ConceptFresh variableModified just nowProperties 4Hide BooksChapter 1. Abstract syntax JourneyProgramming Language Theory Statusreviewing Tagssemanticssyntax grammarGiven a set of variable X\mathcal{X}X, a Variable v∉Xv \notin \mathcal{X}v∈/X. Previous in ConceptsFresh renamingNext in Concepts Fresh variable abstract syntax tree ast