Merge branch 'master' into dependabot/npm_and_yarn/xpath-0.0.34

package.json

@@ -25,13 +25,13 @@
   },
   "homepage": "https://sourceacademy.org/sicpjs",
   "devDependencies": {
-    "@babel/node": "^7.22.19",
-    "@babel/core": "^7.23.5",
-    "@babel/preset-env": "^7.23.5",
+    "@babel/node": "^7.24.6",
+    "@babel/core": "^7.24.6",
+    "@babel/preset-env": "^7.24.6",
     "fs-extra": "^11.2.0",
     "http-server": "^14.1.1",
     "husky": "^8.0.3",
-    "js-slang": "^1.0.37",
+    "js-slang": "^1.0.57",
     "lz-string": "^1.5.0",
     "prettier": "^2.8.8",
     "xmldom": "^0.6.0",

xml/chapter2/section1/subsection4.xml

@@ -411,7 +411,7 @@ function the_trouble_maker(xl, xu, yl, yu) {
     const p2 = xl * yu;
     const p3 = xu * yl;
     const p4 = xu * yu;
-    make_interval(math_min(p1, p2, p3, p4),
+    return make_interval(math_min(p1, p2, p3, p4),
                   math_max(p1, p2, p3, p4));
 }
 function mul_interval(x, y) {  

xml/chapter2/section3/subsection2.xml

@@ -1340,7 +1340,7 @@ list("x", "+", list(3, "*", list("x", "+", list("y", "+", 2))))
 	    example:
 	    <SNIPPET EVAL="no">
 	      <JAVASCRIPT>
-list("x", "+", "3", "*", list("x", "+", "y", "+", 2))
+list("x", "+", 3, "*", list("x", "+", "y", "+", 2))
               </JAVASCRIPT>
 	    </SNIPPET>
 	  </JAVASCRIPT>
@@ -1436,15 +1436,27 @@ deriv(list("x", "*", 4), "x");
 	    <EXAMPLE>example_2.61_2</EXAMPLE>
 	    <JAVASCRIPT>
 function items_before_first(op, s) {
-    return head(s) === op
+    return is_string(head(s)) &amp;&amp; head(s) === op
            ? null
            : pair(head(s),
                   items_before_first(op, tail(s)));
 }
 function items_after_first(op, s) {
-    return head(s) === op
+    return is_string(head(s)) &amp;&amp; head(s) === op
            ? tail(s)
-           : items_after_first(op, tail(s);
+           : items_after_first(op, tail(s));
+}
+function simplify_unary_list(s) {
+    return is_pair(s) &amp;&amp; is_null(tail(s))
+           ? head(s)
+           : s;
+}
+function contains_plus(s) {
+    return is_null(s)
+           ? false
+           : is_string(head(s)) &amp;&amp; head(s) === "+"
+             ? true
+             : contains_plus(tail(s));
 }
 function make_sum(a1, a2) {
     return number_equal(a1, 0)
@@ -1458,14 +1470,13 @@ function make_sum(a1, a2) {
 // a sequence of terms and operators is a sum
 // if and only if at least one + operator occurs
 function is_sum(x) {
-    return is_pair(x) &amp;&amp;
-           ! (is_null(member("+", x));
+    return is_pair(x) &amp;&amp; contains_plus(x);
 }
 function addend(s) {
-    return items_before_first("+", s);
+    return simplify_unary_list(items_before_first("+", s));
 }
 function augend(s) {
-    return items_after_first("+", s);
+    return simplify_unary_list(items_after_first("+", s));
 }
 function make_product(m1, m2) {
     return number_equal(m1, 0) || number_equal(m2, 0)
@@ -1481,13 +1492,13 @@ function make_product(m1, m2) {
 // a sequence of terms and operators is a product
 // if and only if no + operator occurs
 function is_product(x) {
-    return is_pair(x) &amp;&amp; is_null(member("+", x);
+    return is_pair(x) &amp;&amp; ! contains_plus(x);
 }
 function multiplier(s) {
-    return items_before_first("*", s);
+    return simplify_unary_list(items_before_first("*", s));
 }
 function multiplicand(s) {
-    return items_after_first("*", s);
+    return simplify_unary_list(items_after_first("*", s));
 }
 function deriv(exp, variable) {
     return is_number(exp)