Solution to task 1

1 files changed, 72 insertions, 0 deletions

diff --git a/challenge-133/jo-37/perl/ch-1.pl b/challenge-133/jo-37/perl/ch-1.pl
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+++ b/challenge-133/jo-37/perl/ch-1.pl
@@ -0,0 +1,72 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use integer;
+use Test2::V0;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [N]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N
+    calculate integer square root of N
+
+EOS
+
+
+### Input and Output
+
+say int_sqrt(shift);
+
+
+### Implementation
+
+# Following the formulae in
+# https://en.wikipedia.org/wiki/Integer_square_root#Using_only_integer_division
+
+sub int_sqrt ($n) {
+    my $prev = $n;
+    while () {
+        my $next = ($prev + $n / $prev) / 2;
+        return $prev if $next >= $prev;
+        $prev = $next;
+    }
+}
+
+
+### Examples and tests
+
+use Math::Prime::Util ();
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is int_sqrt(10), 3, 'example 1';
+        is int_sqrt(27), 5, 'example 2';
+        is int_sqrt(85), 9, 'example 3';
+        is int_sqrt(101), 10, 'example 4';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        my $mpu_sqrtint = \&Math::Prime::Util::sqrtint;
+        grep {
+            int_sqrt($_) != $mpu_sqrtint->($_) and !fail "$_ failed";
+        } 1 .. 1e5 or pass 'cross check';
+	}
+
+    done_testing;
+    exit;
+}