Add support for macros, add defn to core.lisp

CHANGELOG.md

@@ -1,5 +1,17 @@
 # Changelog
 
+## v0.3.0 (2020-02-22)
+
+* Add support for macros through `macro*` special form.
+* Use Macro support to add `defn` and `defmacro` macros.
+* Rewrite `core.lisp` with `defn` macro.
+
+## v0.2.3 (2020-02-22)
+
+* Add support for custom special forms through `SpecialForm` type.
+* Update package documentation.
+* Remove all type specific functions in favour generic slang core.
+
 ## v0.2.2 (2020-02-21)
 
 * Add type init through Type.Invoke() method

examples/core.lisp

@@ -1,57 +1,57 @@
 (ns 'core)
 
-(def nil? (fn* nil? [arg]
-    (= nil arg)))
+(def fn
+    (macro* fn
+        ([& decl] (cons 'fn* decl))))
 
-(def empty? (fn* empty? [coll]
+(def defn (macro* defn [name & fdecl]
+    (let* [func (cons 'fn (cons name fdecl))]
+    `(def ~name ~func))))
+
+(def defmacro (macro* defmacro [name & mdecl]
+    (let* [macro (cons 'macro* (cons name mdecl))]
+    `(def ~name ~macro))))
+
+(defn nil? [arg] (= nil arg))
+
+(defn empty? [coll]
     (if (nil? coll)
         true
-        (nil? (first coll)))))
+        (nil? (first coll))))
+
+; Type check functions
+(defn same-type? [a b] (= (type a) (type b)))
+(defn seq? [arg] (impl? arg types/Seq))
+(defn set? [arg] (same-type? #{} arg))
+(defn list? [arg] (same-type? () arg))
+(defn vector? [arg] (same-type? [] arg))
+(defn int? [arg] (same-type? 0 arg))
+(defn float? [arg] (same-type? 0.0 arg))
+(defn boolean? [arg] (same-type? true arg))
+(defn string? [arg] (same-type? "" arg))
+(defn keyword? [arg] (same-type? :specimen arg))
+(defn symbol? [arg] (same-type? 'specimen arg))
 
-(def true? (fn* true? [arg]
+; Type initialization functions
+(defn set [coll] (apply-seq (type #{}) coll))
+(defn list [& coll] (apply-seq (type ()) coll))
+(defn vector [& coll] (apply-seq (type []) coll))
+(defn int [arg] (to-type arg (type 0)))
+(defn float [arg] (to-type arg (type 0.0)))
+(defn boolean [arg] (true? arg))
+
+(defn true? [arg]
     (if (nil? arg)
         false
         (if (boolean? arg)
             arg
-            true))))
-
-(def not (fn* not [arg]
-    (= false (true? arg))))
+            true)))
 
-(def same-type? (fn* same-type? [a b] (= (type a) (type b))))
+(defn not [arg] (= false (true? arg)))
 
-; Type check functions
-(def seq? (fn* seq? [arg] (impl? arg types/Seq)))
-(def set? (fn* set? [s] (same-type? #{} s)))
-(def list? (fn* list? [s] (same-type? () s)))
-(def vector? (fn* vector? [s] (same-type? [] s)))
-(def int? (fn* int? [arg] (same-type? 0 arg)))
-(def float? (fn* float? [arg] (same-type? 0.0 arg)))
-(def boolean? (fn* boolean? [arg] (same-type? true arg)))
-(def string? (fn* string? [arg] (same-type? "" arg)))
-(def keyword? (fn* keyword? [arg] (same-type? :keyword arg)))
-(def symbol? (fn* symbol? [arg] (same-type? 'sample arg)))
-
-; Type initialization functions
-(def set (fn* set [s] (apply-seq (type #{}) s)))
-(def list (fn* list [& args] (realize args)))
-(def vector (fn* list [& args] (realize args)))
-(def int (fn* int [arg] (to-type arg (type 0))))
-(def float (fn* float [arg] (to-type arg (type 0.0))))
-(def boolean (fn* boolean [arg] (true? arg)))
-
-(def defn (fn* [name args & body]
-    (do
-        (if (not (symbol? name))
-            (throw "name must be symbol, not " (type name)))
-        (if (not (vector? args))
-            (throw "args must be a vector, not " (type args)))
-        (let* [f (concat `(fn* ~name ~args) body)]
-            (eval `(def ~name ~f))))))
-
-(def last (fn* last [coll]
+(defn last [coll]
     (let* [v   (first coll)
-          rem (next coll)]
+           rem (next coll)]
         (if (nil? rem)
             v
-            (last (next coll))))))
+            (last (next coll)))))

examples/slang_test.lisp

@@ -116,6 +116,6 @@
 (def sum-through-let (let* [numbers [1 2 3 4 5]]
                         (do (println "Numbers: " numbers)
                             (let* [sum (apply-seq + numbers)]
-                                (println "Sum of numbers: " numbers)
+                                (println "Sum of numbers: " sum)
                                 sum))))
 (assert (= (+ 1 2 3 4 5) sum-through-let))

func.go

@@ -18,6 +18,20 @@ func (multiFn MultiFn) Eval(_ Scope) (Value, error) {
 	return multiFn, nil
 }
 
+// Expand executes the macro body and returns the result of the expansion.
+func (multiFn MultiFn) Expand(scope Scope, args []Value) (Value, error) {
+	fn, err := multiFn.selectMethod(args)
+	if err != nil {
+		return nil, err
+	}
+
+	if !multiFn.IsMacro {
+		return &fn, nil
+	}
+
+	return fn.Invoke(scope, args...)
+}
+
 func (multiFn MultiFn) String() string {
 	var sb strings.Builder
 	for _, fn := range multiFn.Methods {
@@ -30,18 +44,18 @@ func (multiFn MultiFn) String() string {
 
