Arithmetic operators apply standard mathematical operations to their operands.
Operator  Operator name  Example  Result 

+  unary plus  +a  the value of a after promotions 
  unary minus  a  the negative of a 
+  addition  a + b  the addition of a and b 
  subtraction  a  b  the subtraction of b from a 
*  product  a * b  the product of a and b 
/  division  a / b  the division of a by b 
%  modulo  a % b  the remainder of a divided by b 
~  bitwise NOT  ~a  the bitwise NOT of a 
&  bitwise AND  a & b  the bitwise AND of a and b 
  bitwise OR  a  b  the bitwise OR of a and b 
^  bitwise XOR  a ^ b  the bitwise XOR of a and b 
<<  bitwise left shift  a << b  a left shifted by b 
>>  bitwise right shift  a >> b  a right shifted by b 
Unsigned integer arithmetic is always performed modulo 2n
where n is the number of bits in that particular integer. E.g. for unsigned int
, adding one to UINT_MAX
gives 0
, and subtracting one from 0
gives UINT_MAX
.
When signed integer arithmetic operation overflows (the result does not fit in the result type), the behavior is undefined: it may wrap around according to the rules of the representation (typically 2's complement), it may trap on some platforms or due to compiler options (e.g. ftrapv
in GCC and Clang), or may be completely optimized out by the compiler.
If #pragma STDC FENV_ACCESS
is set to ON
, all floatingpoint arithmetic operators obey the current floatingpoint rounding direction and report floatingpoint arithmetic errors as specified in math_errhandling
unless part of a static initializer (in which case floatingpoint exceptions are not raised and the rounding mode is to nearest).
Unless #pragma STDC FP_CONTRACT
is set to OFF
, all floatingpoint arithmetic may be performed as if the intermediate results have infinite range and precision, that is optimizations that omit rounding errors and floatingpoint exceptions that would be observed if the expression was evaluated exactly as written. For example, allows the implementation of (x*y) + z
with a single fused multiplyadd CPU instruction or optimization of a = x*x*x*x;
as tmp = x*x; a = tmp*tmp
.
Unrelated to contracting, intermediate results of floatingpoint arithmetic may have range and precision that is different from the one indicated by its type, see FLT_EVAL_METHOD
.
The unary arithmetic operator expressions have the form.
+ expression  (1)  
 expression  (2) 
Both unary plus and unary minus first apply integral promotions to their operand, and then.
The type of the expression is the type after promotion, and the value category is nonlvalue.
The unary minus invokes undefined behavior due to signed integer overflow when applied to INT_MIN
, LONG_MIN
, or LLONG_MIN
, on typical (2's complement) platforms.
In C++, unary operator + can also be used with other builtin types such as arrays and functions, not so in C.
#include <stdio.h> #include <complex.h> int main(void) { char c = 'a'; printf("sizeof char: %zu sizeof int: %zu\n", sizeof c, sizeof +c); printf("1, where 1 is signed: %d\n", 1); printf("1, where 1 is unsigned: %u\n", 1u); double complex z = 1 + 2*I; printf("(1+2i) = %.1f%+.1f\n", creal(z), cimag(z)); }
Possible output:
sizeof char: 1 sizeof int: 4 1, where 1 is signed: 1 1, where 1 is unsigned: 4294967295 (1+2i) = 1.02.0
The binary additive arithmetic operator expressions have the form.
lhs + rhs  (1)  
lhs  rhs  (2) 
If both operands have arithmetic types, then.
FE_INVALID
is raised FE_INVALID
is raised Complex and imaginary addition and subtraction are defined as follows (note the result type is imaginary if both operands are imaginary and complex if one operand is real and the other imaginary, as specified by the usual arithmetic conversions):
+ or   u  iv  u + iv 

