152 lines
3.2 KiB
Go
152 lines
3.2 KiB
Go
// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// operator-cat.go
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package expr
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import (
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"fmt"
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"io"
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"git.portale-stac.it/go-pkg/expr/kern"
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"git.portale-stac.it/go-pkg/expr/scan"
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)
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//-------- cat term
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func newCatTerm(tk *scan.Token) (inst *scan.Term) {
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return &scan.Term{
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Tk: *tk,
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Children: make([]*scan.Term, 0, 2),
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Position: scan.PosInfix,
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Priority: scan.PriIterOp,
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EvalFunc: evalCat,
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}
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}
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func evalCat(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
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var leftValue, rightValue any
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var itLeft, itRight kern.Iterator
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// var item any
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var ok bool
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if err = opTerm.CheckOperands(); err != nil {
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return
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}
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if leftValue, err = opTerm.Children[0].Compute(ctx); err != nil {
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return
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}
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if rightValue, err = opTerm.Children[1].Compute(ctx); err != nil {
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return
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}
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if itLeft, ok = leftValue.(kern.Iterator); !ok {
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if itLeft, err = NewIterator(ctx, leftValue, nil); err != nil {
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return nil, fmt.Errorf("left operand of JOIN must be an iterable data-source; got %s", kern.TypeName(leftValue))
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}
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}
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if itRight, ok = rightValue.(kern.Iterator); !ok {
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if itRight, err = NewIterator(ctx, rightValue, nil); err != nil {
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return nil, fmt.Errorf("right operand of JOIN must be an iterable data-source; got %s", kern.TypeName(rightValue))
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}
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}
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// values := kern.NewListA()
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// for _, it := range []kern.Iterator{itLeft, itRight} {
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// for item, err = it.Next(); err == nil; item, err = it.Next() {
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// values.AppendItem(item)
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// }
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// }
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// if err == io.EOF {
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// err = nil
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// }
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// v = values
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v = newCatIterator(itLeft, itRight)
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return
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}
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const catIteratorType = "cat"
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type catIterator struct {
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kern.IteratorBase
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itLeft kern.Iterator
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itRight kern.Iterator
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itCurrent kern.Iterator
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}
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func newCatIterator(itLeft, itRight kern.Iterator) (it *catIterator) {
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it = &catIterator{
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IteratorBase: kern.IteratorBase{},
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itLeft: itLeft,
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itRight: itRight,
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itCurrent: itLeft,
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}
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it.Reset()
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return
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}
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func (it *catIterator) TypeName() string {
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return catIteratorType
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}
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func (it *catIterator) String() string {
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return fmt.Sprintf("$(%s %s %s)", it.itLeft, catIteratorType, it.itRight)
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}
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func (it *catIterator) Next() (item any, err error) {
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if it.itCurrent == nil {
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err = io.EOF
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} else {
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if item, err = it.itCurrent.Next(); err == nil {
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it.Increment()
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} else if err == io.EOF {
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if it.itCurrent == it.itLeft {
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it.itCurrent = it.itRight
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} else {
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return
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}
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if item, err = it.itCurrent.Next(); err == nil {
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it.Increment()
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} else {
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it.itCurrent = nil
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}
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}
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}
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it.SetCurrent(item)
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return
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}
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// func (it *catIterator) Reset() (err error) {
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// err = it.itLeft.Reset()
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// it.IteratorBase.Reset()
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// return
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// }
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func (it *catIterator) CallOperation(name string, args map[string]any) (v any, err error) {
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switch name {
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case kern.NextName:
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v, err = it.Next()
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// case kern.ResetName:
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// err = it.Reset()
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// case kern.CleanName:
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// err = it.Clean()
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case kern.IndexName:
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v = it.Index()
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case kern.CurrentName:
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v, err = it.Current()
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case kern.CountName:
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v = it.Count()
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default:
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err = kern.ErrNoOperation(name)
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}
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return
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}
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// init
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func init() {
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scan.RegisterTermConstructor(scan.SymKwCat, newCatTerm)
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}
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