tweaks

README.md

@@ -36,6 +36,7 @@ func main() {
 
 - Andrew Davison ([@infradig](https://github.com/infradig)) and other contributors to [Trealla Prolog](https://github.com/trealla-prolog/trealla).
 - Jos De Roo ([@josd](https://github.com/josd)) for test cases and encouragement.
+- Aram Panasenco ([@panasenco](https://github.com/panasenco)) for his JSON library.
 
 ## License
 

bench_test.go

@@ -20,19 +20,17 @@ func BenchmarkQuery(b *testing.B) {
 	}
 }
 
-// func BenchmarkTak(b *testing.B) {
-// 	pl, err := New(WithPreopenDir("./testdata"))
-// 	if err != nil {
-// 		b.Fatal(err)
-// 	}
-// 	ctx := context.Background()
-// 	b.ResetTimer()
-// 	for i := 0; i < b.N; i++ {
-// 		ans, err := pl.Query(ctx, "consult(tak), run")
-// 		println("a")
-// 		_ = ans
-// 		if err != nil {
-// 			b.Fatal(err)
-// 		}
-// 	}
-// }
+func BenchmarkTak(b *testing.B) {
+	pl, err := New(WithPreopenDir("testdata"))
+	if err != nil {
+		b.Fatal(err)
+	}
+	ctx := context.Background()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := pl.Query(ctx, "consult('testdata/tak'), run")
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}

prolog_test.go

@@ -70,3 +70,25 @@ func TestQuery(t *testing.T) {
 	}
 
 }
+
+func TestThrow(t *testing.T) {
+	pl, err := New(WithPreopenDir("testdata"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := context.Background()
+	ans, err := pl.Query(ctx, `throw(ball).`)
+	if err != nil {
+		// TODO: might want to make this an error in the future instead of a status
+		t.Fatal(err)
+	}
+
+	if ans.Result != ResultError {
+		t.Error("unexpected result. want:", ResultError, "got:", ans.Result)
+	}
+
+	if ans.Error != "ball" {
+		t.Error(`unexpected error value. want: "ball" got:`, ans.Error)
+	}
+}

term.go

@@ -9,6 +9,7 @@ import (
 )
 
 // Term is a Prolog term.
+//
 // One of the following types:
 //	- string
 //	- int64
@@ -21,6 +22,7 @@ type Term = any
 // In other words, it's one answer to a query.
 type Solution map[string]Term
 
+// UnmarshalJSON implements the encoding/json.Marshaler interface.
 func (sol *Solution) UnmarshalJSON(bs []byte) error {
 	var raws map[string]json.RawMessage
 	dec := json.NewDecoder(bytes.NewReader(bs))
@@ -138,6 +140,12 @@ type Compound struct {
 	Args []Term
 }
 
+// Indicator returns the procedure indicator of this compound in Functor/Arity format.
+func (c Compound) Indicator() string {
+	// TODO: escape
+	return fmt.Sprintf("%s/%d", c.Functor, len(c.Args))
+}
+
 // String returns a Prolog-ish representation of this Compound.
 func (c Compound) String() string {
 	if len(c.Args) == 0 {

term_test.go

@@ -11,4 +11,8 @@ func TestCompound(t *testing.T) {
 	if c0.String() != want {
 		t.Errorf("bad string. want: %v got: %v", want, c0.String())
 	}
+	pi := "foo/2"
+	if c0.Indicator() != pi {
+		t.Errorf("bad indicator. want: %v got: %v", pi, c0.Indicator())
+	}
 }

trealla.go

@@ -13,6 +13,8 @@ import (
 //go:embed tpl.wasm
 var tplWASM []byte
 
+var wasmEngine = wasmer.NewEngine()
+
 // Prolog is a Prolog interpreter.
 type Prolog interface {
 	// Query executes a query.
@@ -30,7 +32,7 @@ type prolog struct {
 
 // New creates a new Prolog interpreter.
 func New(opts ...Option) (Prolog, error) {
-	pl, err := newEngine()
+	pl, err := newProlog()
 	if err != nil {
 		return nil, err
 	}
@@ -40,15 +42,14 @@ func New(opts ...Option) (Prolog, error) {
 	return pl, nil
 }
 
-func newEngine() (*prolog, error) {
-	engine := wasmer.NewEngine()
-	store := wasmer.NewStore(engine)
+func newProlog() (*prolog, error) {
+	store := wasmer.NewStore(wasmEngine)
 	module, err := wasmer.NewModule(store, tplWASM)
 	if err != nil {
 		return nil, err
 	}
 	return &prolog{
-		engine: engine,
+		engine: wasmEngine,
 		store:  store,
 		module: module,
 	}, nil
@@ -100,6 +101,7 @@ type Answer struct {
 	Output string
 }
 
+// Result is the status of a query answer.
 type Result string
 
 // Result values.
@@ -142,7 +144,8 @@ func (pl *prolog) ask(ctx context.Context, query string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	ch := make(chan error, 1)
+
+	ch := make(chan error, 2)
 	go func() {
 		defer func() {
 			if ex := recover(); ex != nil {
@@ -155,7 +158,7 @@ func (pl *prolog) ask(ctx context.Context, query string) (string, error) {
 
 	select {
 	case <-ctx.Done():
-		return "", fmt.Errorf("trealla: canceled: %x", ctx.Err())
+		return "", fmt.Errorf("trealla: canceled: %w", ctx.Err())
 	case err := <-ch:
 		stdout := string(wasiEnv.ReadStdout())
 		return stdout, err
@@ -171,7 +174,7 @@ func escapeQuery(query string) string {
 type Option func(*prolog)
 
 // WithPreopenDir sets the preopen directory to dir, granting access to it. Calling this again will overwrite it.
-// More or less equivalent to WithMapDir(dir, dir).
+// More or less equivalent to `WithMapDir(dir, dir)`.
 func WithPreopenDir(dir string) Option {
 	return func(pl *prolog) {
 		pl.preopen = dir