x  x ± u  x ± iv  (x ± u) ± iv 
iy  ±u + iy  i(y ± v)  ±u + i(y ± v) 
x + iy  (x ± u) + iy  x + i(y ± v)  (x ± u) + i(y ± v) 
// work in progress // note: take part of the c/language/conversion example
P
points at an element of an array with index I
, then P+N
and N+P
are pointers that point at an element of the same array with index I+N
PN
is a pointer that points at an element of the same array with index {ttIN}} The behavior is defined only if both the original pointer and the result pointer are pointing at elements of the same array or one past the end of that array. Note that executing p1 when p points at the first element of an array is undefined behavior and may fail on some platforms.
P1
points at an element of an array with index I
(or one past the end) and P2
points at an element of the same array with index J
(or one past the end), then P1P2
has the value equal to JI
and the type ptrdiff_t
(which is a signed integer type, typically half as large as the size of the largest object that can be declared) The behavior is defined only if the result fits in ptrdiff_t
.
For the purpose of pointer arithmetic, a pointer to an object that is not an element of any array is treated as a pointer to the first element of an array of size 1.
// work in progress int n = 4, m = 3; int a[n][m]; // VLA of 4 VLAs of 3 ints each int (*p)[m] = a; // p == &a[0] p = p + 1; // p == &a[1] (pointer arithmetic works with VLAs just the same) (*p)[2] = 99; // changes a[1][2]
The binary multiplicative arithmetic operator expressions have the form.
lhs * rhs  (1)  
lhs / rhs  (2)  
lhs % rhs  (3) 
The binary operator * performs multiplication of its operands (after usual arithmetic conversions) following the usual arithmetic definitions, except that.
FE_INVALID
is raised Because in C, any complex value with at least one infinite part as an infinity even if its other part is a NaN, the usual arithmetic rules do not apply to complexcomplex multiplication. Other combinations of floating operands follow the following table:
*  u  iv  u + iv 

x  xu  i(xv)  (xu) + i(xv) 
iy  i(yu)  −yv  (−yv) + i(yu) 
x + iy  (xu) + i(yu)  (−yv) + i(xv)  special rules 
Besides infinity handling, complex multiplication is not allowed to overflow intermediate results, except when #pragma STDC CX_LIMITED_RANGE
is set to ON
, in which case the value may be calculated as if by (x+iy)×(u+iv) = (xuyv)+i(yu+xv), as the programmer assumes the responsibility of limiting the range of the operands and dealing with the infinities.
Despite disallowing undue overflow, complex multiplication may raise spurious floatingpoint exceptions (otherwise it is prohibitively difficult to implement nonoverflowing versions).
#include<stdio.h> #include <stdio.h> #include <complex.h> #include <math.h> int main(void) { // TODO simpler cases, take some from C++ double complex z = (1 + 0*I) * (INFINITY + I*INFINITY); // textbook formula would give // (1+i0)(∞+i∞) ⇒ (1×∞ – 0×∞) + i(0×∞+1×∞) ⇒ NaN + I*NaN // but C gives a complex infinity printf("%f + i*%f\n", creal(z), cimag(z)); // textbook formula would give // cexp(∞+iNaN) ⇒ exp(∞)×(cis(NaN)) ⇒ NaN + I*NaN // but C gives ±∞+i*nan double complex y = cexp(INFINITY + I*NAN); printf("%f + i*%f\n", creal(y), cimag(y)); }
Possible output:
inf + i*inf inf + i*nan
The binary operator / divides the first operand by the second (after usual arithmetic conversions) following the usual arithmetics definitions, except that.
result of the / operator is a complex infinity.
result of the / operator is a zero.
Because in C, any complex value with at least one infinite part as an infinity even if its other part is a NaN, the usual arithmetic rules do not apply to complexcomplex division. Other combinations of floating operands follow the following table:
/  u  iv 

