Opaque context

Similar usage of the term applies for artificial languages such as programming languages and logics. The Cicero-Tully example above can be easily adapted. Use the notation $[t]$ as a quotation that mentions a term $t$. Define a predicate $L$ to the effect that the letters making up a term number six. Then $[x]$ induces an opaque context, or is referentially opaque, because $L([Cicero])$ is true while $L([Tully])$ is false. Programming languages often have richer semantics than logics' semantics of truth and falsity, and so an operator such as $[x]$ may fail to be referentially transparent for other reasons as well.