ``ftan''
fasin r1 -- r2 float-ext ``fasin''
facos r1 -- r2 float-ext ``facos''
fatan r1 -- r2 float-ext ``fatan''
fatan2 r1 r2 -- r3 float-ext ``fatan2''
r1/r2=tanr3. The standard does not require, but probably
intends this to be the inverse of fsincos. In gforth it is.
fsinh r1 -- r2 float-ext ``fsinh''
fcosh r1 -- r2 float-ext ``fcosh''
ftanh r1 -- r2 float-ext ``ftanh''
fasinh r1 -- r2 float-ext ``fasinh''
facosh r1 -- r2 float-ext ``facosh''
fatanh r1 -- r2 float-ext ``fatanh''
Go to the first, previous, next, last section, table of contents.