Add array.each()

Author: jamiehale

examples/tests/arrays.tab

@@ -96,6 +96,27 @@ assert(not a.includes(100))
 assert(not a.includes('abc'))
 ############################################################################
 
+############################################################################
+# Array.each
+#
+# The each function applies a function to each member of the array. It's
+# one of the Tablescript ways of "looping".
+a = [1, 2, 3, 4, 5]
+state = {
+  value: 0
+}
+f = fn(state) { fn(n) { state.value = n } }
+assert(a.each(f(state)) == 5)
+assert(state.value == 5)
+
+# The each function can also take a 2nd parameter that is the 0-based index
+# of the array member passed as the 1st parameter
+b = [0, 0, 0, 0, 0]
+f = fn(state) { fn(n, i) { state[i] = n + 1 } }
+assert(a.each(f(b)) == 6)
+assert(b == [2, 3, 4, 5, 6])
+############################################################################
+
 ############################################################################
 # Array.map
 #

src/values/array.js

@@ -82,6 +82,15 @@ const multiplyBy = entries => (context, other) => createArrayValue(
   ).reduce((all,n) => ([...all, ...entries]), [])
 );
 
+const each = entries => createNativeFunctionValue(['f'], async context => {
+  const f = requiredParameter(context, 'f');
+  let result = context.factory.createUndefined();
+  for (let i = 0; i < entries.length; i++) {
+    result = await f.callFunction(context, [entries[i], context.factory.createNumericValue(i)]);
+  }
+  return result;
+});
+
 const reduce = entries => createNativeFunctionValue(['reducer', 'initialValue'], async context => {
   const reducer = requiredParameter(context, 'reducer');
   const initialValue = requiredParameter(context, 'initialValue');
@@ -218,6 +227,7 @@ export const createArrayValue = entries => createValue(
   identicalTo(entries),
   nativeEquals(entries),
   {
+    each: each(entries),
     reduce: reduce(entries),
     map: map(entries),
     filter: filter(entries),