utility function for multiple assignment

1 files changed, 42 insertions, 0 deletions

diff --git a/R/util.R b/R/util.R
new file mode 100644
index 0000000..bb2066e
--- /dev/null
+++ b/R/util.R
@@ -0,0 +1,42 @@
+# Generic form
+'%=%' = function(l, r, ...) UseMethod('%=%')
+
+# Binary Operator
+'%=%.lbunch' = function(l, r, ...) {
+  Envir = as.environment(-1)
+  
+  if (length(r) > length(l))
+    warning("RHS has more args than LHS. Only first", length(l), "used.")
+  
+  if (length(l) > length(r))  {
+    warning("LHS has more args than RHS. RHS will be repeated.")
+    r <- extendToMatch(r, l)
+  }
+  
+  for (II in 1:length(l)) {
+    do.call('<-', list(l[[II]], r[[II]]), envir=Envir)
+  }
+}
+
+# Used if LHS is larger than RHS
+extendToMatch <- function(source, destin) {
+  s <- length(source)
+  d <- length(destin)
+  
+  # Assume that destin is a length when it is a single number and source is not
+  if(d==1 && s>1 && !is.null(as.numeric(destin)))
+    d <- destin
+  
+  dif <- d - s
+  if (dif > 0) {
+    source <- rep(source, ceiling(d/s))[1:d]
+  }
+  return (source)
+}
+
+# Grouping the left hand side
+g = function(...) {
+  List = as.list(substitute(list(...)))[-1L]
+  class(List) = 'lbunch'
+  return(List)
+}
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