Switch the renderer over to using the new is_truthy value and add the injection of $idx and $len into the context tree.

src/renderer/iteration_context.rs

@@ -6,6 +6,7 @@ use crate::renderer::Renderable;
 use crate::renderer::Truthiness;
 use crate::renderer::WalkError;
 use crate::{parser::Filter, parser::OwnedLiteral, renderer::Walkable};
+use std::convert::TryInto;
 
 use std::cmp::Ordering;
 
@@ -21,10 +22,11 @@ pub struct IterationContext {
 }
 
 impl IterationContext {
-    pub fn new(idx: u64, len: u64) -> Self {
+    pub fn new(idx: usize, len: usize) -> Self {
+        // TODO: it would be nice to handle usize vs u64 better
         IterationContext {
-            idx: OwnedLiteral::LPositiveInteger(idx),
-            len: OwnedLiteral::LPositiveInteger(len),
+            idx: OwnedLiteral::LPositiveInteger(idx.try_into().unwrap()),
+            len: OwnedLiteral::LPositiveInteger(len.try_into().unwrap()),
         }
     }
 }