Rework the conversion of floats to decimal strings so it aligns precisely
with the conversion of strings to floats in parsenum.c. This is to avoid
rendering 1eX as 9.99999eX-1 etc. This is achieved by removing the power-
of-10 tables and using pow() to compute the exponent directly, and that's
done efficiently by first estimating the power-of-10 exponent from the
power-of-2 exponent in the floating-point representation.
Code size is reduced by roughly 100 to 200 bytes by this commit.
Signed-off-by: Dan Ellis <dan.ellis@gmail.com>
Formerly, py/formatfloat would print whole numbers inaccurately with
nonzero digits beyond the decimal place. This resulted from its strategy
of successive scaling of the argument by 0.1 which cannot be exactly
represented in floating point. The change in this commit avoids scaling
until the value is smaller than 1, so all whole numbers print with zero
fractional part.
Fixes issue #4212.
Signed-off-by: Dan Ellis dan.ellis@gmail.com
Prior to this patch, some architectures (eg unix x86) could render floats
with "negative" digits, like ")". For example, '%.23e' % 1e-80 would come
out as "1.0000000000000000/)/(,*0e-80". This patch fixes the known cases.
Prior to this patch, some architectures (eg unix x86) could render floats
with a ":" character in them, eg 1e+39 would come out as ":e+38" (":" is
just after "9" in ASCII so this is like 10e+38). This patch fixes some of
these cases.
Prior to this patch the %f formatting of some FP values could be off by up
to 1, eg '%.0f' % 123 would return "122" (unix x64). Depending on the FP
precision (single vs double) certain numbers would format correctly, but
others wolud not. This patch should fix all cases of rounding for %f.
This patch fixes 2 things when printing a floating-point number that
requires rounding up of the mantissa:
- retain the correct precision; eg 0.99 becomes 1.0, not 1.00
- if the exponent goes from -1 to 0 then render it as +0, not -0
When taking the logarithm of the float to determine the exponent, there
are some edge cases that finish the log loop too large. Eg for an
input value of 1e32-epsilon, this is actually less than 1e32 from the
log-loop table and finishes as 10.0e31 when it should be 1.0e32. It
is thus rendered as :e32 (: comes after 9 in ascii).
There was the same problem with numbers less than 1.
For single prec, exponents never get larger than about 37. For double
prec, exponents can be larger than 99 and need 3 bytes to format. This
patch makes the number of bytes needed configurable.
Addresses issue #1772.
This takes previous IEEE-754 single precision float implementation, and
converts it to fully portable parametrizable implementation using C99
functions like signbit(), isnan(), isinf(). As long as those functions
are available (they can be defined in adhoc manner of course), and
compiler can perform standard arithmetic and comparison operations on a
float type, this implementation will work with any underlying float type
(including types whose mantissa is larger than available intergral integer
type).
This allows using (almost) the same code for printing floats everywhere,
removes the dependency on sprintf and uses just snprintf and
applies an msvc-specific fix for snprintf in a single place so
nan/inf are now printed correctly.
In particular, numbers which are less than 1.0 but which
round up to 1.0.
This also makes those numbers which round up to 1.0 to
print with e+00 rather than e-00 for those formats which
print exponents.
Addresses issue #1178.
Blanket wide to all .c and .h files. Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.
Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.
This adds support for almost everything (the comma isn't currently
supported).
The "unspecified" type with floats also doesn't behave exactly like
python.
Tested under unix with float and double
Spot tested on stmhal
Damien George