# Syntax

##### Operator Syntax and Precedence

Outlines R syntax and gives the precedence of operators.

- Keywords
- programming, documentation

##### Details

The following unary and binary operators are defined. They are listed in precedence groups, from highest to lowest.

`:: :::` |
access variables in a namespace |

`$ @` |
component / slot extraction |

`[ [[` |
indexing |

`^` |
exponentiation (right to left) |

`- +` |
unary minus and plus |

`:` |
sequence operator |

`%any%` |
special operators (including `%%` and `%/%` ) |

`* /` |
multiply, divide |

`+ -` |
(binary) add, subtract |

`< > <= >= == !=` |
ordering and comparison |

`!` |
negation |

`& &&` |
and |

`| ||` |
or |

`~` |
as in formulae |

`-> ->>` |
rightwards assignment |

`<- <<-` |
assignment (right to left) |

`=` |
assignment (right to left) |

`?` |
help (unary and binary) |

Within an expression operators of equal precedence are evaluated
from left to right except where indicated. (Note that `=`

is not
necessarily an operator.)

The binary operators `::`

, `:::`

, `$`

and `@`

require
names or string constants on the right hand side, and the first two
also require them on the left.

The links in the **See Also** section cover most other aspects of
the basic syntax.

##### Note

There are substantial precedence differences between R and S. In
particular, in S `?`

has the same precedence as (binary) `+ -`

and `& && | ||`

have equal precedence.

##### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
*The New S Language*.
Wadsworth & Brooks/Cole.

##### See Also

`Arithmetic`

, `Comparison`

, `Control`

,
`Extract`

, `Logic`

,
`NumericConstants`

, `Paren`

,
`Quotes`

, `Reserved`

.

The ‘R Language Definition’ manual.

##### Examples

`library(base)`

```
# NOT RUN {
## Logical AND ("&&") has higher precedence than OR ("||"):
TRUE || TRUE && FALSE # is the same as
TRUE || (TRUE && FALSE) # and different from
(TRUE || TRUE) && FALSE
## Special operators have higher precedence than "!" (logical NOT).
## You can use this for %in% :
! 1:10 %in% c(2, 3, 5, 7) # same as !(1:10 %in% c(2, 3, 5, 7))
## but we strongly advise to use the "!( ... )" form in this case!
## '=' has lower precedence than '<-' ... so you should not mix them
## (and '<-' is considered better style anyway):
# }
# NOT RUN {
## Consequently, this gives a ("non-catchable") error
x <- y = 5 #-> Error in (x <- y) = 5 : ....
# }
```

*Documentation reproduced from package base, version 3.5.1, License: Part of R 3.5.1*