[lex.fcon] (original) (raw)
5 Lexical conventions [lex]
5.13 Literals [lex.literal]
5.13.4 Floating-point literals [lex.fcon]
floating-point-suffix: one of
f l f16 f32 f64 f128 bf16 F L F16 F32 F64 F128 BF16
[Note 1:
The floating-point suffixesf16, f32, f64, f128, bf16,F16, F32, F64, F128, and BF16are conditionally-supported.
— _end note_]
Table 11 — Types of floating-point-literals [tab:lex.fcon.type]
| 🔗floating-point-suffix | type |
|---|---|
| 🔗none | double |
| 🔗f or F | float |
| 🔗l or L | long double |
| 🔗f16 or F16 | std::float16_t |
| 🔗f32 or F32 | std::float32_t |
| 🔗f64 or F64 | std::float64_t |
| 🔗f128 or F128 | std::float128_t |
| 🔗bf16 or BF16 | std::bfloat16_t |
In the significand, the sequence of digits or hexadecimal-digit_s_and optional period are interpreted as a base N real number s, where N is 10 for a decimal-floating-point-literal and 16 for a hexadecimal-floating-point-literal.
[Note 2:
Any optional separating single quotes are ignored when determining the value.
— _end note_]
If an exponent-part or binary-exponent-partis present, the exponent e of the floating-point-literalis the result of interpreting the sequence of an optional sign and the digit_s_as a base 10 integer.
Otherwise, the exponent e is 0.
The scaled value of the literal is for a decimal-floating-point-literal and for a hexadecimal-floating-point-literal.
[Example 1:
The floating-point-literals 49.625 and 0xC.68p+2 have the same value.
The floating-point-literals 1.602'176'565e-19 and 1.602176565e-19have the same value.
— _end example_]
If the scaled value is not in the range of representable values for its type, the program is ill-formed.
Otherwise, the value of a floating-point-literalis the scaled value if representable, else the larger or smaller representable value nearest the scaled value, chosen in an implementation-defined manner.