Make fmt() function more like C's sprintf()

evaluator/builtin_functions_test.go

@@ -177,8 +177,12 @@ func TestFmt(t *testing.T) {
 	tests := []Tests{
 		{`"hello %s".fmt("world")`, "hello world"},
 		{`"hello %s".fmt()`, "hello %!s(MISSING)"},
-		{`"hello %s".fmt(1)`, "hello 1"},
+		{`"hello %s".fmt(1)`, "hello %!s(int=1)"},
 		{`"hello %s".fmt({})`, "hello {}"},
+		{`"hello %d".fmt(1)`, "hello 1"},
+		{`"hello %d".fmt(1.5)`, "hello %!d(float64=1.5)"},
+		{`"hello %f".fmt(1.5)`, "hello 1.500000"},
+		{`"hello %.3f".fmt(1.5)`, "hello 1.500"},
 	}
 
 	testBuiltinFunction(tests, t)

evaluator/functions.go

@@ -1135,7 +1135,7 @@ func fmtFn(tok token.Token, env *object.Environment, args ...object.Object) obje
 	list := []interface{}{}
 
 	for _, s := range args[1:] {
-		list = append(list, s.Inspect())
+		list = append(list, s.Raw())
 	}
 
 	return &object.String{Token: tok, Value: fmt.Sprintf(args[0].(*object.String).Value, list...)}

object/object.go

@@ -57,6 +57,7 @@ type Object interface {
 	Type() ObjectType
 	Inspect() string
 	Json() string
+	Raw() interface{}
 }
 
 // GenerateEqualityString is used to compare
@@ -106,6 +107,13 @@ func (n *Number) IsInt() bool {
 func (n *Number) Json() string       { return n.Inspect() }
 func (n *Number) ZeroValue() float64 { return float64(0) }
 func (n *Number) Int() int           { return int(n.Value) }
+func (n *Number) Raw() interface{} {
+	if n.IsInt() {
+		return int(n.Value)
+	} else {
+		return n.Value
+	}
+}
 
 type Boolean struct {
 	Token token.Token
@@ -115,6 +123,7 @@ type Boolean struct {
 func (b *Boolean) Type() ObjectType { return BOOLEAN_OBJ }
 func (b *Boolean) Inspect() string  { return fmt.Sprintf("%t", b.Value) }
 func (b *Boolean) Json() string     { return b.Inspect() }
+func (b *Boolean) Raw() interface{} { return b.Value }
 
 type Null struct {
 	Token token.Token
@@ -123,6 +132,7 @@ type Null struct {
 func (n *Null) Type() ObjectType { return NULL_OBJ }
 func (n *Null) Inspect() string  { return "null" }
 func (n *Null) Json() string     { return n.Inspect() }
+func (n *Null) Raw() interface{} { return nil }
 
 type ReturnValue struct {
 	Token token.Token
@@ -132,6 +142,7 @@ type ReturnValue struct {
 func (rv *ReturnValue) Type() ObjectType { return RETURN_VALUE_OBJ }
 func (rv *ReturnValue) Inspect() string  { return rv.Value.Inspect() }
 func (rv *ReturnValue) Json() string     { return rv.Inspect() }
+func (rv *ReturnValue) Raw() interface{} { return rv.Value.Raw() }
 
 type Error struct {
 	Message string
@@ -140,6 +151,7 @@ type Error struct {
 func (e *Error) Type() ObjectType { return ERROR_OBJ }
 func (e *Error) Inspect() string  { return "ERROR: " + e.Message }
 func (e *Error) Json() string     { return e.Inspect() }
+func (e *Error) Raw() interface{} { return e.Message }
 
 type BreakError struct {
 	Error
@@ -182,7 +194,8 @@ func (f *Function) Inspect() string {
 	return out.String()
 }
 
-func (f *Function) Json() string { return f.Inspect() }
+func (f *Function) Json() string     { return f.Inspect() }
+func (f *Function) Raw() interface{} { return f.Inspect() }
 
 // The String is a special fella.
 //
@@ -224,6 +237,7 @@ type String struct {
 func (s *String) Type() ObjectType  { return STRING_OBJ }
 func (s *String) Inspect() string   { return s.Value }
 func (s *String) Json() string      { return `"` + strings.ReplaceAll(s.Inspect(), `"`, `\"`) + `"` }
+func (s *String) Raw() interface{}  { return s.Value }
 func (s *String) ZeroValue() string { return "" }
 func (s *String) HashKey() HashKey {
 	return HashKey{Type: s.Type(), Value: s.Value}
@@ -315,6 +329,7 @@ type Builtin struct {
 func (b *Builtin) Type() ObjectType { return BUILTIN_OBJ }
 func (b *Builtin) Inspect() string  { return "builtin function" }
 func (b *Builtin) Json() string     { return b.Inspect() }
+func (b *Builtin) Raw() interface{} { return b.Inspect() }
 
 type Array struct {
 	Token    token.Token
@@ -381,7 +396,8 @@ func (ao *Array) Inspect() string {
 	return out.String()
 }
 
-func (ao *Array) Json() string { return ao.Inspect() }
+func (ao *Array) Json() string     { return ao.Inspect() }
+func (ao *Array) Raw() interface{} { return ao.Inspect() }
 
 type HashPair struct {
 	Key   Object
@@ -429,7 +445,8 @@ func (h *Hash) Inspect() string {
 
 	return out.String()
 }
-func (h *Hash) Json() string { return h.Inspect() }
+func (h *Hash) Json() string     { return h.Inspect() }
+func (h *Hash) Raw() interface{} { return h.Inspect() }
 
 // Pretty convoluted logic here we could
 // refactor.