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. Except for selected parts which we do want to evaluate! (“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