A narrowing conversion changes a value to a type that cannot preserve its full range or precision. The result may be harmless when the value fits, but it may lose information or produce a surprising value when it does not. section 5.4
double a = 1; // Harmless; value fits type
signed short b = -1; // Harmless; value fits type
signed int c = 0x80000000; // Dangerous; value too big for type
signed int d = -0x80000000; // Dangerous; value too big for type
signed int e = -2147483648; // Harmless; value fits type
unsigned short g = 0x80000000; // Loses information; has value 0
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Compare assignments that preserve values with assignments that exceed the destination type. The unsigned-short example loses information and produces zero under the stated modulus assumption. section 5.4
TAKEAWAY
- Avoid narrowing conversions when the destination type may not represent the source value. section 5.4
- Do not use narrow types in arithmetic; mixed operands can also lose range or precision. section 5.4
