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circuitpython/tests/float/float_parse_doubleprec.py

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py/parsenum: Improve parsing of floating point numbers. This patch improves parsing of floating point numbers by converting all the digits (integer and fractional) together into a number 1 or greater, and then applying the correct power of 10 at the very end. In particular the multiple "multiply by 0.1" operations to build a fraction are now combined together and applied at the same time as the exponent, at the very end. This helps to retain precision during parsing of floats, and also includes a check that the number doesn't overflow during the parsing. One benefit is that a float will have the same value no matter where the decimal point is located, eg 1.23 == 123e-2.
2017-11-26 20:51:52 -05:00
# test parsing of floats, requiring double-precision
# very large integer part with a very negative exponent should cancel out
run code formatting script
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print(float("9" * 400 + "e-100"))
print(float("9" * 400 + "e-200"))
print(float("9" * 400 + "e-400"))
py/parsenum: Improve parsing of floating point numbers. This patch improves parsing of floating point numbers by converting all the digits (integer and fractional) together into a number 1 or greater, and then applying the correct power of 10 at the very end. In particular the multiple "multiply by 0.1" operations to build a fraction are now combined together and applied at the same time as the exponent, at the very end. This helps to retain precision during parsing of floats, and also includes a check that the number doesn't overflow during the parsing. One benefit is that a float will have the same value no matter where the decimal point is located, eg 1.23 == 123e-2.
2017-11-26 20:51:52 -05:00
# many fractional digits
run code formatting script
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print(float("." + "9" * 400))
print(float("." + "9" * 400 + "e100"))
print(float("." + "9" * 400 + "e-100"))
py/parsenum: Improve parsing of floating point numbers. This patch improves parsing of floating point numbers by converting all the digits (integer and fractional) together into a number 1 or greater, and then applying the correct power of 10 at the very end. In particular the multiple "multiply by 0.1" operations to build a fraction are now combined together and applied at the same time as the exponent, at the very end. This helps to retain precision during parsing of floats, and also includes a check that the number doesn't overflow during the parsing. One benefit is that a float will have the same value no matter where the decimal point is located, eg 1.23 == 123e-2.
2017-11-26 20:51:52 -05:00
# tiny fraction with large exponent
run code formatting script
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print("%.14e" % float("." + "0" * 400 + "9e100"))
print("%.14e" % float("." + "0" * 400 + "9e200"))
print("%.14e" % float("." + "0" * 400 + "9e400"))
py/parsenum: Fix parsing of floats that are close to subnormal. Prior to this patch, a float literal that was close to subnormal would have a loss of precision when parsed. The worst case was something like float('10000000000000000000e-326') which returned 0.0.
2018-02-07 22:02:50 -05:00
# ensure that accuracy is retained when value is close to a subnormal
run code formatting script
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print(float("1.00000000000000000000e-307"))
print(float("10.0000000000000000000e-308"))
print(float("100.000000000000000000e-309"))