# Meaning of $\triangleright$ in programming language semantics

What does the symbol "$\triangleright$" mean programming language semantics? I've seen it in the context of datatypes in and the evaluation of expressions in environments.

For example :

$$tenv \triangleright erht \implies tval$$

or

$$tenv[tval/x]\triangleright ebody\implies t\,.$$

Here, $tenv$ is an environment and $ebody$ is the body of some expression.

• @DavidRicherby The context is the one of data types and evaluation into an environment. In the second example tenv is an environment and **ebody ** is the body of an expression – user43288 Dec 7 '16 at 19:12
• This symbol is used in different ways in different contexts in CS, for example in term rewriting, I've seen it represent "is a super-term". Here it sure looks like $e\triangleright t\Rightarrow v$ means "$t$ reduces to $v$ in environment $e$". – cody Dec 7 '16 at 21:14
• @GerardoZinno More generally, whatever you're reading should be telling you what it means (or rather what the whole $- \triangleright - \implies -$ relation means). This notation is not "standardized" in any way. You may find my answer (cs.stackexchange.com/questions/54508/…) useful, and it should help clarify what I mean. – Derek Elkins Dec 8 '16 at 6:46

## 1 Answer

Most probably, in your context, ▹ is just a syntactic separator, meaning "in the environment to the left of ▹, the formula to the right of ▹ holds".

However, ▹ has no fixed meaning in general. I used it myself with completely different definitions.