apply changes from code review

changes two if statments into a single with an &&, changed const to constexpr,
and changed added strings into os.path.join

Framework/Algorithms/src/CalculatePlaczekSelfScattering.cpp

@@ -115,9 +115,9 @@ void CalculatePlaczekSelfScattering::exec() {
   }
   // set detector law term (eps1)
   std::vector<double> eps1;
-  const double lambdaD = 1.44;
+  constexpr double LAMBDA_D = 1.44;
   for (size_t i = 0; i < xLambda.size() - 1; i++) {
-    double xTerm = -(xLambda[i] + dx) / lambdaD;
+    double xTerm = -(xLambda[i] + dx) / LAMBDA_D;
     eps1.push_back(xTerm * exp(xTerm) / (1.0 - exp(xTerm)));
   }
   /* Placzek
@@ -136,10 +136,8 @@ void CalculatePlaczekSelfScattering::exec() {
   size_t nReserve = 0;
   const API::SpectrumInfo specInfo = inWS->spectrumInfo();
   for (size_t detIndex = 0; detIndex < specInfo.size(); detIndex++) {
-    if (!(specInfo.isMonitor(detIndex))) {
-      if (!(specInfo.l2(detIndex) == 0.0)) {
-        nReserve += 1;
-      }
+    if (!(specInfo.isMonitor(detIndex)) && !(specInfo.l2(detIndex) == 0.0)) {
+      nReserve += 1;
     }
   }
   xLambdas.reserve(nReserve);

scripts/Diffraction/isis_powder/polaris.py

@@ -5,7 +5,7 @@
 #     & Institut Laue - Langevin
 # SPDX - License - Identifier: GPL - 3.0 +
 from __future__ import (absolute_import, division, print_function)
-
+import os
 
 from isis_powder.routines import absorb_corrections, common, instrument_settings
 from isis_powder.abstract_inst import AbstractInst
@@ -55,7 +55,7 @@ class Polaris(AbstractInst):
         # Generate pdf
         run_details = self._get_run_details(self._inst_settings.run_number)
         focus_file_path = self._generate_out_file_paths(run_details)["nxs_filename"]
-        cal_file_name = self._inst_settings.calibration_dir + '/' + self._inst_settings.grouping_file_name
+        cal_file_name = os.path.join(self._inst_settings.calibration_dir, self._inst_settings.grouping_file_name)
         pdf_output = polaris_algs.generate_ts_pdf(run_number=self._inst_settings.run_number,
                                                   focus_file_path=focus_file_path,
                                                   merge_banks=self._inst_settings.merge_banks,