R: add step4_if_fn_do and step5_tco.

Switch nil from NULL to special class.

1 files changed, 18 insertions, 4 deletions

diff --git a/r/env.r b/r/env.r
index e7ad789..b688b4d 100644
--- a/r/env.r
+++ b/r/env.r
@@ -2,8 +2,22 @@
 
 if(!exists("..types..")) source("types.r")
 
-new.Env <- function(outer=emptyenv()) {
-    structure(new.env(parent=outer), class="Env")
+new.Env <- function(outer=emptyenv(), binds=list(), exprs=list()) {
+    e <- structure(new.env(parent=outer), class="Env")
+
+    if (length(binds) > 0) {
+        for(i in seq(length(binds))) {
+            b <- as.character(binds[[i]])
+            if (b == "&") {
+                e[[as.character(binds[[i+1]])]] <-
+                    slice(exprs, i, length(exprs))
+                break
+            } else {
+                e[[b]] <- exprs[[i]]
+            }
+        }
+    }
+    e
 }
 
 Env.find <- function(e, key) {
@@ -13,7 +27,7 @@ Env.find <- function(e, key) {
     } else if (!identical(parent.env(e), emptyenv())) {
         Env.find(parent.env(e), key)
     } else {
-        NULL
+        nil
     }
 }
 
@@ -26,6 +40,6 @@ Env.set <- function(e, key, val) {
 Env.get <- function(e, key) {
     key <- as.character(key)
     e <- Env.find(e, key)
-    if (is.null(e)) throw(concat("'", key, "' not found"))
+    if (.nil_q(e)) throw(concat("'", key, "' not found"))
     e[[key]]
 }