Function signature fix for repeating arguments (#760)

* fix(signature): Enable the use of repeating parameters in lambda functions

Before this change, a function signature containing a repeating symbol (eg. <n+>) would copy the first of those arguments into every matching parameter (eg. `function($a1, $a2)<n+>{[$a1, $a2]}(1, 2)` returns [1, 1] instead of [1, 2]) instead of copying each argument to each parameter respectively.

* test(signature): Add tests for variadic lambda functions

"Variadic" just means a function can take an arbitrary number of arguments (eg. <n+>).

One important note here is that this implementation doesn't actually support an arbitrary number of arguments, only as many as the number of parameters you're willing to add to your function. I tried to change as little as possible while still squashing the bug.

I would recommend a breaking change that would bind each repeating parameter to an array of its provided arguments. Then, you could write something like this: `function($nums, $str)<n+s>{{$str: $count($nums)}}`

Author: Turings98apprentice

case035.json

@@ -0,0 +1,9 @@
+{
+    "expr": "λ($arg1, $arg2)<n+n:o>{{\"$arg1\": $arg1, \"$arg2\": $arg2}}(1, 2, 3)",
+    "dataset": null,
+    "bindings": {},
+    "result": {
+        "$arg1": 1,
+        "$arg2": 2
+    }
+}

case036.json

@@ -0,0 +1,6 @@
+{
+    "expr": "λ($arg1, $arg2, $arg3)<n+s:a<n>>{[$arg1, $arg2, $arg3]}(1, 2, \"a\")",
+    "dataset": null,
+    "bindings": {},
+    "result": [1, 2, "a"]
+}

case037.json

@@ -0,0 +1,6 @@
+{
+    "expr": "λ($arg1, $arg2, $arg3)<n+s-:a<n>>{[$arg1, $arg2, $arg3]}(1, 2, \"a\")",
+    "data": "b",
+    "bindings": {},
+    "result": [1, 2, "a"]
+}

case038.json

@@ -0,0 +1,6 @@
+{
+    "expr": "λ($arg1, $arg2, $arg3)<n+s-:a<n>>{[$arg1, $arg2, $arg3]}(1, 2)",
+    "data": "b",
+    "bindings": {},
+    "result": [1, 2, "b"]
+}

case039.json

@@ -0,0 +1,9 @@
+{
+    "expr": "λ($arg1, $arg2)<a<n>+:o>{{'$arg1': $arg1, '$arg2': $arg2}}([1, 2], [3, 4], [5, 6])",
+    "data": "b",
+    "bindings": {},
+    "result": {
+        "$arg1": [1, 2],
+        "$arg2": [3, 4]
+    }
+}

case040.json

@@ -0,0 +1,6 @@
+{
+    "expr": "λ($arg1, $arg2)<s?n+:a<n>>{[$arg1, $arg2]}(1, 2, 3)",
+    "dataset": null,
+    "bindings": {},
+    "result": [1, 2]
+}

src/signature.js

@@ -252,15 +252,15 @@ const signature = (() => {
                                 argIndex++;
                             }
                         } else {
-                            // may have matched multiple args (if the regex ends with a '+'
+                            // may have matched multiple args (if the regex ends with a '+')
                             // split into single tokens
                             match.split('').forEach(function (single) {
+                                arg = args[argIndex];
                                 if (param.type === 'a') {
                                     if (single === 'm') {
                                         // missing (undefined)
                                         arg = undefined;
                                     } else {
-                                        arg = args[argIndex];
                                         var arrayOK = true;
                                         // is there type information on the contents of the array?
                                         if (typeof param.subtype !== 'undefined') {