This help topic is for R version 2.9.0. For the current version of R, try https://stat.ethz.ch/R-manual/R-patched/library/base/html/NumericConstants.html
NumericConstants {base}R Documentation

Numeric Constants

Description

How R parses numeric constants.

Details

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.

See Also

Syntax.

Quotes for the parsing of character constants,

Examples

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 :-)

[Package base version 2.9.0 ]