Iterator defined by data-source now only requires one method: next()

data-cursor.go

@@ -13,19 +13,29 @@ type dataCursor struct {
 	ds          map[string]Functor
 	ctx         ExprContext
 	index       int
+	current any
+	lastErr error
 	resource    any
 	nextFunc    Functor
 	cleanFunc   Functor
 	resetFunc   Functor
-	currentFunc Functor
+//	currentFunc Functor
 }
 
-func NewDataCursor(ctx ExprContext, ds map[string]Functor) (dc *dataCursor) {
+func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *dataCursor) {
 	dc = &dataCursor{
-		ds:    ds,
+		ds:          ds,
-		index: -1,
+		index:       -1,
-		ctx:   ctx.Clone(),
+		current: nil,
+		lastErr: nil,
+		resource:    resource,
+		ctx:         ctx.Clone(),
+		nextFunc:    ds[NextName],
+//		currentFunc: ds[CurrentName],
+		cleanFunc:   ds[CleanName],
+		resetFunc:   ds[ResetName],
 	}
+	dc.Next()
 	return
 }
 
@@ -101,6 +111,7 @@ func (dc *dataCursor) Reset() (success bool, err error) {
 				dc.index = -1
 			}
 			exportObjects(dc.ctx, ctx)
+			dc.Next()
 		} else {
 			err = errInvalidDataSource()
 		}
@@ -129,93 +140,71 @@ func (dc *dataCursor) Clean() (success bool, err error) {
 }
 
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
-	ctx := cloneContext(dc.ctx)
+	if dc.current != nil {
-	if item, err = dc.currentFunc.Invoke(ctx, CurrentName, []any{}); err == nil && item == nil {
+		item = dc.current
+	} else {
 		err = io.EOF
 	}
-	exportObjects(dc.ctx, ctx)
 	return
 }
 
-// func (dc *dataCursor) _Next() (item any, err error) { // must return io.EOF after the last item
-// 	if dc.resource != nil {
-// 		ctx := cloneContext(dc.ctx)
-// 		// fmt.Printf("Entering Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
-// 		if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{dc.resource}); err == nil {
-// 			if item == nil {
-// 				err = io.EOF
-// 			} else {
-// 				dc.index++
-// 			}
-// 		}
-// 		// fmt.Printf("Exiting Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
-// 		exportObjects(dc.ctx, ctx)
-// 		// fmt.Printf("Outer-Ctx [%p]: %s\n", dc.ctx, CtxToString(dc.ctx, 0))
-// 	} else {
-// 		err = errInvalidDataSource()
-// 	}
-// 	return
-// }
-
-// func (dc *dataCursor) _filter(item any) (filterdItem any, err error) {
-// 	if filter, ok := dc.ds[filterName]; ok {
-// 		ctx := cloneContext(dc.ctx)
-// 		filterdItem, err = filter.Invoke(ctx, filterName, []any{item, dc.index})
-// 	} else {
-// 		filterdItem = item
-// 	}
-// 	return
-// }
-
 func (dc *dataCursor) checkFilter(filter Functor, item any) (accepted bool, err error) {
 	var v any
 	var ok bool
 	ctx := cloneContext(dc.ctx)
 	if v, err = filter.Invoke(ctx, FilterName, []any{item, dc.index}); err == nil && v != nil {
 		if accepted, ok = v.(bool); !ok {
-			accepted = true  // NOTE: A non-boolean value that is not nil means the item has been accepted
+			accepted = true // NOTE: A non-boolean value that is not nil means the item has been accepted
 		}
 	}
-	
 	return
 }
+
 func (dc *dataCursor) mapItem(mapper Functor, item any) (mappedItem any, err error) {
 	ctx := cloneContext(dc.ctx)
-	mappedItem, err = mapper.Invoke(ctx, MapName, []any{item, dc.index});
+	mappedItem, err = mapper.Invoke(ctx, MapName, []any{item, dc.index})
 	return
 }
 
