5 Lexical conventions [lex]

In an integer-literal, the sequence of binary-digits, octal-digits, digits, or hexadecimal-digits is interpreted as a base N integer as shown in table Table 7; the lexically first digit of the sequence of digits is the most significant.

[Note 1:

The prefix and any optional separating single quotes are ignored when determining the value.

— end note]

Table 7 — Base of integer-literals [tab:lex.icon.base]

🔗 Kind of integer-literal	base N
🔗 binary-literal	2
🔗 octal-literal	8
🔗 decimal-literal	10
🔗 hexadecimal-literal	16

The hexadecimal-digits a through f and A through F have decimal values ten through fifteen.

[Example 1:

The number twelve can be written 12, 014, 0XC, or 0b1100.

The integer-literals 1048576, 1'048'576, 0X100000, 0x10'0000, and 0'004'000'000 all have the same value.

— end example]

The type of an integer-literal is the first type in the list in Table 8 corresponding to its optional integer-suffix in which its value can be represented.

Table 8 — Types of integer-literals [tab:lex.icon.type]

🔗 *integer-suffix*	*decimal-literal*	**integer-literal other than decimal-literal**
🔗 none	int	int
🔗	long int	unsigned int
🔗	long long int	long int
🔗		unsigned long int
🔗		long long int
🔗		unsigned long long int
🔗 u or U	unsigned int	unsigned int
🔗	unsigned long int	unsigned long int
🔗	unsigned long long int	unsigned long long int
🔗 l or L	long int	long int
🔗	long long int	unsigned long int
🔗		long long int
🔗		unsigned long long int
🔗 Both u or U	unsigned long int	unsigned long int
🔗 and l or L	unsigned long long int	unsigned long long int
🔗 ll or LL	long long int	long long int
🔗		unsigned long long int
🔗 Both u or U	unsigned long long int	unsigned long long int
🔗 and ll or LL
🔗 z or Z	the signed integer type corresponding	the signed integer type
🔗	to std::size_t ([support.types.layout])	corresponding to std::size_t
🔗		std::size_t
🔗 Both u or U	std::size_t	std::size_t
🔗 and z or Z

Except for integer-literals containing a size-suffix, if the value of an integer-literal cannot be represented by any type in its list and an extended integer type ([basic.fundamental]) can represent its value, it may have that extended integer type.

If all of the types in the list for the integer-literal are signed, the extended integer type is signed.

If all of the types in the list for the integer-literal are unsigned, the extended integer type is unsigned.

If the list contains both signed and unsigned types, the extended integer type may be signed or unsigned.

If an integer-literal cannot be represented by any of the allowed types, the program is ill-formed.

[Note 2:

An integer-literal with a z or Z suffix is ill-formed if it cannot be represented by std::size_t.

— end note]