exprh

Exprh is a fictional notation and data format designed to represent hierarchical expressions for symbolic computation and data interchange. It encodes operator-operand trees in a compact, human-readable form and supports optional metadata that can describe type information, provenance, or constraints. Although fictional, exprh is intended as a concise reference for discussing tree-structured expressions in theoretical and educational contexts.

Syntax and examples: An exprh expression is written as operator(arg1, arg2, ...). Arguments may be primitives, variables, or nested exprh expressions. Example: add(3, mul(2, x)) represents the sum of 3 and the product of 2 and x. Metadata can be attached after an expression using curly braces, for example: add(3, mul(2, x)) {type: numeric, provenance: example1}.

Semantics: Evaluators may operate in numeric mode when all operands are numbers, substituting symbolic representations otherwise. Expression simplification rules can be defined externally. Exprh implementations are typically designed to preserve structural information to enable traceability, substitution, and rewriting.

History and usage: Conceptual and used in teaching to illustrate tree-structured expressions. It has no single formal standard; several toy libraries and teaching tools implement variants of the syntax.

See also: s-expression, Lisp, abstract syntax tree, expression tree, symbolic algebra.