backup

expression.go

@@ -235,6 +235,11 @@ type Symbol struct {
 	expr Expression
 }
 
+type Param struct {
+	id *Identifier
+	t  Type
+}
+
 func (v *Symbol) Step() (Expression, error) {
 	if v.expr == nil {
 		return nil, fmt.Errorf("unbound symbol %s at %s", v.id, v.id.position)

input.go

@@ -42,12 +42,12 @@ func (in *Input) Seek(i int) {
 	in.index = i
 }
 
-func (in *Input) Take(amount int) *Input {
+func (in *Input) Take(offset int) *Input {
 	var out = &Input{
 		index: 0,
-		input: in.input[in.index : in.index+amount],
+		input: in.input[in.index : in.index+offset],
 	}
-	in.index += amount
+	in.index += offset
 	return out
 }
 
@@ -70,3 +70,27 @@ func (in *Input) Find(open, close *Token) (int, bool) {
 		return 0, false
 	}
 }
+
+func (in *Input) TakeParens(open, close *Token) (*Input, error) {
+	if in.input[in.index].Equals(open) {
+		return nil, noMatch
+	}
+	start := in.index
+	level := 1
+	idx := slices.IndexFunc(in.input[start+1:], func(a Lexeme) bool {
+		switch {
+		case a.Equals(open):
+			level++
+		case a.Equals(close):
+			level--
+			return level == 0
+		}
+		return false
+	})
+	if idx > -1 {
+		_ = in.Take(idx + 1)
+		return &Input{index: 0, input: in.input[start+1 : idx]}, nil
+	} else {
+		return nil, fmt.Errorf("unmatched parenthesis starting at %s", in.Peek(start).Position())
+	}
+}

lex.go

@@ -22,40 +22,44 @@ func (p *position) Position() position {
 	return *p
 }
 
-type Range [2]position
+type (
+	Range [2]position
 
-type token[T comparable] struct {
-	position
-	value T
-}
+	token[T comparable] struct {
+		position
+		value T
+	}
 
-type Lexeme interface {
-	Position() position
-	Equals(Lexeme) bool
-}
+	Lexeme interface {
+		Position() position
+		Equals(Lexeme) bool
+	}
 
-type Id string
+	Id string
 
-type Token token[string]
+	Token token[string]
 
-type IntToken token[int]
+	IntToken token[int]
 
-type FloatToken token[float64]
+	FloatToken token[float64]
 
-type Identifier token[Id]
+	Identifier token[Id]
+)
 
 var (
-	Lparen      = &Token{value: "("}
-	Rparen      = &Token{value: ")"}
-	Space       = &Token{value: " "}
-	Tab         = &Token{value: "\t"}
-	Newline     = &Token{value: "\n"}
-	SingleQuote = &Token{value: "'"}
-	Let         = &Token{value: "let"}
-	LambdaTok   = &Token{value: "lambda"}
-	If          = &Token{value: "if"}
-	TrueTok     = &Token{value: "t"}
-	NilTok      = &Token{value: "nil"}
+	Lparen         = &Token{value: "("}
+	Rparen         = &Token{value: ")"}
+	LsquareBracket = &Token{value: "["}
+	RsquareBracket = &Token{value: "]"}
+	Space          = &Token{value: " "}
+	Tab            = &Token{value: "\t"}
+	Newline        = &Token{value: "\n"}
+	SingleQuote    = &Token{value: "'"}
+	Let            = &Token{value: "let"}
+	LambdaTok      = &Token{value: "lambda"}
+	If             = &Token{value: "if"}
+	TrueTok        = &Token{value: "t"}
+	NilTok         = &Token{value: "nil"}
 )
 
 func (t Token) String() string {
@@ -107,7 +111,7 @@ func (t *Identifier) Equals(a Lexeme) bool {
 
 var matchInt = regexp.MustCompile(`-?\d+`)
 var matchFloat = regexp.MustCompile(`-?\d+\.\d*`)
-var matchIdentifier = regexp.MustCompile(`[^\'() ]+`)
+var matchIdentifier = regexp.MustCompile(`[^\'() \[\]]+`)
 
