Go 语言规范Representability
A constant x is representable by a value of type T if one of the following conditions applies:
xis in the set of values determined byT.Tis a floating-point type andxcan be rounded toT's precision without overflow. Rounding uses IEEE 754 round-to-even rules but with an IEEE negative zero further simplified to an unsigned zero. Note that constant values never result in an IEEE negative zero, NaN, or infinity.Tis a complex type, andx's componentsreal(x)andimag(x)are representable by values ofT's component type (float32orfloat64).
x T x is representable by a value of T because
'a' byte 97 is in the set of byte values
97 rune rune is an alias for int32, and 97 is in the set of 32-bit integers
"foo" string "foo" is in the set of string values
1024 int16 1024 is in the set of 16-bit integers
42.0 byte 42 is in the set of unsigned 8-bit integers
1e10 uint64 10000000000 is in the set of unsigned 64-bit integers
2.718281828459045 float32 2.718281828459045 rounds to 2.7182817 which is in the set of float32 values
-1e-1000 float64 -1e-1000 rounds to IEEE -0.0 which is further simplified to 0.0
0i int 0 is an integer value
(42 + 0i) float32 42.0 (with zero imaginary part) is in the set of float32 valuesx T x is not representable by a value of T because
0 bool 0 is not in the set of boolean values
'a' string 'a' is a rune, it is not in the set of string values
1024 byte 1024 is not in the set of unsigned 8-bit integers
-1 uint16 -1 is not in the set of unsigned 16-bit integers
1.1 int 1.1 is not an integer value
42i float32 (0 + 42i) is not in the set of float32 values
1e1000 float64 1e1000 overflows to IEEE +Inf after rounding
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