[issue11967] Left shift and Right shift for floats
Martin v. Löwis mar...@v.loewis.de added the comment: Ok, I'm closing this as won't fix. Mark is our authority on these matters, and having two spellings for this fairly uncommon operation seems enough. -- resolution: - wont fix status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Raymond Hettinger raymond.hettin...@gmail.com added the comment: A hint that the idea would be useful is that there is an FPU instruction, FSCALE, devoted to this. However, a hint that this isn't needed is that Fortran and MATLAB don't have it. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Changes by Jesús Cea Avión j...@jcea.es: -- nosy: +jcea ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Changes by Daniel Urban urban.dani...@gmail.com: -- nosy: +durban ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Changes by Eric V. Smith e...@trueblade.com: -- nosy: +eric.smith ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Martin v. Löwis mar...@v.loewis.de added the comment: The only way ... That's not true. y=x*(1n) is also an exact multiplication with a power of two, and it's also fairly fast. Likewise for y=x/(1n). -- nosy: +loewis ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Mark Dickinson dicki...@gmail.com added the comment: Would you want x 2 to be equivalent to x / 4.0 or x // 4.0? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Mark Dickinson dicki...@gmail.com added the comment: The only way to do that now is t=frexp(x) and y=ldexp(t[0],t[1]+2). What's wrong with the more direct ldexp(x, 2)? N.B. There *are* edge cases where Martin's suggested alternative won't work. E.g., to compute 1e-300 * 2**1500: ldexp(1e-300, 1500) 3.507466211043404e+151 But: 1e-300 * (1 1500) Traceback (most recent call last): File stdin, line 1, in module OverflowError: long int too large to convert to float I'm -1 on the proposal: I recognise the need for these operations, but I think 'ldexp(x, n)' gives an adequate solution. Fitting the functionality to the and operators is awkward, because that's not what those operators do for integers ( produces the *floor* of the quotient, and doesn't currently accept negative arguments on the right, so there's no neat way for integers to divide by a power of 2). See also the rejected issue 1205239. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
New submission from David Albert Torpey dt...@users.sourceforge.net: I would like to left and right shift floats as a fast way to multiply or divide by a power of 2 without rounding error. The only way to do that now is t=frexp(x) and y=ldexp(t[0],t[1]+2). But would be better to type y=x2. Thank you. -- messages: 134897 nosy: dtorp priority: normal severity: normal status: open title: Left shift and Right shift for floats versions: Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Changes by Ezio Melotti ezio.melo...@gmail.com: -- nosy: +mark.dickinson ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue11967] Left shift and Right shift for floats
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- components: +Interpreter Core nosy: +rhettinger type: - feature request ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue11967 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