 func lex(source string) (*Input, error) {
 	var (

main.go

@@ -28,18 +28,27 @@ func fullStep(e Expression) (Expression, error) {
 
 func builtinFunctions(expr Expression) {
 	functions := map[Id]BuiltInFunction{
-		// "quote": {
-		// 	t: &FunctionType{
-		// 		ret: &PrimInteger,
-		// 		params: ,
-		// 	},
-		// 	f: func(e []Expression) (Expression, error) {
-		// 		if len(e) == 1 {
-		// 			return &Quoted{e[0]}, nil
-		// 		}
-		// 		return &Quoted{&List{e}}, nil
-		// 	},
-		// },
+		"+.": {
+			t: &FunctionType{
+				ret:    &PrimFloat,
+				params: []Type{&PrimFloat, &PrimFloat},
+			},
+			f: func(args []Expression) (Expression, error) {
+				var sum FloatValue = 0
+				for _, arg := range args {
+					if !isValue(arg) {
+						panic("not a value")
+					}
+					switch x := arg.(type) {
+					case *FloatValue:
+						sum += *x
+					default:
+						panic("type error")
+					}
+				}
+				return &sum, nil
+			},
+		},
 		"+": {
 			t: &FunctionType{
 				ret:    &PrimInteger,
@@ -61,27 +70,27 @@ func builtinFunctions(expr Expression) {
 				return &sum, nil
 			},
 		},
-		// "-": func(args []Expression) (Expression, error) {
-		// 	v0, ok := args[0].(*IntValue)
-		// 	if !ok {
-		// 		return nil, fmt.Errorf("integer value was expected")
-		// 	}
-		// 	v1, ok := args[1].(*IntValue)
-		// 	if !ok {
-		// 		return nil, fmt.Errorf("integer value was expected")
-		// 	}
-		// 	var result IntValue = (*v0 - *v1)
-		// 	return &result, nil
-		// },
-		// "=": func(args []Expression) (Expression, error) {
-		// 	if reflect.TypeOf(args[0]) != reflect.TypeOf(args[1]) {
-		// 		return nil, fmt.Errorf("unmatched types")
-		// 	}
-		// 	v0 := reflect.ValueOf(args[0])
-		// 	v1 := reflect.ValueOf(args[1])
-		// 	var result BoolValue = BoolValue(v0.Equal(v1))
-		// 	return &result, nil
-		// },
+		"-": {
+			t: &FunctionType{
+				ret:    &PrimInteger,
+				params: []Type{&PrimInteger, &PrimInteger},
+			},
+			f: func(args []Expression) (Expression, error) {
+				var sum IntValue = 0
+				for _, arg := range args {
+					if !isValue(arg) {
+						panic("not a value")
+					}
+					switch x := arg.(type) {
+					case *IntValue:
+						sum += *x
+					default:
+						panic("type error")
+					}
+				}
+				return &sum, nil
+			},
+		},
 	}
 	for id, f := range functions {
 		expr.Substitute(id, &f)

parse.go

@@ -96,6 +96,35 @@ func parseValue(in *Input) (Expression, error) {
 	}
 }
 
+func parseParamList(in *Input) (Expression, error) {
+	list, err := in.TakeParens(Lparen, Rparen)
+	if err != nil {
+		return nil, err
+	}
+	var params []*Symbol
+	for list.Len() > 0 {
+		p, err := list.TakeParens(LsquareBracket, RsquareBracket)
+		if err != nil {
+			return nil, err
+		}
+		if p.Len() != 2 {
+			return nil, fmt.Errorf("expected parameter in the following form: [identifier type]")
+		}
+		id, ok := p.Peek(0).(*Identifier)
+		if !ok {
+			return nil, noMatch
+		}
+		typ, ok := p.Peek(1).(*Identifier)
+		if !ok {
+			return nil, noMatch
+		}
+		params = append(params, &Symbol{
+			id: ,
+		})
+	}
+	return args, nil
+}
+
 func parseList(in *Input) (Expression, error) {
 	openingParens, ok := in.Pop()
 	if !ok {
@@ -192,11 +221,7 @@ func parseLambda(in *Input) (Expression, error) {
 		return nil, fmt.Errorf("unmatched parenthesis starting at %s", openingParens.Position())
 	}
 	decl := in.Take(idx)
-	tok, ok := decl.Pop()
-	if !ok {
-		return nil, noMatch
-	}
-	if !tok.Equals(LambdaTok) {
+	if tok, ok := decl.Pop(); !ok || !tok.Equals(LambdaTok) {
 		return nil, noMatch
 	}
 	l, err := parseList(decl)

type.go

@@ -84,6 +84,12 @@ func (fa *FunctionType) Equal(b Type) bool {
 	return fa.ret.Equal(fb.ret)
 }
 
+// func FromId(id Id) (Type, error) {
+// 	switch id {
+// 	case "integer":
+// 	}
+// }
+
 // func (fa *VariadicListType) Equal(b Type) bool {
 // 	return false
 // }