On 3/6/2014 6:34 AM, candide wrote:
According to the official documentation, the ternary operator has
left-to-right associativity :
The proper terms is 'conditional expression', which goes back to "The C
Programming Language" (K&R). There are many unary operators, many binary
operators, and there could be other ternary operators.
------------------- Operators in the same box group left to right
(except for comparisons, including tests, which all have the same
precedence and chain from left to right -- see section Comparisons --
and exponentiation, which groups from right to left).
-------------------
Nevertheless, the ternary operator grouping seems to be from right to
left, compare :
p = 0 if 1 else 0 if 0 else 1 p
0
left_to_right = (0 if 1 else 0) if 0 else 1
>>>> right_to_left = 0 if 1 else (0 if 0 else 1)
>>>> p == left_to_right
False
p == right_to_left
True
This behavior is specified in the grammar as given in the C-E section.
The doc is also inconsistent about evaluation order and precedence. I
opened http://bugs.python.org/issue20859 .
--
Terry Jan Reedy
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