Fix some minor typos in chapter 3.4 (freechipsproject#157)

Author: wunderabt

3.4_functional_programming.ipynb

@@ -58,7 +58,7 @@
    "source": [
     "---\n",
     "# Functional Programming in Scala\n",
-    "Scala functions were introduced in Module 1, and you saw then used a lot in the previous module. Here's a refresher on functions. Functions take any number of inputs and produce one output. Inputs are often called arguments to a function. To produce no output, return the `Unit` type. \n",
+    "Scala functions were introduced in Module 1, and you saw them being used a lot in the previous module. Here's a refresher on functions. Functions take any number of inputs and produce one output. Inputs are often called arguments to a function. To produce no output, return the `Unit` type. \n",
     "\n",
     "<span style=\"color:blue\">**Example: Custom Functions**</span><br>\n",
     "Below are some examples of functions in Scala."
@@ -436,7 +436,7 @@
     "            val expectValue = expected(i-length+1)\n",
     "            //println(s\"expected value is $expectValue\")\n",
     "            c.io.out.expect(expected(i-length+1).U)\n",
-    "            //println(s\"cycle $i, got ${peek(c.io.out)}, expect ${expected(i-length+1)}\")\n",
+    "            //println(s\"cycle $i, got ${c.io.out.peek()}, expect ${expected(i-length+1)}\")\n",
     "        }\n",
     "        c.clock.step(1)\n",
     "    }\n",
@@ -620,4 +620,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 2
-}
+}