Celestino Amoroso
1a1a475dd8
This feature is implemented by expansion, not by dedicated operators, e.g. a*=2+x is exapanded as a=a*(2+x)
131 lines
2.5 KiB
Go
131 lines
2.5 KiB
Go
// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// ast.go
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package expr
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import (
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"strings"
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)
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//-------- ast
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type ast struct {
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forest []*term
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root *term
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}
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func NewAst() *ast {
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return &ast{}
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}
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func (expr *ast) TypeName() string {
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return "Expression"
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}
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func (expr *ast) ToForest() {
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if expr.root != nil {
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if expr.forest == nil {
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expr.forest = make([]*term, 0)
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}
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expr.forest = append(expr.forest, expr.root)
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expr.root = nil
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}
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}
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func (expr *ast) String() string {
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var sb strings.Builder
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if expr.root == nil {
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sb.WriteString("(nil)")
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} else {
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expr.root.toString(&sb)
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}
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return sb.String()
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}
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func (expr *ast) addTokens(tokens ...*Token) (err error) {
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for _, tk := range tokens {
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if _, err = expr.addToken(tk); err != nil {
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break
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}
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}
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return
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}
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// func (expr *ast) addToken(tk *Token) (err error) {
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// _, err = expr.addToken2(tk)
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// return
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// }
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func (expr *ast) addToken(tk *Token) (t *term, err error) {
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if t = newTerm(tk); t != nil {
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err = expr.addTerm(t)
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} else {
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err = tk.Errorf("unexpected token %q", tk.String())
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}
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return
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}
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func (expr *ast) addTerm(node *term) (err error) {
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if expr.root == nil {
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expr.root = node
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} else {
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expr.root, err = expr.insert(expr.root, node)
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}
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return
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}
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func (expr *ast) insert(tree, node *term) (root *term, err error) {
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if tree.getPriority() < node.getPriority() {
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root = tree
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if tree.isComplete() {
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var subRoot *term
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last := tree.removeLastChild()
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if subRoot, err = expr.insert(last, node); err == nil {
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subRoot.setParent(tree)
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}
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} else {
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node.setParent(tree)
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}
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} else if !node.isLeaf() {
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root = node
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tree.setParent(node)
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} else {
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err = node.Errorf("two adjacent operators: %q and %q", tree, node)
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}
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return
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}
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func (expr *ast) Finish() {
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if expr.root == nil && expr.forest != nil && len(expr.forest) >= 1 {
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expr.root = expr.forest[len(expr.forest)-1]
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expr.forest = expr.forest[0 : len(expr.forest)-1]
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}
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}
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func (expr *ast) Eval(ctx ExprContext) (result any, err error) {
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expr.Finish()
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if expr.root != nil {
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// initDefaultVars(ctx)
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if expr.forest != nil {
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for _, root := range expr.forest {
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if result, err = root.compute(ctx); err == nil {
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ctx.UnsafeSetVar(ControlLastResult, result)
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} else {
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//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)
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break
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}
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}
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}
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if err == nil {
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if result, err = expr.root.compute(ctx); err == nil {
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ctx.UnsafeSetVar(ControlLastResult, result)
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}
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}
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// } else {
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// err = errors.New("empty expression")
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}
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return
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}
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