Fix var length warning, add Excel example to unit test

Author: Blake-Madden

tests/tetests.cpp

@@ -4269,6 +4269,22 @@ TEST_CASE("PV", "[finance]")
     // Excel: =PV(0.03, 1, 0, 1000)
     CHECK_THAT(WITHIN_TYPE_CAST(tep.evaluate("PV(0.03, 1, 0, 1000)")),
                Catch::Matchers::WithinRel(WITHIN_TYPE_CAST(-970.87), WITHIN_TYPE_CAST(0.0001)));
+
+    // Excel example:
+    // Money paid out of an insurance annuity at the end of every month: $500
+    // Interest rate: 8% annually
+    // Term: 20 years
+    //
+    // Excel formula:
+    // =PV(A3/12, 12*A4, A2, , 0)
+    // =PV(0.08/12, 240, 500, 0, 0)
+    //
+    // Excel result = -59,775.15
+    CHECK_THAT(
+        WITHIN_TYPE_CAST(tep.evaluate("PV(0.08/12, 12*20, 500, 0, 0)")),
+        Catch::Matchers::WithinRel(
+            WITHIN_TYPE_CAST(-59775.15),
+            WITHIN_TYPE_CAST(0.0001)));
     }
 
 TEST_CASE("Nominal", "[finance]")

tinyexpr.cpp

@@ -256,17 +256,17 @@ namespace te_builtins
         }
 
     [[nodiscard]]
-    static te_type te_pv(te_type rate, te_type nper, te_type pmt, te_type fv, te_type type)
+    static te_type te_pv(te_type rate, te_type nper, te_type pmt, te_type futureValue, te_type type)
         {
         if (!std::isfinite(rate) || !std::isfinite(nper) || !std::isfinite(pmt))
             {
             return te_parser::te_nan;
             }
 
         // optional args default like Excel
-        if (!std::isfinite(fv))
+        if (!std::isfinite(futureValue))
             {
-            fv = 0;
+            futureValue = 0;
             }
         if (!std::isfinite(type))
             {
@@ -289,7 +289,7 @@ namespace te_builtins
 
         if (rate == 0.0)
             {
-            return -(fv + pmt * nper);
+            return -(futureValue + pmt * nper);
             }
 
         const te_type powVal = std::pow(1 + rate, nper);
@@ -298,7 +298,7 @@ namespace te_builtins
             return te_parser::te_nan;
             }
 
-        return -(fv + pmt * (1 + rate * type) * (powVal - 1) / rate) / powVal;
+        return -(futureValue + pmt * (1 + rate * type) * (powVal - 1) / rate) / powVal;
         }
 
     [[nodiscard]]