public override Maybe<Result> VisitBasic_expr(QueryParser.Basic_exprContext context)
{
if (context.ADD() != null)
return VisitAdd(context);
if (context.SUB() != null)
return VisitSub(context);
return VisitFact_expr(context.fact_expr());
}
private Maybe<Result> VisitSub(QueryParser.Basic_exprContext context)
{
var (left, right) = VisitTwo(context);
return left.Zip(right).Bind(tuple => tuple.Item1.Subtract(tuple.Item2).Just());
}
private (Maybe<Result>, Maybe<Result>) VisitTwo(QueryParser.Basic_exprContext context)
{
var left = new BasicExprVisitor(_zmi, _env).Visit(context.basic_expr());
var right = new BasicExprVisitor(_zmi, _env).Visit(context.fact_expr());
return (left, right);
}
/// <summary>
/// Visit a parse tree produced by <see cref="QueryParser.basic_expr"/>.
/// <para>
/// The default implementation returns the result of calling <see cref="AbstractParseTreeVisitor{Result}.VisitChildren(IRuleNode)"/>
/// on <paramref name="context"/>.
/// </para>
/// </summary>
/// <param name="context">The parse tree.</param>
/// <return>The visitor result.</return>
public virtual Result VisitBasic_expr([NotNull] QueryParser.Basic_exprContext context)
{
return(VisitChildren(context));
}
