Function validate_constraints 

pub fn validate_constraints(
    constraints: &[Constraint],
    num_atoms: usize,
) -> Result<(), ConstraintError>

Validates constraint specifications for correctness.

Checks that:

• Atom indices are within valid range
• Target values are reasonable
• No duplicate constraints exist

Arguments

• constraints - List of constraints to validate
• num_atoms - Total number of atoms in the system

Returns

Ok(()) if all constraints are valid, Err(ConstraintError) otherwise.