-func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
+func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF after the last item
 	var accepted bool
+	if err = dc.lastErr; err != nil {
+		return
+	}
+	current = dc.current
 	if dc.resource != nil {
 		filter := dc.ds[FilterName]
 		mapper := dc.ds[MapName]
-
+		var item any
-		for item == nil && err == nil {
+		for item == nil && dc.lastErr == nil {
 			ctx := cloneContext(dc.ctx)
-			if item, err = dc.nextFunc.Invoke(ctx, NextName, []any{dc.resource}); err == nil {
+			dc.index++
+			if item, dc.lastErr  = dc.nextFunc.Invoke(ctx, NextName, []any{dc.resource, dc.index}); dc.lastErr == nil {
 				if item == nil {
-					err = io.EOF
+					dc.lastErr = io.EOF
 				} else {
-					dc.index++
 					if filter != nil {
-						if accepted, err = dc.checkFilter(filter, item); err != nil || !accepted {
+						if accepted, dc.lastErr = dc.checkFilter(filter, item); dc.lastErr != nil || !accepted {
 							item = nil
 						}
 					}
 					if item != nil && mapper != nil {
-						item, err = dc.mapItem(mapper, item)
+						item, dc.lastErr = dc.mapItem(mapper, item)
 					}
 				}
 			}
 			exportObjects(dc.ctx, ctx)
 		}
+		dc.current = item
+		if dc.lastErr != nil {
+			dc.Clean()
+		}
 	} else {
-		err = errInvalidDataSource()
+		dc.lastErr = errInvalidDataSource()
 	}
 	return
 }
 
 func (dc *dataCursor) Index() int {
-	return dc.index
+	return dc.index-1
 }

operand-iterator.go

@@ -66,8 +66,8 @@ func evalFirstChild(ctx ExprContext, iteratorTerm *term) (value any, err error)
 
 func getDataSourceDict(iteratorTerm *term, firstChildValue any) (ds map[string]Functor, err error) {
 	if dictAny, ok := firstChildValue.(*DictType); ok {
-		requiredFields := []string{CurrentName, NextName}
+		requiredFields := []string{/*CurrentName,*/ NextName}
-		fieldsMask := 0b11
+		fieldsMask := 0b1
 		foundFields := 0
 		ds = make(map[string]Functor)
 		for keyAny, item := range *dictAny {
@@ -108,9 +108,10 @@ func evalIterator(ctx ExprContext, opTerm *term) (v any, err error) {
 	}
 
 	if ds != nil {
-		dc := NewDataCursor(ctx, ds)
+		var dc *dataCursor
 		if initFunc, exists := ds[InitName]; exists && initFunc != nil {
 			var args []any
+			var resource any
 			if len(opTerm.children) > 1 {
 				if args, err = evalTermArray(ctx, opTerm.children[1:]); err != nil {
 					return
@@ -119,17 +120,20 @@ func evalIterator(ctx ExprContext, opTerm *term) (v any, err error) {
 				args = []any{}
 			}
 
-			initCtx := dc.ctx.Clone()
+			initCtx := ctx.Clone()
-			if dc.resource, err = initFunc.Invoke(initCtx, InitName, args); err != nil {
+			if resource, err = initFunc.Invoke(initCtx, InitName, args); err != nil {
 				return
 			}
-			exportObjects(dc.ctx, initCtx)
+			dcCtx := ctx.Clone()
+			exportObjects(dcCtx, initCtx)
+			dc = NewDataCursor(dcCtx, ds, resource)
+			//exportObjects(dc.ctx, initCtx)
 		}
 
-		dc.nextFunc = ds[NextName]
+		// dc.nextFunc = ds[NextName]
-		dc.currentFunc = ds[CurrentName]
+		// dc.currentFunc = ds[CurrentName]
-		dc.cleanFunc = ds[CleanName]
+		// dc.cleanFunc = ds[CleanName]
-		dc.resetFunc = ds[ResetName]
+		// dc.resetFunc = ds[ResetName]
 
 		v = dc
 	} else if list, ok := firstChildValue.(*ListType); ok {

t_expr_test.go

@@ -19,8 +19,8 @@ func TestExpr(t *testing.T) {
 		/*   5 */ {`1 ? {1} : [1+0] {3*(1+1)}`, int64(6), nil},
 		/*   6 */ {`
 		ds={
-			"init":func(end){@end=end; @current=0 but true},
+			"init":func(@end){@current=0 but true},
-			"current":func(){current},
+			//"current":func(){current},
 			"next":func(){
 				((next=current+1) <= end) ? [true] {@current=next but current} :: {nil}
 			}
@@ -32,6 +32,6 @@ func TestExpr(t *testing.T) {
 	}
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 3)
+	//runTestSuiteSpec(t, section, inputs, 6)
 	runTestSuite(t, section, inputs)
 }