kaz-yos

#' R implementation of `cond` from Lisp
#' allows for arbitrary numbers of conditionals without ugly nested if statements
#' conditionals are entered as pairs of expressions (clauses), 
#' first the expression to be evaluated and second the return value if the expression is true
#' @param ... an even number of expressions as pairs (see example)
#' @param true the `else` expression (Taken from the Lisp (T resultN) see http://www.cis.upenn.edu/~matuszek/LispText/lisp-cond.html)
#' @return The paired value of the first true conditional expression or the value of true
#' @examples
#' x <- runif(1)
#' cond(x < 0.2, "lower tail",

kaz-yos

## Scheme Interpreter in R
## (more R-ish implementation of "lisp.R")

addGlobals <- function(env) {
    procs <- list("+" = sum,
                  "*" = prod,
                  "-" = function(...) Reduce(`-`, list(...)),
                  "/" = function(...) Reduce(`/`, list(...)),
                  "=" = `==`,
                  "eq?" = `==`,

kaz-yos

(defun foldr (f lst)
  (if (null (cdr lst)) (car lst)
      (funcall f (car lst) (foldr f (cdr lst)))))

(defun foldl (f lst)
  (if (null (cdr lst)) (car lst)
      (funcall f (foldl f (butlast lst)) (car (last lst)))))

(defun foldr-tail (f a lst)
  (if (null lst) a