أولوية المعاملات في السي
الجدول التالي يبين قواعد أولوية وربط المعاملات في السي. المعاملات مرتبة تبعا تنازليا طبعا ل اولويتها.
||Suffix/postfix increment and decrement||من اليسار إلى اليمين|
||Structure and union member access|
||Structure and union member access through pointer|
||Prefix increment and decrement||من اليمين إلى اليسار|
||Unary plus and minus|
||Logical NOT and bitwise NOT|
||Multiplication, division, and remainder||من اليسار إلى اليمين|
||Addition and subtraction|
||Bitwise left shift and right shift|
||For relational operators < and ≤ respectively|
||For relational operators > and ≥ respectively|
||For relational = and ≠ respectively|
||Bitwise XOR (exclusive or)|
||Bitwise OR (inclusive or)|
||Ternary conditional[note ٢]||من اليمين إلى اليسار|
||Assignment by sum and difference|
||Assignment by product, quotient, and remainder|
||Assignment by bitwise left shift and right shift|
||Assignment by bitwise AND, XOR, and OR|
||Comma||من اليسار إلى اليمين|
- Fictional precedence level, see Notes below
- The expression in the middle of the conditional operator (between ? and :) is parsed as if parenthesized: its precedence relative to
When parsing an expression, an operator which is listed on some row will be bound tighter (as if by parentheses) to its arguments than any operator that is listed on a row further below it. For example, the expression *p++ is parsed as *(p++), and not as (*p)++.
Operators that are in the same cell (there may be several rows of operators listed in a cell) are evaluated with the same precedence, in the given direction. For example, the expression a=b=c is parsed as a=(b=c), and not as (a=b)=c because of right-to-left associativity.
Precedence and associativity are independent from order of evaluation.
The C language standard doesn't specify operator precedence. It specifies the language grammar, and the precedence table is derived from it to simplify understanding. There is a part of the grammar that cannot be represented by a precedence table: assignment is never allowed to appear on the right hand side of a conditional operator, so e = a < d ? a++ : a = d is an expression that cannot be parsed, and therefore relative precedence of conditional and assignment operators cannot be described easily.
However, many C compilers use non-standard expression grammar where
?: is designated higher precedence than
=, which parses that expression as e = ( ((a < d) ? (a++) : a) = d ), which then fails to compile due to semantic constraints:
?: is never lvalue and
= requires a modifiable lvalue on the left. This is the table presented on this page.
Note that this is different in C++, where the conditional operator has the same precedence as assignment.
[تعديل] أنظر أيضا
Order of evaluation of operator arguments at run time.
a = b
a == b
مقالة مرجع C++ عن C++ operator precedence