//! Expression types and creation utilities.
//!
//! This module provides the core expression types for building optimization problems:
//! - `Expr` - The main expression enum representing all expressions
//! - `Shape` - Shape information for expressions
//! - Variable creation via `variable()` and `VariableBuilder`
//! - Constant creation via `constant()` and related functions
// Re-export main types
pub use ;
pub use ;
pub use Shape;
pub use ;