elliotchance/gedcom

package q

// Statement represents a single discreet operation in the engine.
type Statement struct {
    // VariableName must be unique amongst other variables and must not be the
    // name of an existing function. The name is also allow to be empty which
    // means that the result cannot be referenced in other expressions.
    VariableName string

    // Expressions are separated by pipes. The result of each evaluated
    // expressions is used as the input to the next expressions. The input value
    // for the first expression is the gedcom.Document.
    Expressions []Expression
}

// Evaluate executes all of the expressions and returns the final result.
func (v *Statement) Evaluate(engine *Engine, input interface{}) (interface{}, error) {
    var err error

    for _, expression := range v.Expressions {
        input, err = expression.Evaluate(engine, input, nil)

        if err != nil {
            return nil, err
        }
    }

    return input, nil
}