is_symlink: prefer native as it's 4x faster

Author: scivision

+stdlib/+native/is_symlink.m

@@ -13,14 +13,19 @@
   backend (1,:) string = ["native", "java", "python", "dotnet", "sys"]
 end
 
-o = stdlib.Backend(mfilename(), backend);
-
-if isscalar(file)
-  ok = o.func(file);
+if backend(1) == "native"
+  try
+    ok = isSymbolicLink(file);
+    b = "native";
+  catch e
+    if e.identifier ~= "MATLAB:UndefinedFunction"
+      rethrow(e)
+    end
+  end
 else
-  ok = arrayfun(o.func, file);
+  o = stdlib.Backend(mfilename(), backend);
+  b = o.backend;
+  ok = o.func(file);
 end
 
-b = o.backend;
-
 end

+stdlib/is_symlink.m

@@ -15,6 +15,6 @@
 
 function result = run_bench(name)
 suite = testsuite(name);
-exp = matlab.perftest.TimeExperiment.limitingSamplingError(MaxSamples=20, RelativeMarginOfError=0.1);
+exp = matlab.perftest.TimeExperiment.limitingSamplingError(MaxSamples=50, RelativeMarginOfError=0.1);
 result = exp.run(suite);
 end

example/BenchmarkIsSymlinkRun.m

@@ -14,7 +14,7 @@
 
 methods (TestParameterDefinition, Static)
 function [is_backend, rs_backend] = setupBackend()
-  is_backend = init_backend('is_symlink');
+  is_backend = cellstr(["native", init_backend('is_symlink')]);
   rs_backend = init_backend('read_symlink');
 end
 end

example/BenchmarkSymlink.m

@@ -51,11 +51,6 @@ function test_is_symlink(tc, p, B_is_symlink)
 tc.verifyEqual(stdlib.is_symlink(p{1}, B_is_symlink), p{2}, p{1})
 end
 
-function test_is_symlink_array(tc, B_is_symlink)
-r = stdlib.is_symlink([tc.link, mfilename() + ".m"], B_is_symlink);
-tc.verifyEqual(r, [true, false], "failed to detect own link")
-end
-
 
 function test_read_symlink_empty(tc, Pre, B_read_symlink)
 tc.verifyEqual(stdlib.read_symlink(Pre, B_read_symlink), "")