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f9cbe6bc47
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
32 lines
1.4 KiB
Python
32 lines
1.4 KiB
Python
# Test that integers format to exact values.
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for b in [13, 123, 457, 23456]:
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for r in range(1, 10):
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e_fmt = "{:." + str(r) + "e}"
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f_fmt = "{:." + str(r) + "f}"
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g_fmt = "{:." + str(r) + "g}"
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for e in range(0, 5):
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f = b * (10**e)
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title = str(b) + " x 10^" + str(e)
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print(title, "with format", e_fmt, "gives", e_fmt.format(f))
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print(title, "with format", f_fmt, "gives", f_fmt.format(f))
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print(title, "with format", g_fmt, "gives", g_fmt.format(f))
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# Check that powers of 10 (that fit in float32) format correctly.
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for i in range(31):
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# It works to 12 digits on all platforms *except* qemu-arm, where
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# 10^11 comes out as 10000000820 or something.
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print("{:.7g}".format(float("1e" + str(i))))
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# 16777215 is 2^24 - 1, the largest integer that can be completely held
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# in a float32.
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print("{:f}".format(16777215))
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# 4294967040 = 16777215 * 128 is the largest integer that is exactly
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# represented by a float32 and that will also fit within a (signed) int32.
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# The upper bound of our integer-handling code is actually double this,
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# but that constant might cause trouble on systems using 32 bit ints.
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print("{:f}".format(2147483520))
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# Very large positive integers can be a test for precision and resolution.
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# This is a weird way to represent 1e38 (largest power of 10 for float32).
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print("{:.6e}".format(float("9" * 30 + "e8")))
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