`%.>%`

dot arrow pipe is a strict pipe with intended semantics:

“

`a %.>% b`

” is to be treated as if the user had written “`{ . <- a; b };`

” with “`%.>%`

” being treated as left-associative.

That is: `%.>%`

does not alter any function arguments that are not explicitly named. `%.>%`

is designed to be explicit and simple.

The following two expressions should be equivalent:

```
library("wrapr")
cos(exp(sin(4)))
```

`## [1] 0.8919465`

`4 %.>% sin(.) %.>% exp(.) %.>% cos(.)`

`## [1] 0.8919465`

The notation is quite powerful as it treats pipe stages as expression parameterized over the variable “`.`

”. This means you do not need to introduce functions to express stages. The following is a valid dot-pipe:

`1:4 %.>% .^2 `

`## [1] 1 4 9 16`

The notation is also very regular in that many variations of expression work as expected. Example:

`5 %.>% sin(.)`

`## [1] -0.9589243`

`5 %.>% base::sin(.)`

`## [1] -0.9589243`

Regularity can be a *big* advantage in teaching and comprehension. Please see “In Praise of Syntactic Sugar” for discussion.

The dot arrow pipe has S3/S4 dispatch (please see “Dot-Pipe: an S3 Extensible Pipe for R”). However as the right-hand side of the pipe is normally held unevaluated, we don’t know the type except in special cases (such as the rigth-hand side being referred to by a name or variable). To force the evaluation of a pipe term, simply wrap it in .().

A detail of R-style pipes is the right argument is held unevalauted (unless it is a name), so we can’t always use the class of the right hand side to dispatch. To work around this we suggest using `.()`

notation, which in the context of the pipe means “evaluate early.” An example is given below:

```
<- function() { sin }
f
# returns f() ignoring dot, not what we want
5 %.>% f()
```

`## function (x) .Primitive("sin")`

```
# evaluates f() early then evaluates result with .-substitution rules
5 %.>% .(f())
```

`## [1] -0.9589243`