GNU R lazy (non-standard) evaluation

 This GNU R package provides a disciplined approach to non-standard
 evaluation.
 .
 Lazyeval provides principled tools to perform non-standard evaluation
 (NSE) in R. It is helpful for programmin with packages like dplyr and
 ggplot2, or to use a principled way of working with delayed expressions
 in own packages. As the name suggests, non-standard evaluation breaks
 away from the standard evaluation (SE) rules in order to do something
 special.