Add a generic caching function

util.R

@@ -0,0 +1,29 @@
+library(rlog)
+
+#' Run a function caching the result on the file system.
+#'
+#' The function will be called with the appended arguments. The [`id`] argument
+#' will be used to identify the cache file on the file system and in log
+#' messages.
+run_cached <- function(id, func, ...) {
+    if (!dir.exists("cache")) {
+        dir.create("cache")
+    }
+
+    cache_file <- paste("cache/", id, ".rds", sep = "")
+
+    if (file.exists(cache_file)) {
+        log_info(sprintf("Loading %s from cache", id))
+
+        # If the cache file exists, we restore the data from it.
+        readRDS(cache_file)
+    } else {
+        # If the cache file doesn't exist, we have to do the computation.
+        data <- func(...)
+
+        # The results are cached for the next run.
+        saveRDS(data, cache_file)
+
+        data
+    }
+}