| NumericConstants {base} | R Documentation |
How R parses numeric constants.
R parses numeric constants in its input in a very similar way to C99 floating-point constants.
Inf and NaN are numeric constants (with
typeof(.) "double"). These are recognized ignoring case,
as is infinity as an alternative to Inf.
NA_real_ and NA_integer_ are constants of
types "double" and "integer" representing missing
values. All other numeric constants start with a digit or period and
are either a decimal or hexadecimal constant optionally followed by
L.
Hexadecimal constants start with 0x or 0X followed by
a nonempty sequence from 0-9 a-f A-F . which is interpreted as a
hexadecimal number, optionally followed by a binary exponent. A binary
exponent consists of an P or p followed by an optional
plus or minus sign followed by a non-empty sequence of (decimal)
digits, and indicates multiplication by a power of two. Thus
0x123p456 is 291 \times 2^{456}.
Decimal constants consist of a nonempty sequence of digits possibly
containing a period (the decimal point), optionally followed by a
decimal exponent. A decimal exponent consists of an E or
e followed by an optional plus or minus sign followed by a
non-empty sequence of digits, and indicates multiplication by a power
of ten.
Values which are too large or too small to be representable will
overflow to Inf or underflow to 0.0.
A numeric constant immediately followed by i is regarded as an
imaginary complex number.
An numeric constant immediately followed by L is regarded as an
integer number when possible (and with a warning if it
contains a ".").
Only the ASCII digits 0–9 are recognized as digits, even in languages which have other representations of digits. The ‘decimal separator’ is always a period and never a comma.
Note that a leading plus or minus is not regarded by the parser as part of a numeric constant but as a unary operator applied to the constant.
Syntax.
Quotes for the parsing of character constants,
2.1
typeof(2)
sqrt(1i) # remember elementary math?
utils::str(0xA0)
identical(1L, as.integer(1))
## You can combine the "0x" prefix with the "L" suffix :
identical(0xFL, as.integer(15)) # (with a regard to Fritz :-)