19.1 Introduction

Three pillars of tidy evaluation

  1. Quasiquotation
  2. Quosures (chapter 20)
  3. Data masks (Chapter 20)

Quasiquotation = quotation + unquotation

  • Quote. Capture unevaluated expression… (“defuse”)
  • Unquote. Evaluate selections of quoted expression! (“inject”)
  • Functions that use these features are said to use Non-standard evaluation (NSE)
  • Note: related to Lisp macros, and also exists in other languages with Lisp heritage, e.g. Julia

On it’s own, Quasiquotation good for programming, but combined with other tools, important for data analysis.