Added all source files

ast.go

@@ -0,0 +1,84 @@
+// ast.go
+package expr
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+//-------- ast
+
+type ast struct {
+	root *term
+}
+
+func NewAst() *ast {
+	return &ast{}
+}
+
+func (self *ast) String() string {
+	var sb strings.Builder
+	if self.root == nil {
+		sb.WriteString("(nil)")
+	} else {
+		self.root.toString(&sb)
+	}
+	return sb.String()
+}
+
+func (self *ast) addTokens(tokens ...*Token) (err error) {
+	for _, tk := range tokens {
+		if err = self.addToken(tk); err != nil {
+			break
+		}
+	}
+	return
+}
+
+func (self *ast) addToken(tk *Token) (err error) {
+	if t := newTerm(tk, nil); t != nil {
+		err = self.addTerm(t)
+	} else {
+		err = fmt.Errorf("No term constructor for token %q", tk.String())
+	}
+	return
+}
+
+func (self *ast) addTerm(node *term) (err error) {
+	if self.root == nil {
+		self.root = node
+	} else {
+		self.root, err = self.insert(self.root, node)
+	}
+	return
+}
+
+func (self *ast) insert(tree, node *term) (root *term, err error) {
+	if tree.getPriority() < node.getPriority() {
+		root = tree
+		if tree.isComplete() {
+			var subRoot *term
+			last := tree.removeLastChild()
+			subRoot, err = self.insert(last, node)
+			subRoot.setParent(tree)
+		} else {
+			node.setParent(tree)
+		}
+	} else if !node.isLeaf() {
+		root = node
+		tree.setParent(node)
+	} else {
+		err = fmt.Errorf("two adjacent operators: %q and %q", tree, node)
+	}
+	return
+}
+
+func (self *ast) eval(ctx exprContext) (result any, err error) {
+	if self.root != nil {
+		result, err = self.root.compute(ctx)
+	} else {
+		err = errors.New("empty expression")
+	}
+	return
+}