new operator 'digest'

operator-digest.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-digest.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+//-------- map term
+
+func newDigestTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalDigest,
+	}
+}
+
+func evalDigest(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it Iterator
+	var item, lastValue 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 MAP must be an iterable data-source; got %s", TypeName(leftValue))
+	}
+
+	lastValue = nil
+	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 rightValue == nil {
+				break
+			} else {
+				lastValue = rightValue
+			}
+		}
+		ctx.DeleteVar("_count")
+		ctx.DeleteVar("_index")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = lastValue
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwDigest, newDigestTerm)
+}

symbol-map.go

@@ -137,7 +137,7 @@ func init() {
 		SymKwBut:     {"but", symClassOperator, posInfix},
 		SymKwMap:     {"map", symClassOperator, posInfix},
 		SymKwFilter:  {"filter", symClassOperator, posInfix},
-		// SymKwDigest:  {"digest", symClassOperator, posInfix},
+		SymKwDigest:  {"digest", symClassOperator, posInfix},
 		SymKwFunc:    {"func(", symClassDeclaration, posPrefix},
 		SymKwBuiltin: {"builtin", symClassOperator, posPrefix},
 		SymKwPlugin:  {"plugin", symClassOperator, posPrefix},

symbol.go

@@ -121,7 +121,7 @@ const (
 	SymKwInclude
 	SymKwMap
 	SymKwFilter
-	// SymKwDigest
+	SymKwDigest
 	SymKwNil
 	SymKwUnset
 )
@@ -144,6 +144,6 @@ func init() {
 		"OR":      SymKwOr,
 		"NIL":     SymKwNil,
 		"UNSET":   SymKwUnset,
-		// "DIGEST": SymKwDigest,
+		"DIGEST":  SymKwDigest,
 	}
 }