eval/vartypes: Add numVar and boolVar.

edit/prompt/prompt.go

@@ -84,9 +84,13 @@ func Rprompt(ed Editor) eval.Callable {
 
 // Implementation for $rprompt-persistent.
 
+// TODO Keep the underlying boolean and float64 values somewhere within the
+// Editor to avoid casts.
+
 // RpromptPersistentVariable returns a variable for $edit:rprompt-persistent.
 func RpromptPersistentVariable() vartypes.Variable {
-	return vartypes.NewValidatedPtrVariable(types.Bool(false), vartypes.ShouldBeBool)
+	b := false
+	return vartypes.NewBool(&b)
 }
 
 // RpromptPersistent extracts $edit:rprompt-persistent.
@@ -96,7 +100,8 @@ func RpromptPersistent(ed Editor) bool {
 
 // MaxWaitVariable returns a variable for $edit:-prompts-max-wait.
 func MaxWaitVariable() vartypes.Variable {
-	return vartypes.NewValidatedPtrVariable(types.String("+Inf"), vartypes.ShouldBeNumber)
+	f := math.Inf(1)
+	return vartypes.NewNumber(&f)
 }
 
 // MaxWait extracts $edit:-prompts-max-wait.

eval/vartypes/bool.go

@@ -0,0 +1,29 @@
+package vartypes
+
+import (
+	"errors"
+
+	"github.com/elves/elvish/eval/types"
+)
+
+var errMustBeBool = errors.New("must be bool")
+
+type boolVar struct {
+	ptr *bool
+}
+
+func NewBool(ptr *bool) Variable {
+	return boolVar{ptr}
+}
+
+func (bv boolVar) Get() types.Value {
+	return types.Bool(*bv.ptr)
+}
+
+func (bv boolVar) Set(v types.Value) error {
+	if b, ok := v.(types.Bool); ok {
+		*bv.ptr = bool(b)
+		return nil
+	}
+	return errMustBeBool
+}

eval/vartypes/number.go

@@ -0,0 +1,32 @@
+package vartypes
+
+import (
+	"errors"
+	"strconv"
+
+	"github.com/elves/elvish/eval/types"
+)
+
+var errMustBeNumber = errors.New("must be number")
+
+type numberVar struct {
+	ptr *float64
+}
+
+func NewNumber(ptr *float64) Variable {
+	return numberVar{ptr}
+}
+
+func (nv numberVar) Get() types.Value {
+	return types.String(strconv.FormatFloat(*nv.ptr, 'E', -1, 64))
+}
+
+func (nv numberVar) Set(v types.Value) error {
+	if s, ok := v.(types.String); ok {
+		if num, err := strconv.ParseFloat(string(s), 64); err == nil {
+			*nv.ptr = num
+			return nil
+		}
+	}
+	return errMustBeNumber
+}

eval/vartypes/string.go

@@ -6,7 +6,7 @@ import (
 	"github.com/elves/elvish/eval/types"
 )
 
-var errMustBeString = errors.New("must be list")
+var errMustBeString = errors.New("must be string")
 
 type stringVar struct {
 	ptr *string