Merge bindings function

Value: [0.0001 to 0.005]

packages/components/src/index.ts

@@ -9,3 +9,5 @@ import SquigglePlayground, {
   renderSquigglePlaygroundToDom,
 } from "./components/SquigglePlayground";
 export { SquigglePlayground, renderSquigglePlaygroundToDom };
+
+export { mergeBindings } from "@quri/squiggle-lang";

packages/squiggle-lang/__tests__/TS/JS_test.ts

@@ -1,4 +1,9 @@
-import { Distribution, resultMap, defaultBindings } from "../../src/js/index";
+import {
+  Distribution,
+  resultMap,
+  defaultBindings,
+  mergeBindings,
+} from "../../src/js/index";
 import { testRun, testRunPartial } from "./TestHelpers";
 
 function Ok<b>(x: b) {
@@ -66,6 +71,17 @@ describe("Partials", () => {
       value: 10,
     });
   });
+  test("Can merge bindings from three partials", () => {
+    let bindings1 = testRunPartial(`x = 1`);
+    let bindings2 = testRunPartial(`y = 2`);
+    let bindings3 = testRunPartial(`z = 3`);
+    expect(
+      testRun(`x + y + z`, mergeBindings([bindings1, bindings2, bindings3]))
+    ).toEqual({
+      tag: "number",
+      value: 6,
+    });
+  });
 });
 
 describe("JS Imports", () => {

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

@@ -48,7 +48,7 @@ export function run(
   let i = imports ? imports : defaultImports;
   let e = environment ? environment : defaultEnvironment;
   let res: result<expressionValue, errorValue> = evaluateUsingOptions(
-    { externalBindings: mergeImports(b, i), environment: e },
+    { externalBindings: mergeImportsWithBindings(b, i), environment: e },
     squiggleString
   );
   return resultMap(res, (x) => createTsExport(x, e));
@@ -67,12 +67,12 @@ export function runPartial(
 
   return evaluatePartialUsingExternalBindings(
     squiggleString,
-    mergeImports(b, i),
+    mergeImportsWithBindings(b, i),
     e
   );
 }
 
-function mergeImports(
+function mergeImportsWithBindings(
   bindings: externalBindings,
   imports: jsImports
 ): externalBindings {
@@ -90,6 +90,12 @@ type jsImports = { [key: string]: jsValue };
 export let defaultImports: jsImports = {};
 export let defaultBindings: externalBindings = {};
 
+export function mergeBindings(
+  allBindings: externalBindings[]
+): externalBindings {
+  return allBindings.reduce((acc, x) => ({ ...acc, ...x }));
+}
+
 function createTsExport(
   x: expressionValue,
   environment: environment