fixes source-academy#837 (source-academy#1026)

Author: martin-henz

xml/chapter3/section3/subsection5.xml

@@ -1561,6 +1561,53 @@ const answer = v_prod(v_sum("a", "b"), v_sum("c", "d"));
     expression-oriented style in terms of the imperative implementation,
     it is very difficult to do the converse.</FOOTNOTE>
     <LABEL NAME="ex:3_37"/>
+    <SOLUTION>
+      <SNIPPET>
+	<REQUIRES>make_connector</REQUIRES>
+	<REQUIRES>has_value</REQUIRES>
+	<REQUIRES>for_each_except</REQUIRES>
+	<REQUIRES>inform_about_value</REQUIRES>
+	<REQUIRES>multiplier_2</REQUIRES>
+	<REQUIRES>adder</REQUIRES>
+	<REQUIRES>constant</REQUIRES>
+	<JAVASCRIPT>
+// Solution provided by GitHub user clean99
+
+function cminus(x, y) {
+    const z = make_connector();
+    const u = make_connector();
+    const v = make_connector();
+    constant(-1, u);
+    multiplier(u, y, v);
+    adder(x, v, z);
+    return z;
+}
+
+function cmul(x, y) {
+    const z = make_connector();
+    multiplier(x, y, z);
+    return z;
+}
+
+function cdiv(x, y) {
+    const z = make_connector();
+    const u = make_connector();
+    const v = make_connector();
+    constant(1, v);
+    // y * u = 1 -> u = 1 / y
+    multiplier(y, u, v);
+    multiplier(x, u, z);
+    return z;
+}
+
+function cv(val) {
+    const x = make_connector();
+    constant(val, x);
+    return x;
+}
+	</JAVASCRIPT>
+      </SNIPPET>
+    </SOLUTION>
   </EXERCISE>
 
   <INDEX>propagation of constraints<CLOSE/></INDEX>