73 lines
1.5 KiB
Go
73 lines
1.5 KiB
Go
// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
|
|
// All rights reserved.
|
|
|
|
// operator-filter.go
|
|
package expr
|
|
|
|
import (
|
|
"fmt"
|
|
"io"
|
|
)
|
|
|
|
//-------- map term
|
|
|
|
func newFilterTerm(tk *Token) (inst *term) {
|
|
return &term{
|
|
tk: *tk,
|
|
children: make([]*term, 0, 2),
|
|
position: posInfix,
|
|
priority: priIterOp,
|
|
evalFunc: evalFilter,
|
|
}
|
|
}
|
|
|
|
func evalFilter(ctx ExprContext, opTerm *term) (v any, err error) {
|
|
var leftValue, rightValue any
|
|
var it Iterator
|
|
var item any
|
|
|
|
if err = opTerm.checkOperands(); err != nil {
|
|
return
|
|
}
|
|
|
|
if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
|
|
return
|
|
}
|
|
|
|
if it, err = NewIterator(leftValue); err != nil {
|
|
return nil, fmt.Errorf("left operand of FILTER must be an iterable data-source; got %s", TypeName(leftValue))
|
|
}
|
|
|
|
values := newListA()
|
|
for item, err = it.Next(); err == nil; item, err = it.Next() {
|
|
ctx.SetVar("_", item)
|
|
ctx.SetVar("_index", it.Index())
|
|
ctx.SetVar("_count", it.Count())
|
|
if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
|
|
if success, valid := ToBool(rightValue); valid {
|
|
if success {
|
|
values.appendItem(item)
|
|
}
|
|
} else {
|
|
err = fmt.Errorf("filter expression must return a boolean or a castable to boolean, got %v [%T]", rightValue, rightValue)
|
|
}
|
|
}
|
|
ctx.DeleteVar("_count")
|
|
ctx.DeleteVar("_index")
|
|
ctx.DeleteVar("_")
|
|
if err != nil {
|
|
break
|
|
}
|
|
}
|
|
if err == io.EOF {
|
|
err = nil
|
|
}
|
|
v = values
|
|
return
|
|
}
|
|
|
|
// init
|
|
func init() {
|
|
registerTermConstructor(SymKwFilter, newFilterTerm)
|
|
}
|