Issue 22325: wrong subtraction result (original) (raw)

I was using python as my calculator when I got a result which had to be rounded to be the value I expected. So I made some tests with a simple case. Given that 0.38 - 0.20 = 0.18, then 1000.38 - 1000.20 should be also 0.18.

Here is this calculation done on three different systems:

Python 2.7.5 (default, Mar 9 2014, 22:15:05) [GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)] on darwin Type "help", "copyright", "credits" or "license" for more information.

0.38 - 0.20 0.18 test = lambda x: (x+0.38) - (x+0.20) test(0) 0.18 test(1000) 0.17999999999994998 test(1000000) 0.18000000005122274 test(1000000000) 0.1799999475479126 test(1000000000000) 0.1800537109375 test(1000000000000000) 0.125

Python 2.7.3 (default, Mar 13 2014, 11:03:55) [GCC 4.7.2] on linux2 Type "help", "copyright", "credits" or "license" for more information.

0.38 - 0.20 0.18 test = lambda x: (x+0.38) - (x+0.20) test(0) 0.18 test(1000) 0.17999999999994998 test(1000000000000000) 0.125

Python 2.4.3 (#1, Oct 23 2012, 22:02:41) [GCC 4.1.2 20080704 (Red Hat 4.1.2-54)] on linux2 Type "help", "copyright", "credits" or "license" for more information.

0.38 - 0.20 0.17999999999999999 test = lambda x: (x+0.38) - (x+0.20) test(0) 0.17999999999999999 test(1000) 0.17999999999994998 test(1000000000000000) 0.125