support for __result__ in web components and SqLambda

packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx

@@ -248,7 +248,7 @@ export const ExpressionViewer: React.FC<Props> = ({ value, width }) => {
           {(_) =>
             value.value
               .entries()
-              .filter(([key, _]) => !key.match(/^(Math|System)\./))
+              .filter(([key, _]) => !key.match(/^(__result__)$/))
               .map(([key, r]) => (
                 <ExpressionViewer
                   key={key}

packages/squiggle-lang/src/js/SqLambda.ts

@@ -18,23 +18,28 @@ export class SqLambda {
     // Might be good to use uuid instead, but there's no way to remove sources from projects.
     // So this is not thread-safe.
     const callId = "__lambda__";
-    if (this.location.path.root !== "bindings") {
-      return {
-        tag: "Error",
-        value: SqError.createTodoError("Only bindings lambdas can be rendered"),
-      };
-    }
     const quote = (arg: string) =>
       `"${arg.replace(new RegExp('"', "g"), '\\"')}"`;
     const argsSource = args
       .map((arg) => (typeof arg === "number" ? arg : quote(arg)))
       .join(",");
-    const functionNameSource = this.location.path.items
+
+    // end expression values are exposed in bindings via secret `__result__` variable and we can access them through it
+    const pathItems = [
+      ...(this.location.path.root === "result" ? ["__result__"] : []),
+      ...this.location.path.items,
+    ];
+
+    // full function name, e.g. foo.bar[3].baz
+    const functionNameSource = pathItems
       .map((item, i) =>
         typeof item === "string" ? (i ? "." + item : item) : `[${item}]`
       )
       .join("");
+
+    // something like: foo.bar[3].baz(1,2,3)
     const source = `${functionNameSource}(${argsSource})`;
+
     project.setSource(callId, source);
     project.setContinues(callId, [sourceId]);
     project.run(callId);