x  x/u  i(−x/v) 
iy  i(y/u)  y/v 
x + iy  (x/u) + i(y/u)  (y/v) + i(−x/v) 
Besides infinity handling, complex division is not allowed to overflow intermediate results, except when #pragma STDC CX_LIMITED_RANGE
is set to ON
, in which case the value may be calculated as if by (x+iy)/(u+iv) = [(xu+yv)+i(yuxv)]/(u2
+v2
), as the programmer assumes the responsibility of limiting the range of the operands and dealing with the infinities.
Despite disallowing undue overflow, complex division may raise spurious floatingpoint exceptions (otherwise it is prohibitively difficult to implement nonoverflowing versions).
If the second operand is zero, the behavior is undefined, except that if the IEEE floatingpoint arithmetic is supported, and the floatingpoint division is taking place, then.
FE_DIVBYZERO
is raised FE_INVALID
is raised The binary operator % yields the remainder of the division of the first operand by the second (after usual arithmetic conversions).
The sign of the remainder is defined in such a way that if the quotient a/b
is representable in the result type, then (a/b)*b + a%b == a
.
If the second operand is zero, the behavior is undefined.
If the quotient a/b
is not representable in the result type, the behavior of both a/b
and a%b
is undefined (that means INT_MIN%1
is undefined on 2's complement systems).
Note: the remainder operator does not work on floatingpoint types, the library function fmod
provides that functionality.
The bitwise arithmetic operator expressions have the form.
~ rhs  (1)  
lhs & rhs  (2)  
lhs  rhs  (3)  
lhs ^ rhs  (4) 
where.
lhs, rhs    expressions of integer type 
First, operators &, ^, and  perform usual arithmetic conversions on both operands and the operator ~ performs integer promotions on its only operand.
Then, the corresponding binary logic operators are applied bitwise; that is, each bit of the result is set or cleared according to the logic operation (NOT, AND, OR, or XOR), applied to the corresponding bits of the operands.
Note: bitwise operators are commonly used to manipulate bit sets and bit masks.
Note: for unsigned types (after promotion), the expression ~E is equivalent to the maximum value representable by the result type minus the original value of E.
#include <stdio.h> #include <stdint.h> int main(void) { uint16_t mask = 0x00f0; uint32_t a = 0x12345678; printf("Value: %#x mask: %#x\n" "Setting bits: %#x\n" "Clearing bits: %#x\n" "Selecting bits: %#x\n", a,mask,(amask),(a&~mask),(a&mask)); }
Possible output:
Value: 0x12345678 mask: 0xf0 Setting bits: 0x123456f8 Clearing bits: 0x12345608 Selecting bits: 0x70
The bitwise shift operator expressions have the form.
lhs << rhs  (1)  
lhs >> rhs  (2) 
where.
lhs, rhs    expressions of integer type 
First, integer promotions are performed, individually, on each operand (Note: this is unlike other binary arithmetic operators, which all perform usual arithmetic conversions). The type of the result is the type of lhs after promotion.
For unsigned lhs, the value of LHS << RHS
is the value of LHS * 2RHS
, reduced modulo maximum value of the return type plus 1 (that is, bitwise left shift is performed and the bits that get shifted out of the destination type are discarded). For signed lhs with nonnegative values, the value of LHS << RHS
is LHS * 2RHS
if it is representable in the promoted type of lhs, otherwise the behavior is undefined.
For unsigned lhs and for signed lhs with nonnegative values, the value of LHS >> RHS
is the integer part of LHS / 2RHS
. For negative LHS
, the value of LHS >> RHS
is implementationdefined where in most implementations, this performs arithmetic right shift (so that the result remains negative). Thus in most implementations, right shifting a signed LHS
fills the new higherorder bits with the original sign bit (i.e. with 0 if it was nonnegative and 1 if it was negative).
In any case, the behavior is undefined if rhs is negative or is greater or equal the number of bits in the promoted lhs.
#include <stdio.h> enum {ONE=1, TWO=2}; int main(void) { char c = 0x10; unsigned long long ulong_num = 0x123; printf("0x123 << 1 = %#llx\n" "0x123 << 63 = %#llx\n" // overflow truncates high bits for unsigned numbers "0x10 << 10 = %#x\n", // char is promoted to int ulong_num << 1, ulong_num << 63, c << 10); long long long_num = 1000; printf("1000 >> 1 = %lld\n", long_num >> ONE); // implementation defined }
Possible output:
0x123 << 1 = 0x246 0x123 << 63 = 0x8000000000000000 0x10 << 10 = 0x4000 1000 >> 1 = 500
Common operators  

assignment  increment decrement  arithmetic  logical  comparison  member access  other 







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