If a name does not resolve to anything then it resolves to itself

examples/examples_test.go

@@ -0,0 +1,53 @@
+package examples_test
+
+import (
+	"embed"
+	"fmt"
+	"testing"
+
+	"code.betamike.com/mediocregopher/ginger/gg"
+	"code.betamike.com/mediocregopher/ginger/vm"
+	"github.com/stretchr/testify/assert"
+)
+
+//go:embed *.gg
+var examplesFS embed.FS
+
+func TestAllExamples(t *testing.T) {
+
+	tests := []struct {
+		path string
+		in   vm.Value
+		exp  vm.Value
+	}{
+		{
+			path: "fib.gg",
+			in:   vm.Value{Value: gg.Number(5)},
+			exp:  vm.Value{Value: gg.Number(5)},
+		},
+		{
+			path: "fib.gg",
+			in:   vm.Value{Value: gg.Number(10)},
+			exp:  vm.Value{Value: gg.Number(55)},
+		},
+		{
+			path: "fib.gg",
+			in:   vm.Value{Value: gg.Number(69)},
+			exp:  vm.Value{Value: gg.Number(117669030460994)},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("%s_%v", test.path, test.in), func(t *testing.T) {
+			f, err := examplesFS.Open(test.path)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer f.Close()
+
+			got, err := vm.EvaluateSource(f, test.in, vm.GlobalScope)
+			assert.NoError(t, err)
+			assert.True(t, test.exp.Equal(got), "%v != %v", test.exp, got)
+		})
+	}
+}

vm/function.go

@@ -1,6 +1,7 @@
 package vm
 
 import (
+	"errors"
 	"fmt"
 
 	"code.betamike.com/mediocregopher/ginger/gg"
@@ -79,8 +80,6 @@ func FunctionFromGraph(g *gg.Graph, scope Scope) (Function, error) {
 			return edgeFn(Identity(val)), nil
 		}
 
-		name := *val.Name
-
 		if val.Equal(valNameIn) {
 			return edgeFn(FunctionFunc(func(inArg Value) Value {
 				return inArg
@@ -89,15 +88,17 @@ func FunctionFromGraph(g *gg.Graph, scope Scope) (Function, error) {
 
 		edgesIn := g.ValueIns(val.Value)
 
+		name := *val.Name
+
 		if l := len(edgesIn); l == 0 {
-
-			val, err := scope.Resolve(name)
-
-			if err != nil {
+			resolvedVal, err := scope.Resolve(name)
+			if errors.Is(err, ErrNameNotDefined) {
+				return edgeFn(Identity(val)), nil
+			} else if err != nil {
 				return nil, fmt.Errorf("resolving name %q from the outer scope: %w", name, err)
 			}
 
-			return edgeFn(Identity(val)), nil
+			return edgeFn(Identity(resolvedVal)), nil
 
 		} else if l != 1 {
 			return nil, fmt.Errorf("resolved name %q to %d input edges, rather than one", name, l)
@@ -123,7 +124,6 @@ func FunctionFromGraph(g *gg.Graph, scope Scope) (Function, error) {
 				return valToEdgeFn(Value{Value: ggVal})
 			},
 			func(ggEdgeVal gg.OptionalValue, inEdgeFns []edgeFn) (edgeFn, error) {
-
 				if ggEdgeVal.Equal(valNameIf.Value) {
 
 					if len(inEdgeFns) != 3 {
@@ -177,11 +177,7 @@ func FunctionFromGraph(g *gg.Graph, scope Scope) (Function, error) {
 
 				if edgeVal.Graph != nil {
 
-					opFromGraph, err := FunctionFromGraph(
-						edgeVal.Graph,
-						scope.NewScope(),
-					)
-
+					opFromGraph, err := FunctionFromGraph(edgeVal.Graph, scope)
 					if err != nil {
 						return nil, fmt.Errorf("compiling graph to operation: %w", err)
 					}
@@ -198,7 +194,7 @@ func FunctionFromGraph(g *gg.Graph, scope Scope) (Function, error) {
 					})), nil
 				}
 
-				// the edgeVal is not an Function at compile time, and so
+				// the edgeVal is not a Function at compile time, and so
 				// it must become one at runtime. We must resolve edgeVal to an
 				// edgeFn as well (edgeEdgeFn), and then at runtime that is
 				// given the inArg and (hopefully) the resultant Function is
@@ -217,8 +213,7 @@ func FunctionFromGraph(g *gg.Graph, scope Scope) (Function, error) {
 					if runtimeEdgeVal.Graph != nil {
 
 						runtimeFn, err := FunctionFromGraph(
-							runtimeEdgeVal.Graph,
-							scope.NewScope(),
+							runtimeEdgeVal.Graph, scope,
 						)
 
 						if err != nil {

vm/scope.go

@@ -1,18 +1,19 @@
 package vm
 
 import (
-	"fmt"
+	"errors"
 )
 
+// ErrNameNotDefined is returned from Scope.Resolve when a name could not be
+// resolved within a Scope.
+var ErrNameNotDefined = errors.New("not defined")
+
 // Scope encapsulates a set of name->Value mappings.
 type Scope interface {
 
-	// Resolve accepts a name and returns an Value.
+	// Resolve accepts a name and returns an Value, or returns
+	// ErrNameNotDefined.
 	Resolve(string) (Value, error)
-
-	// NewScope returns a new Scope which sub-operations within this Scope
-	// should use for themselves.
-	NewScope() Scope
 }
 
 // ScopeMap implements the Scope interface.
@@ -27,17 +28,12 @@ func (m ScopeMap) Resolve(name string) (Value, error) {
 	v, ok := m[name]
 
 	if !ok {
-		return Value{}, fmt.Errorf("%q not defined", name)
+		return Value{}, ErrNameNotDefined
 	}
 
 	return v, nil
 }
 
-// NewScope returns the ScopeMap as-is.
-func (m ScopeMap) NewScope() Scope {
-	return m
-}
-
 type scopeWith struct {
 	Scope // parent
 	name  string

vm/vm.go

@@ -114,7 +114,7 @@ func EvaluateSource(opSrc io.Reader, input Value, scope Scope) (Value, error) {
 		return Value{}, errors.New("value must be a graph")
 	}
 
-	fn, err := FunctionFromGraph(v.Value.Graph, scope.NewScope())
+	fn, err := FunctionFromGraph(v.Value.Graph, scope)
 	if err != nil {
 		return Value{}, err
 	}

vm/vm_test.go

@@ -32,10 +32,16 @@ func TestVM(t *testing.T) {
 			in:     Value{Value: gg.Number(1)},
 			expErr: "name !foo cannot start with a '!'",
 		},
+		{
+			src: `{foo = bar; !out = foo;}`,
+			in:  Value{},
+			exp: Value{Value: gg.Name("bar")},
+		},
 	}
 
 	for i, test := range tests {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			t.Log(test.src)
 			val, err := EvaluateSource(
 				bytes.NewBufferString(test.src), test.in, GlobalScope,
 			)