updates based on feedback

Author: samukweku

docs/api/math/isna.rst

@@ -13,7 +13,9 @@
         Input columns.
 
     return: FExpr
-        f-expression that returns `0` for valid elements and `1` otherwise. All the resulting columns will have `bool8` stypes and as many rows/columns as there are in `cols`.
+        f-expression that returns `0` for valid elements and `1` otherwise. 
+        All the resulting columns will have `bool8` stypes 
+        and as many rows/columns as there are in `cols`.
 
     Examples
     --------

src/core/expr/fbinary/fexpr__eq__.cc

@@ -67,12 +67,9 @@ Column FExpr__eq__::evaluate1(Column&& lcol, Column&& rcol) const {
     if (type1.is_void()) {
       std::swap(lcol, rcol);
     }
-    switch (type0.stype()) {
-      case SType::VOID:    
-        return Const_ColumnImpl::make_bool_column(lcol.nrows(), true);      
-      default:
-        return Column(new Isna_ColumnImpl(std::move(lcol)));
-    }
+    if (type0.stype() == SType::VOID) {
+      return Const_ColumnImpl::make_bool_column(lcol.nrows(), true);
+    } else return Column(new Isna_ColumnImpl(std::move(lcol)));
   } else {
     switch (type0.stype()) {
       case SType::BOOL:
@@ -93,9 +90,6 @@ Column FExpr__eq__::evaluate1(Column&& lcol, Column&& rcol) const {
       "types `" << type1 << "` and `" << type2 << "`";
 }
 
+}}  // namespace dt::expr
 
 
-
-
-
-}}  // namespace dt::expr

tests/test-f.py

@@ -502,4 +502,5 @@ def test_codes():
 def test_isna():
     assert str(dt.math.isna(f.A)) == str(f.A.math_isna())
     DT = dt.Frame(A = [None, 9, 8, 2, 3, None, None, 3, 0, 5, 5, 8, None])
-    assert_equals (DT[:, dt.math.isna(f.A)], DT[:, f.A.math_isna()])
+    assert_equals (DT[:, dt.math.isna(f.A)], DT[:, f.A.math_isna()])
+