Data update

Task/Execute-Brain-/R/execute-brain-.r

@@ -0,0 +1,50 @@
+bf <- function(code) {
+  instructions <- strsplit(code, "")[[1]]
+  tape <- c()
+  visited <- c()
+
+  pset <- function(n) {
+    if (n %in% visited)
+      p <<- n
+    else {
+      visited[length(visited)+1] <<- n
+      tape[as.character(n)] <<- 0
+      pset(n)
+    }
+  }
+
+  bracket <- function(b1, b2, x) {
+    nest <- 1
+    j <- i + x
+    while (nest != 0) {
+      if (instructions[j] == b1)
+        nest <- nest + 1
+      if (instructions[j] == b2)
+        nest <- nest - 1
+      j <- j + x
+    }
+    i <<- j
+  }
+
+  pset(0)
+  i <- 1
+  while (i <= length(instructions)) {
+    p_ <- as.character(p)
+    c <- instructions[i]
+    switch(c,
+           ">" = pset(p + 1),
+           "<" = pset(p - 1),
+           "+" = tape[p_] <- tape[p_] + 1,
+           "-" = tape[p_] <- tape[p_] - 1,
+           "." = cat(intToUtf8(tape[p_])),
+           # TODO: IMPLEMENT ","
+           "[" = if (tape[p_] == 0) {
+                   bracket("[", "]", 1)
+                   i <- i - 1 # off by one error
+                 },
+           "]" = bracket("]", "[", -1))
+    i <- i + 1
+  }
+}
+
+bf("++++++++++[>+>+++>+++++++>++++++++++<<<<-]>>>++.>+.+++++++..+++.<<++.>+++++++++++++++.>.+++.------.--------.<<+.<.")