 // Invoke dispatches the call to a method based on number of arguments.
 func (multiFn MultiFn) Invoke(scope Scope, args ...Value) (Value, error) {
-	fn, err := multiFn.selectMethod(args)
-	if err != nil {
-		return nil, err
-	}
-
 	if multiFn.IsMacro {
-		v, err := fn.Invoke(scope, args...)
+		form, err := multiFn.Expand(scope, args)
 		if err != nil {
 			return nil, err
 		}
 
-		return Eval(scope, v)
+		return form.Eval(scope)
+	}
+
+	fn, err := multiFn.selectMethod(args)
+	if err != nil {
+		return nil, err
 	}
 
 	argVals, err := evalValueList(scope, args)

slang/core.go

@@ -119,13 +119,13 @@ func Next(seq sabre.Seq) sabre.Value {
 // Cons inserts the first argument as first element in the second seq argument
 // and returns.
 func Cons(v sabre.Value, seq sabre.Seq) sabre.Value {
-	return seq.Cons(v)
+	return Realize(seq.Cons(v))
 }
 
 // Conj appends the second argument as last element in the first seq argument
 // and returns.
 func Conj(seq sabre.Seq, args ...sabre.Value) sabre.Value {
-	return seq.Conj(args...)
+	return Realize(seq.Conj(args...))
 }
 
 // ThreadFirst threads the expressions through forms by inserting result of

slang/slang.go

@@ -195,6 +195,7 @@ func BindAll(scope sabre.Scope) error {
 		"core/def":          sabre.Def,
 		"core/if":           sabre.If,
 		"core/fn*":          sabre.Lambda,
+		"core/macro*":       sabre.Macro,
 		"core/let*":         sabre.Let,
 		"core/quote":        sabre.SimpleQuote,
 		"core/syntax-quote": sabre.SyntaxQuote,

specials.go

@@ -18,7 +18,14 @@ var (
 	// (fn* name? [arg*] expr*) or (fn* name? ([arg]* expr*)+)
 	Lambda = SpecialForm{
 		Name:  "fn*",
-		Parse: parseLambda,
+		Parse: fnParser(false),
+	}
+
+	// Macro defines an anonymous function and returns. Must have the form
+	// (macro* name? [arg*] expr*) or (fn* name? ([arg]* expr*)+)
+	Macro = SpecialForm{
+		Name:  "macro*",
+		Parse: fnParser(true),
 	}
 
 	// Let implements the (let [binding*] expr*) form. expr are evaluated
@@ -54,48 +61,52 @@ var (
 	}
 )
 
-func parseLambda(scope Scope, forms []Value) (*Fn, error) {
-	if len(forms) < 1 {
-		return nil, fmt.Errorf("insufficient args (%d) for 'fn'", len(forms))
-	}
+func fnParser(isMacro bool) func(scope Scope, forms []Value) (*Fn, error) {
+	return func(scope Scope, forms []Value) (*Fn, error) {
+		if len(forms) < 1 {
+			return nil, fmt.Errorf("insufficient args (%d) for 'fn'", len(forms))
+		}
 
-	nextIndex := 0
-	def := MultiFn{}
+		nextIndex := 0
+		def := MultiFn{
+			IsMacro: isMacro,
+		}
 
-	name, isName := forms[nextIndex].(Symbol)
-	if isName {
-		def.Name = name.String()
-		nextIndex++
-	}
+		name, isName := forms[nextIndex].(Symbol)
+		if isName {
+			def.Name = name.String()
+			nextIndex++
+		}
 
-	return &Fn{
-		Func: func(_ Scope, args []Value) (Value, error) {
-			_, isList := forms[nextIndex].(*List)
-			if isList {
-				for _, arg := range forms[nextIndex:] {
-					spec, isList := arg.(*List)
-					if !isList {
-						return nil, fmt.Errorf("expected arg to be list, not %s",
-							reflect.TypeOf(arg))
+		return &Fn{
+			Func: func(_ Scope, args []Value) (Value, error) {
+				_, isList := forms[nextIndex].(*List)
+				if isList {
+					for _, arg := range forms[nextIndex:] {
+						spec, isList := arg.(*List)
+						if !isList {
+							return nil, fmt.Errorf("expected arg to be list, not %s",
+								reflect.TypeOf(arg))
+						}
+
+						fn, err := makeFn(scope, spec.Values)
+						if err != nil {
+							return nil, err
+						}
+
+						def.Methods = append(def.Methods, *fn)
 					}
-
-					fn, err := makeFn(scope, spec.Values)
+				} else {
+					fn, err := makeFn(scope, forms[nextIndex:])
 					if err != nil {
 						return nil, err
 					}
-
 					def.Methods = append(def.Methods, *fn)
 				}
-			} else {
-				fn, err := makeFn(scope, forms[nextIndex:])
-				if err != nil {
-					return nil, err
-				}
-				def.Methods = append(def.Methods, *fn)
-			}
-			return def, def.validate()
-		},
-	}, nil
+				return def, def.validate()
+			},
+		}, nil
+	}
 }
 
 func parseLet(scope Scope, args []Value) (*Fn, error) {
@@ -277,6 +288,9 @@ func analyze(scope Scope, form Value) error {
 	case *List:
 		return f.parse(scope)
 
+	case String:
+		return nil
+
 	case Seq:
 		return analyzeSeq(scope, f)
 	}