Introduce an Elemser interface.

eval/builtin_func.go

@@ -291,18 +291,18 @@ func ratFn(ec *EvalCtx, arg Value) {
 	out <- r
 }
 
-// unpack takes any number of tables and output their list elements.
+// unpack takes Elemser's from the input and unpack them.
 func unpack(ec *EvalCtx) {
 	in := ec.ports[0].Chan
 	out := ec.ports[1].Chan
 
 	for v := range in {
-		if list, ok := v.(List); !ok {
+		elemser, ok := v.(Elemser)
+		if !ok {
 			throw(ErrInput)
-		} else {
-			for _, e := range *list.inner {
-				out <- e
-			}
+		}
+		for e := range elemser.Elems() {
+			out <- e
 		}
 	}
 }

eval/compile.go

@@ -693,11 +693,11 @@ func variable(qname string, p int) ValuesOp {
 		}
 		value := variable.Get()
 		if splice {
-			list, ok := value.(List)
+			elemser, ok := value.(Elemser)
 			if !ok {
-				ec.errorf(p, "variable $%s is not a list", qname)
+				ec.errorf(p, "variable $%s (kind %s) cannot be spliced", qname, value.Kind())
 			}
-			return *list.inner
+			return collectElems(elemser)
 		}
 		return []Value{value}
 	}

eval/envPathList.go

@@ -8,7 +8,7 @@ import (
 
 // Errors
 var (
-	ErrCanOnlyAssignList          = errors.New("can only assign list")
+	ErrCanOnlyAssignList          = errors.New("can only assign compatible values")
 	ErrPathMustBeString           = errors.New("path must be string")
 	ErrPathCannotContainColonZero = errors.New(`path cannot contain colon or \0`)
 )
@@ -30,13 +30,12 @@ func (epl *EnvPathList) Get() Value {
 }
 
 func (epl *EnvPathList) Set(v Value) {
-	// TODO: maybe support assigning list-like values.
-	l, ok := v.(List)
+	elemser, ok := v.(Elemser)
 	if !ok {
 		throw(ErrCanOnlyAssignList)
 	}
-	paths := make([]string, len(*l.inner))
-	for i, v := range *l.inner {
+	var paths []string
+	for v := range elemser.Elems() {
 		s, ok := v.(String)
 		if !ok {
 			throw(ErrPathMustBeString)
@@ -45,7 +44,7 @@ func (epl *EnvPathList) Set(v Value) {
 		if strings.ContainsAny(path, ":\x00") {
 			throw(ErrPathCannotContainColonZero)
 		}
-		paths[i] = string(s)
+		paths = append(paths, string(s))
 	}
 	epl.set(paths)
 }

eval/list.go

@@ -12,6 +12,13 @@ var (
 	ErrIndexOutOfRange = errors.New("index out of range")
 )
 
+type ListLike struct {
+	Value
+	Lener
+	Elemser
+	IndexOneer
+}
+
 // List is a list of Value's.
 type List struct {
 	inner *[]Value
@@ -38,6 +45,16 @@ func (l List) Len() int {
 	return len(*l.inner)
 }
 
+func (l List) Elems() <-chan Value {
+	ch := make(chan Value)
+	go func() {
+		for _, v := range *l.inner {
+			ch <- v
+		}
+	}()
+	return ch
+}
+
 func (l List) IndexOne(idx Value) Value {
 	i := intIndexWithin(idx, len(*l.inner))
 	return (*l.inner)[i]

eval/value.go

@@ -36,6 +36,19 @@ type Lener interface {
 	Len() int
 }
 
+// Elemser is anything that can produce a series of Value elements.
+type Elemser interface {
+	Elems() <-chan Value
+}
+
+func collectElems(elemser Elemser) []Value {
+	var vs []Value
+	for v := range elemser.Elems() {
+		vs = append(vs, v)
+	}
+	return vs
+}
+
 // Caller is anything may be called on an evalCtx with a list of Value's.
 type Caller interface {
 	Value