forge: work in progress: control words: if, if-else, leave, repeat

forge/builtins/builtins.go

@@ -9,7 +9,8 @@ type XT = forge.XT
 type FPtr = forge.FPtr
 
 type builtins struct {
-	Add, Body, Code, Comp, Dup, Get, Lit, Mult, New1, Put, Reg, Swap XT
+	Add, Body, Code, Comp, Drop, Dup, Get, If, IfElse, Leave, Lit, Mult,
+	New1, Put, Reg, Repeat, Swap,
 	Var1 XT
 }
 
@@ -36,13 +37,16 @@ func setup(f FE) *builtins {
 		Body:   r("body", func(f FE, _ XT) { f.Push(f.Pop().(XT).Code().New().Next()) }),
 		Code:   r("code", func(f FE, _ XT) { f.Push(f.Code()) }),
 		Comp:   r("comp", func(f FE, _ XT) { f.LatestXT().Code().Append(f.Pop()) }),
+		Drop:   r("drop", func(f FE, _ XT) { f.Pop() }),
 		Dup:    r("dup", func(f FE, _ XT) { f.Push(f.Peek(0)) }),
 		Get:    r("@", func(f FE, _ XT) { f.Push(f.Pop().(FPtr).Value()) }),
+		Leave:  r("leave", func(f FE, _ XT) { f.RPop() }),
 		Lit:    r("lit", func(f FE, _ XT) { f.Push(f.Literal()) }),
 		Mult:   r("*", func(f FE, _ XT) { f.Push(f.PopI() * f.PopI()) }),
 		New1:   r("new1", func(f FE, _ XT) { f.Push(f.NewVar()) }),
 		Put:    r("!", func(f FE, _ XT) { f.Pop().(FPtr).Set(f.Pop()) }),
 		Reg:    r("reg", func(f FE, _ XT) { reg(f) }),
+		Repeat: r("repeat", func(f FE, _ XT) { f.Reset() }),
 		Swap: r("swap", func(f FE, _ XT) {
 			a := f.Pop()
 			b := f.Pop()
@@ -57,6 +61,23 @@ func setup(f FE) *builtins {
 	return &b
 }
 
+func doif(f FE) {
+	ifBranch := f.Literal().(FPtr)
+	if f.Pop().(bool) {
+		f.Call(ifBranch)
+	}
+}
+
+func doifelse(f FE) {
+	ifBranch := f.Literal().(FPtr)
+	elseBranch := f.Literal().(FPtr)
+	if f.Pop().(bool) {
+		f.Call(ifBranch)
+	} else {
+		f.Call(elseBranch)
+	}
+}
+
 func reg(f FE) {
 	f.Register(forge.FCode(f.Pop().(string), f.Pop().(FPtr)))
 }

forge/forge.go

@@ -68,7 +68,7 @@ func (f *forgeEnv) Call(code fptr) *forgeEnv {
 			f.Push(value)
 		}
 	}
-	f.ip = f.rs.Pop().(fptr)
+	f.ip = f.RPop()
 	return f
 }
 
@@ -104,6 +104,14 @@ func (f *forgeEnv) Peek(d int) fitem {
 	return f.ds.Peek(d)
 }
 
+func (f *forgeEnv) RPop() fptr {
+	return f.rs.Pop().(fptr)
+}
+
+func (f *forgeEnv) Reset() fptr {
+	return f.ip.Reset()
+}
+
 func (f *forgeEnv) LatestXT() XT {
 	return f.latestxt
 }