R with (x) => x + 1

Modified R grammar file that adds anonymous functions like this:

f <- (x) => x + 1
f(2)
# 3

Install

1. Define the R version:

   export R_VERSION=3.6.3
   

   This is the R version I based the modifications on, so it might not work with other versions.

2. Follow the 'Download and extract R' instructions from https://docs.rstudio.com/resources/install-r-source/

3. Replace the downloaded version of src/main/gram.y with src/main/gram.y from this repo

4. Generate a new parser file:

   bison -d src/main/gram.y -o src/main/gram.c
   

   You should see this output:

   src/main/gram.y: warning: 84 shift/reduce conflicts [-Wconflicts-sr]
   

5. Follow the 'Build and install R' instructions from https://docs.rstudio.com/resources/install-r-source/

   When I did this, I added a couple of lines to the ./configure command:

   ./configure \
       --prefix=/opt/R/${R_VERSION} \
       --enable-memory-profiling \
       --enable-R-shlib \
       --with-blas \
       --with-lapack \
       --with-pcre1 \
       --without-recommended-packages
   

Usage

Run:

/opt/R/${R_VERSION}/bin/R

Play:

f <- (x) => x + 1
g <- (x, y) => x + y
h <- (x = 1) => x + 1
i <- () => 1
f(2)
# 3
g(2, 3)
# 5
h()
# 2
i()
# 1

Check that things haven't broken too much:

# Normal functions
j <- function(x) x + 1
j(2)
# 3
# Normal expressions in parentheses
(1)
# 1
# Normal assignment in parentheses
(y = 5)
y
# 5

Issues

The R grammar is complex and there's a fair chance that these modifications have broken something. Feel free to raise an issue if you find any errors.