Pr/pipe assignment from main

[hughjonesd]

This is a build of R that adds an experimental pipe assignment operator <|>.

LHS <|> RHS is parsed as LHS <- RHS(LHS, ...).

Examples

x <|> sqrt()             # becomes  x <- sqrt(x)
x[item] <|> foo()       # becomes x[item] <- foo(x[item])
x$elem <|> foo()        # becomes  x$elem <- foo(x$elem)
names(x) <|> toupper()  # becomes  names(x) <- toupper(names(x))
x <|> gsub("pattern", "replacement", x = _)
                        # becomes  x <- gsub("pattern", "replacement", x = x)

Arbitrarily complex left hand sides are allowed, including assignment functions and subassignment.

Chaining <|> is not allowed (and would not make sense). The placeholder works, but placeholder use in e.g. _$foo$bar is not.

Rationale

For a detailed rationale, see https://hughjonesd.github.io/case-for-pipe-assignment.html.

The skinny:

• R is pass-by-value and allows complex subassignment
• Often, one wants to simply pass variables, or parts of them, through a function
• This involves repeating oneself
• Pipe assignment can make code clearer by avoiding the repetition

In other words, these:

names(x)[1:5] <|> toupper()
my_data[rows, cols] <|> as.numeric()

may be easier to read (and to write!) than these:

names(x)[1:5] <- toupper(names(x)[1:5])
my_data[rows, cols] <- as.numeric(my_data[rows, cols])

Vibe-coded

Yeah, this was vibe-coded! Claude basically one-shotted the Yacc, which is much beyond my capability.