fix: improve parser, compiler and interpreter APIs

Pass a language spec as an argument when create a new parser,
compiler or interpreter.

Also move the REPL code in interpreter package.

4 files changed, 48 insertions, 15 deletions

diff --git a/interpreter/dump_test.go b/interpreter/dump_test.go
index dd172b9..d8fcc55 100644
--- a/interpreter/dump_test.go
+++ b/interpreter/dump_test.go
@@ -4,11 +4,12 @@ import (
 	"testing"
 
 	"github.com/mvertes/parscan/interpreter"
+	"github.com/mvertes/parscan/lang/golang"
 )
 
 func TestDump(t *testing.T) {
 	initProgram := "var a int = 2+1; a"
-	interp := interpreter.NewInterpreter(GoScanner)
+	interp := interpreter.NewInterpreter(golang.GoSpec)
 	r, e := interp.Eval(initProgram)
 	t.Log(r, e)
 	if e != nil {
@@ -24,7 +25,7 @@ func TestDump(t *testing.T) {
 	d := interp.Dump()
 	t.Log(d)
 
-	interp = interpreter.NewInterpreter(GoScanner)
+	interp = interpreter.NewInterpreter(golang.GoSpec)
 	r, e = interp.Eval(initProgram)
 	t.Log(r, e)
 	if e != nil {
diff --git a/interpreter/interpreter.go b/interpreter/interpreter.go
index 06a4bc1..62b593b 100644
--- a/interpreter/interpreter.go
+++ b/interpreter/interpreter.go
@@ -4,25 +4,25 @@ import (
 	"reflect"
 
 	"github.com/mvertes/parscan/compiler"
-	"github.com/mvertes/parscan/scanner"
+	"github.com/mvertes/parscan/lang"
 	"github.com/mvertes/parscan/vm"
 )
 
 const debug = true
 
-// Interpreter represents the state of an interpreter.
-type Interpreter struct {
+// Interp represents the state of an interpreter.
+type Interp struct {
 	*compiler.Compiler
 	*vm.Machine
 }
 
-// NewInterpreter returns a new interpreter state.
-func NewInterpreter(s *scanner.Scanner) *Interpreter {
-	return &Interpreter{compiler.NewCompiler(s), &vm.Machine{}}
+// NewInterpreter returns a new interpreter.
+func NewInterpreter(s *lang.Spec) *Interp {
+	return &Interp{compiler.NewCompiler(s), &vm.Machine{}}
 }
 
-// Eval interprets a src program and return the last produced value if any, or an error.
-func (i *Interpreter) Eval(src string) (res reflect.Value, err error) {
+// Eval evaluates code string and return the last produced value if any, or an error.
+func (i *Interp) Eval(src string) (res reflect.Value, err error) {
 	codeOffset := len(i.Code)
 	dataOffset := 0
 	if codeOffset > 0 {
diff --git a/interpreter/interpreter_test.go b/interpreter/interpreter_test.go
index 800ace5..71c7dd1 100644
--- a/interpreter/interpreter_test.go
+++ b/interpreter/interpreter_test.go
@@ -7,7 +7,6 @@ import (
 
 	"github.com/mvertes/parscan/interpreter"
 	"github.com/mvertes/parscan/lang/golang"
-	"github.com/mvertes/parscan/scanner"
 )
 
 type etest struct {
@@ -15,19 +14,17 @@ type etest struct {
 	skip          bool
 }
 
-var GoScanner *scanner.Scanner
-
 func init() {
 	log.SetFlags(log.Lshortfile)
-	GoScanner = scanner.NewScanner(golang.GoSpec)
 }
 
 func gen(test etest) func(*testing.T) {
 	return func(t *testing.T) {
+		t.Parallel()
 		if test.skip {
 			t.Skip()
 		}
-		interp := interpreter.NewInterpreter(GoScanner)
+		interp := interpreter.NewInterpreter(golang.GoSpec)
 		errStr := ""
 		r, e := interp.Eval(test.src)
 		t.Log(r, e)
diff --git a/interpreter/repl.go b/interpreter/repl.go
new file mode 100644
index 0000000..73af8a7
--- /dev/null
+++ b/interpreter/repl.go
@@ -0,0 +1,35 @@
+package interpreter
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/mvertes/parscan/scanner"
+)
+
+// Repl executes an interactive line oriented Read Eval Print Loop (REPL).
+func (i *Interp) Repl(in io.Reader) (err error) {
+	liner := bufio.NewScanner(in)
+	text, prompt := "", "> "
+	fmt.Print(prompt)
+	for liner.Scan() {
+		text += liner.Text()
+		res, err := i.Eval(text + "\n")
+		switch {
+		case err == nil:
+			if res.IsValid() {
+				fmt.Println(": ", res)
+			}
+			text, prompt = "", "> "
+		case errors.Is(err, scanner.ErrBlock):
+			prompt = ">> "
+		default:
+			fmt.Println("Error:", err)
+			text, prompt = "", "> "
+		}
+		fmt.Print(prompt)
+	}
+	return err
+}