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// Package printer implements printing of acc AST nodes.
package printer
import (
"bytes"
"io"
"os"
"github.com/mmcloughlin/addchain/acc/ast"
"github.com/mmcloughlin/addchain/internal/errutil"
"github.com/mmcloughlin/addchain/internal/print"
)
// String prints the AST and returns resulting string.
func String(n interface{}) (string, error) {
b, err := Bytes(n)
if err != nil {
return "", err
}
return string(b), nil
}
// Bytes prints the AST and returns resulting bytes.
func Bytes(n interface{}) ([]byte, error) {
var buf bytes.Buffer
if err := Fprint(&buf, n); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// Print an AST node to standard out.
func Print(n interface{}) error {
return Fprint(os.Stdout, n)
}
// Fprint writes the AST node n to w.
func Fprint(w io.Writer, n interface{}) error {
p := newprinter(w)
p.node(n)
p.Flush()
return p.Error()
}
type printer struct {
*print.TabWriter
}
func newprinter(w io.Writer) *printer {
return &printer{
TabWriter: print.NewTabWriter(w, 1, 4, 1, ' ', 0),
}
}
func (p *printer) node(n interface{}) {
switch n := n.(type) {
case *ast.Chain:
for _, stmt := range n.Statements {
p.statement(stmt)
}
case ast.Statement:
p.statement(n)
case ast.Expr:
p.expr(n, nil)
default:
p.SetError(errutil.UnexpectedType(n))
}
}
func (p *printer) statement(stmt ast.Statement) {
if len(stmt.Name) > 0 {
p.Printf("%s\t=\t", stmt.Name)
} else {
p.Printf("return\t\t")
}
p.expr(stmt.Expr, nil)
p.NL()
}
func (p *printer) expr(e, parent ast.Expr) {
// Parens required if the precence of this operator is less than its parent.
if parent != nil && e.Precedence() < parent.Precedence() {
p.Printf("(")
p.expr(e, nil)
p.Printf(")")
return
}
switch e := e.(type) {
case ast.Operand:
p.operand(e)
case ast.Identifier:
p.identifier(e)
case ast.Add:
p.add(e)
case ast.Double:
p.double(e)
case ast.Shift:
p.shift(e)
default:
p.SetError(errutil.UnexpectedType(e))
}
}
func (p *printer) add(a ast.Add) {
p.expr(a.X, a)
p.Printf(" + ")
p.expr(a.Y, a)
}
func (p *printer) double(d ast.Double) {
p.Printf("2*")
p.expr(d.X, d)
}
func (p *printer) shift(s ast.Shift) {
p.expr(s.X, s)
p.Printf(" << %d", s.S)
}
func (p *printer) identifier(name ast.Identifier) {
p.Printf("%s", name)
}
func (p *printer) operand(op ast.Operand) {
if op == 0 {
p.Printf("1")
} else {
p.Printf("[%d]", op)
}
}
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