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llr

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llr is a small, work in progress and just for fun clojure-like lisp on top of R’s abstract syntax trees. Expressions are not interpreted, but are translated to R’s AST and then interpreted by the R interpreter.

Most implementation details are sub-optimal, but the focus is on having fun and producing results instead writing perfect code. There are also many bugs and inconsistencies!

Installation

remotes::install_github("dirkschumacher/llr")

Intro

(->
  r/datasets::mtcars
  (r/dplyr::filter (r/base::`>` hp 100))
  (r/dplyr::summarise :count (r/dplyr::n) :mean_mpg (r/mean mpg))
  (r/tibble::as_tibble))
#> # A tibble: 1 x 2
#>   count mean_mpg
#>   <int>    <dbl>
#> 1    23     17.5

Or run it from R

library(llr)
interp <- llr_env$new()
interp$eval("(+ 1 1)")
#> 2

Also see some Advent Of Code solutions in llr.

REPL

It also has a (limited) REPL

interp <- llr_env$new()
interp$repl()

Special forms

Data Types

Lists

; this is a list
'(1 2 3 4 5 6)
; an unquoted list is a function call
(+ 1 2 3 4 5 6)
#> 21

Vectors

[1 2 3 4]
#> [1 2 3 4]

Maps

{:a 1 :b 2}
#> {:a 1 :b 2}

Symbols

x
namespaced.variable/x
:keyword
"character"
10 ; integer
10.42 ; double

Functions

(fn [a b] (+ a b))

(fn this
  ([] 0)
  ([a] a)
  ([a b] (+ a b))
  ([a b & more] (reduce + (concat [a b] more))))

def

def defines a symbol in a namespace and assignes it a name.

(def x 1)
(def plus (fn [a b] (+ a b)))
(plus x x)
#> 2

Meta-data

Symbols and values can hold meta-data. That meta-data needs to be a map at the moment.

(def ^{:const true} x ^{:meta "hello"} [ 1 2 3])
(meta x)
#> {:meta "hello"}

Meta-data on symbols is currently only available to the reader.

Macros

Macros are also supported. Macros are functions bound to a name with meta data {:macro true}.

In a macro you can use syntax-quote <backtick> together with the unquote ~ and unquote-splice ~@ operators.

(defmacro infix [operand1 operator operand2]
  `(~operator ~operand1 ~operand2))
(infix 1 + 1)
#> 2

Recursion

Similar to Clojure llr uses recur to jump to a recursion point currently only defined by loop.

(def is-even 
  (fn [number] 
    (loop [cnt number]
      (if (zero? cnt)
        true
        (if (< cnt 0) false (recur (- cnt 2)))))))
#> `is-even`
(is-even 5001)
#> false
(is-even 5000)
#> true

Namespaces

Every top level definition is part of a namespace

(ns product.lib)
(defn compute [a b] (+ a b))
(ns user)
(product.lib/compute 10 32)
#> 42

Reader Dispatch

The reader switches to a different set of interpretations of the next symbol when reading the character #.

#_ ignores the next form

#_ (r/stop "error")
"Yay"
#> "Yay"

R interop

All symbols starting with the namespace r/ are treated slightly differently. You can use that to refer to external R functions and symbols. In addition keywords are interpreted as named arguments.

(r/set.seed 1)
(def rand-numbers (r/stats::rnorm :n 10))
(r/mean rand-numbers)
#> [1] 0.1322028

Design Goals

Contributing

Code of Conduct

Please note that the llr project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.