37_pdfsam_lecture2 - Operators Assignment: = Relational:...

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Unformatted text preview: Operators Assignment: = Relational: >, >=, <, <=, ==, != Logical: &&, ||, ! Binary arithmetic: +, -, *, /, % % is the modulus operator: a%b is the remainder when a is divided by b e.g. 8 % 3 == 2 Shortcut assignment operators +=, -=, *=, /=, %=, etc. e.g. x += 2 // same as x = x + 2 *= 2 // same as x = x * 2 x %= 5+3 // same as x = x % (5+3) Increment/decrement operators There are two types of increment/decrement operators ++x, x : pre-increment, pre-decrement add or subtract 1 from x, and return the new value x++, x : post-increment, post-decrement add or subtract 1 from x, and return the original value Example int a = 10, b, c, d; b = ++a; // a and b are now both 11 c = a++; // a is now 12, c is 11 Three ways to increment. . . Three ways to increment/decrement a variable in C x = x + 1; x += 1; x++; Which you use is a matter of style and eciency x++ may be slightly more ecient than x += 1 x += 1 may be slightly more ecient than x = x + 1 Order of evaluation Operator precedence and associativity rules dene the order in which operators are evaluated Some examples: 5 + 3 / 2 ≡ 5 + (3/2) 1 - 1 - 1 ≡ (1 - 1) - 1 3 < 5 + 2 ≡ 3 < (5 + 2) Class Select Unary Binary Arithmetical Binary Arithmetical Shift Comparison Comparison Binary Bitwise Binary Bitwise Binary Bitwise Binary Boolean Binary Boolean Ternary Assignments Sequence Associativity L→R R→L L→R L→R L→R L→R L→R L→R L→R L→R L→R L→R R→L R→L L→R Operators (...) [...] -> . ! ~ + - * (type) sizeof ++  */% +<< >> < <= > >= == != & ^ | && || ?...: = += -+ *= /= &= |= ^= < <= > >= , Avoid confusing expressions Use parentheses to make precedence clear Q: What does this code do? void main() { ssint a = -2, b = -1, c = 0; ssif( a < b < c ) ssssprintf( True.\n ); sselse ssssprintf( False.\n ); False.True. ssif (a >= b >= c) ssssprintf( True.\n); sselse ssssprintf( False.\n); } ...
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37_pdfsam_lecture2 - Operators Assignment: = Relational:...

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