Precedence rules
Precedence rules in C3 differs from C/C++. Here are all precedence levels in C3, listed from highest (1) to lowest (11):
(),[],.,!!postfix!,++and--@, prefix-,~, prefix*,&, prefix++and--- infix
*,/,% <<,>>^,|, infix&+, infix-==,!=,>=,<=,>,<&&||- ternary
?:?? =,*=,/=,%=,+=,-=,<<=,>>=,&=,^=,|=
The main difference is that bitwise operations and shift has higher precedence than addition/subtraction and multiplication/division in C3. Bitwise operations also have higher precedence than the relational operators. Also, there is no difference in precedence between && || or between the bitwise operators.
Examples
a + b >> c + d
(a + b) >> (c + d) // C (+ - are evaluated before >>)
a + (b >> c) + d // C3 (>> is evaluated before + -)
a & b == c
a & (b == c) // C (bitwise operators are evaluated after relational)
(a & b) == c // C3 (bitwise operators are evaluated before relational)
a > b == c < d
(a > b) == (c < d) // C (< > binds tighter than ==)
((a > b) == c) < d // C3 Error, requires parenthesis!
a | b ^ c & d
a | ((b ^ c) & d) // C (All bitwise operators have different precedence)
((a | b) ^ c) & d // C3 Error, requires parenthesis!
The change in precedence of the bitwise operators corrects a long standing issue in the C specification. The change in precedence for shift operations goes towards making the precedence less surprising.
Conflating the precedence of relational and equality operations, and all bitwise operations was motivated by simplification: few remember the exact internal differences in precedence between bitwise operators. Parenthesis are required for those conflated levels of precedence.
Left-to-right offers a very simple model to think about the internal order of operations, and encourages use of explicit ordering, as best practice in C is to use parentheses anyway.