delay/Lazy fix #2

js/src/core/concatenate/app3.js → js/src/0-core/concatenate/app3.js

@@ -1,5 +1,8 @@
 const app3 = function ( A , list , B ) {
 
+	A = A.force( ) ;
+	B = B.force( ) ;
+
 	if ( A instanceof Empty ) return extendleft( B , list ) ;
 	if ( B instanceof Empty ) return extend( A , list ) ;
 
@@ -9,11 +12,11 @@ const app3 = function ( A , list , B ) {
 	return new Deep(
 		A.measure ,
 		A.left ,
-		app3(
+		delay( ( ) => app3(
 			A.middle ,
 			nodes( A.measure , [ ...chain( A.right , list , B.left ) ] ) ,
 			B.middle
-		) ,
+		) ) ,
 		B.right
 	) ;
 

js/src/core/split/deepL.js → js/src/0-core/split/deepL.js

@@ -9,7 +9,7 @@ function deepL ( M , left , middle , right ) {
 
 		if ( middle.empty( ) ) return from_iterable( M , right ) ;
 
-		return new Deep( M , middle.head( ).digit( ) , middle.tail( ) , right ) ;
+		return new Deep( M , middle.head( ).digit( ) , delay( ( ) => middle.tail( ) ) , right ) ;
 	}
 
 	return new Deep( M , digit( left ) , middle , right ) ;

js/src/core/split/deepR.js → js/src/0-core/split/deepR.js

@@ -9,7 +9,7 @@ function deepR ( M , left , middle , right ) {
 
 		if ( middle.empty( ) ) return from_iterable( M , left ) ;
 
-		return new Deep( M , left , middle.init( ) , middle.last( ).digit( ) ) ;
+		return new Deep( M , left , delay( ( ) => middle.init( ) ) , middle.last( ).digit( ) ) ;
 	}
 
 	return new Deep( M , left , middle , digit( right ) ) ;

js/src/tree/0-sugar/Tree.js → js/src/3-tree/0-sugar/Tree.js

@@ -1,6 +1,10 @@
 
 class Tree {
 
+	force ( ) {
+		return this ;
+	}
+
 	takeUntil ( p ) {
 		return this.split( p )[0] ;
 	}

js/src/tree/1-base/2-Deep.js → js/src/3-tree/1-base/2-Deep.js

@@ -32,7 +32,7 @@ class Deep extends Tree {
 				return from_iterable( this.measure , this.right ) ;
 			}
 
-			return new Deep( this.measure , this.middle.head( ).digit( ) , this.middle.tail( ) , this.right ) ;
+			return new Deep( this.measure , this.middle.head( ).digit( ) , delay( ( ) => this.middle.tail( ) ) , this.right ) ;
 
 		}
 
@@ -48,7 +48,7 @@ class Deep extends Tree {
 				return from_iterable( this.measure , this.left ) ;
 			}
 
-			return new Deep( this.measure , this.left , this.middle.init( ) , this.middle.last( ).digit( ) ) ;
+			return new Deep( this.measure , this.left , delay( ( ) => this.middle.init( ) ) , this.middle.last( ).digit( ) ) ;
 
 		}
 

js/src/4-lazy/Lazy.js

@@ -0,0 +1,62 @@
+class Lazy extends Tree {
+
+	constructor ( thunk ) {
+		super( ) ;
+		this.tree = null ;
+		this.thunk = thunk ;
+	}
+
+	force ( ) {
+		if ( this.tree === null ) this.tree = this.thunk( ) ;
+		return this.tree ;
+	}
+
+	empty ( ) {
+		return this.force( ).empty( ) ;
+	}
+
+	get v ( ) {
+		return this.force( ).v ;
+	}
+
+	head ( ) {
+		return this.force( ).head( ) ;
+	}
+
+	last ( ) {
+		return this.force( ).last( ) ;
+	}
+
+	unshift ( value ) {
+		return this.force( ).unshift( value ) ;
+	}
+
+	push ( value ) {
+		return this.force( ).push( value ) ;
+	}
+
+	tail ( ) {
+		return this.force( ).tail( ) ;
+	}
+
+	init ( ) {
+		return this.force( ).init( ) ;
+	}
+
+	splitTree ( p , i ) {
+		return this.force( ).splitTree( p , i ) ;
+	}
+
+	split ( p ) {
+		return this.force( ).split( p ) ;
+	}
+
+	concat ( other ) {
+		return this.force( ).concat( other ) ;
+	}
+
+	* [Symbol.iterator] ( ) {
+		yield* this.force( ) ;
+	}
+
+}

js/src/4-lazy/delay.js

@@ -0,0 +1,3 @@
+function delay ( thunk ) {
+	return new Lazy( thunk ) ;
+}