From 84b66adda38622f463709dfd0cefbe670588578d Mon Sep 17 00:00:00 2001
From: Nathan Wallach <tani@technion.ac.il>
Date: Thu, 26 May 2022 16:50:59 +0300
Subject: [PATCH 1/2] Limit loop to compute factorial to n<=170, for n>170
 return Perl Inf, as that would be the result of the calculation used for any
 such n due to overflow of the Perl floating point data type.

---
 lib/Parser/UOP/factorial.pm | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/Parser/UOP/factorial.pm b/lib/Parser/UOP/factorial.pm
index 65600fec45..83b8866f28 100644
--- a/lib/Parser/UOP/factorial.pm
+++ b/lib/Parser/UOP/factorial.pm
@@ -25,6 +25,7 @@ sub _eval {
   my $n = shift; my $f = 1;
   $self->Error("Factorial can only be taken of (non-negative) integers")
     unless $n =~ m/^\d+$/;
+  return Inf if $n > 170;
   while ($n > 0) {$f *= $n; $n--}
   return $f;
 }

From a25ced5ca3ab300e372d99b2b9c5d774f4866fbd Mon Sep 17 00:00:00 2001
From: Peter Staab <peter.staab@gmail.com>
Date: Fri, 27 May 2022 07:20:28 -0400
Subject: [PATCH 2/2] Factorial unit test (#1)

* Added a test for the factorial.

* FIX: clarified some of the language in the tests.
---
 lib/PGEnvironment.pm        |  3 +-
 lib/Parser/UOP/factorial.pm |  2 +-
 t/math_objects/factorial.t  | 78 +++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 t/math_objects/factorial.t

diff --git a/lib/PGEnvironment.pm b/lib/PGEnvironment.pm
index c7bd9b793e..51c382c13e 100644
--- a/lib/PGEnvironment.pm
+++ b/lib/PGEnvironment.pm
@@ -62,7 +62,8 @@ sub new {
 		# Load from the conf file.
 		$self->{pg_dir} = $ENV{PG_ROOT};
 
-		my $defaults_file = $self->{pg_dir} . "/conf/pg_defaults.yml";
+		my $defaults_file = "$self->{pg_dir}/conf/pg_defaults.yml";
+		$defaults_file = "$self->{pg_dir}/conf/pg_defaults.dist.yml" unless -r $defaults_file;
 		die "Cannot read the configuration file $defaults_file" unless -r $defaults_file;
 
 		my $options = LoadFile($defaults_file);
diff --git a/lib/Parser/UOP/factorial.pm b/lib/Parser/UOP/factorial.pm
index 83b8866f28..a5f8add846 100644
--- a/lib/Parser/UOP/factorial.pm
+++ b/lib/Parser/UOP/factorial.pm
@@ -25,7 +25,7 @@ sub _eval {
   my $n = shift; my $f = 1;
   $self->Error("Factorial can only be taken of (non-negative) integers")
     unless $n =~ m/^\d+$/;
-  return Inf if $n > 170;
+  return $self->Package("Infinity")->new() if $n > 170;
   while ($n > 0) {$f *= $n; $n--}
   return $f;
 }
diff --git a/t/math_objects/factorial.t b/t/math_objects/factorial.t
new file mode 100644
index 0000000000..5342054ad5
--- /dev/null
+++ b/t/math_objects/factorial.t
@@ -0,0 +1,78 @@
+use warnings;
+use strict;
+
+package main;
+
+use Test::More;
+use Test::Exception;
+
+# The following needs to include at the top of any testing down to END OF TOP_MATERIAL.
+
+BEGIN {
+	die 'PG_ROOT not found in environment.\n' unless $ENV{PG_ROOT};
+	$main::pg_dir = $ENV{PG_ROOT};
+}
+
+use lib "$main::pg_dir/lib";
+
+require("$main::pg_dir/t/build_PG_envir.pl");
+
+## END OF TOP_MATERIAL
+
+use Parser;
+
+loadMacros('MathObjects.pl');
+
+Context('Numeric');
+Context()->variables->add(y => "Real");
+Context()->variables->add(n => "Real");
+
+my $five_fact = Compute('5!');
+
+use Data::Dumper;
+print Dumper $five_fact->class;
+
+is($five_fact->class, 'Real',   'factorial: check class of object');
+is($five_fact->type,  'Number', 'factorial: check type of object');
+
+ok(Value::isValue($five_fact),    'factorial: check if an object is a value');
+ok(Value::isNumber($five_fact),   'factorial: check if an object is a number');
+ok(Value::isReal($five_fact),     'factorial: check if a number is a real number');
+ok(!Value::isComplex($five_fact), 'factorial: check if an integer is complex');
+ok(!Value::isFormula($five_fact), 'factorial: check if a number is not a formula');
+
+is($five_fact->value,120, 'factorial: 5! is 120');
+is(Compute("0!")->value, 1, 'factorial: 0! is 1');
+
+note('The double factorial is not defined here.');
+my $four_double_fact = Compute("4!!")->value;
+ok(6.2e+23 < $four_double_fact && $four_double_fact < 6.3e+23, 'factorial: 4!! is defined as (4!)!=24!' );
+
+ok(Compute("170!") > 1e+306, 'factorial: 170! is large but not infinite.');
+
+note('Tests for throwing exceptions.');
+
+throws_ok {
+	Compute("(-1)!");
+}
+qr/Factorial can only be taken of \(non-negative\) integers/, 'factorial: can\'t take factorial of negative integers.';
+
+throws_ok {
+	Compute("1.5!");
+}
+qr/Factorial can only be taken of \(non-negative\) integers/, 'factorial: can\'t take factorial of non-integer reals.';
+
+note('Try taking factorials of variables');
+my $n_fact = Compute("n!");
+is($n_fact->class, "Formula", "factorial: n! is a Formula");
+is($n_fact->type,  "Number",  "factorial: n! has type is Number");
+is($n_fact->eval(n=>5), 120, 'factorial: n! evaluated at n=5 is correct.');
+
+# check infinite values
+note('Tests for infinite values');
+
+my $large_fact = Compute('171!');
+my $inf = Compute('inf');
+is($large_fact->value, $inf, '171! is infinite.');
+
+done_testing();