CY's challenge: Task 1 in 10 languages; Progress: Day 1 Afternoon

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diff --git a/challenge-147/cheok-yin-fung/README.md b/challenge-147/cheok-yin-fung/README.md
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+This is the beginning of the semester of my PG dip in IT; and I have finished all exams and assignments from the previous semester. Somehow today I want to try to play with programming languages. While Mohammad has said, having fun is important in learning, now I try to do the Task 1 in different programming languages which I am fluent at least at the "sightseeing purpose", within 4 days.
+
+Target list:
+awk bash C++
+Java Node.js Julia
+LISP PHP Perl Smalltalk
+Befunge-93 (if I have that mentality)
+
+Script done (last update: Thursday, January 13, 2022 08:34:23 UTC): 
+1. Julia
+2. Perl
+
+
diff --git a/challenge-147/cheok-yin-fung/julia/ch-1.jl b/challenge-147/cheok-yin-fung/julia/ch-1.jl
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+# The Weekly Challenge 147
+# Task 1 Truncatable Prime
+# Thursday, January 13, 2022 PM03:18:00 
+
+
+left_trun_primes = [2, 3, 5, 7]
+primes = [2, 3, 5, 7]
+index_ltp = [1, 5]
+
+
+
+lastelement(array) = array[length(array)]
+x_no_less_than_sqrt_y(x, y) = x ≤ √y
+
+
+function grep(func, array)
+    ans = []
+    for variable in array
+        if func(variable)
+            push!(ans, variable)
+        end
+    end
+    return Tuple(ans)
+end
+
+
+function is_prime(int)
+    no_less_than_sqrt(x) = x_no_less_than_sqrt_y(x, int)
+    relatively_small_primes = grep(no_less_than_sqrt , primes)
+    for p in relatively_small_primes
+        if int % p == 0
+            return false
+        end
+    end
+    return true
+end
+
+
+function append_arr_of_ltp(digits)
+    k = 0
+    for d = 1:9
+        for ind = index_ltp[digits-1]:(index_ltp[digits]-1)
+            new_num = parse(Int64, string(d) * string(left_trun_primes[ind]))
+            if is_prime(new_num)
+                push!(left_trun_primes, new_num)
+                k += 1
+            end
+        end
+    end
+    push!(index_ltp, lastelement(index_ltp) + k + 1)
+end
+
+
+function append_arr_of_primes(min,max)
+    for num = min:max
+        if is_prime(num)
+            push!(primes, num)
+        end
+    end
+end
+
+
+
+append_arr_of_ltp(2)
+append_arr_of_primes(10,sqrt(999))
+append_arr_of_ltp(3)
+println(left_trun_primes[1:20])
diff --git a/challenge-147/cheok-yin-fung/perl/ch-1.pl b/challenge-147/cheok-yin-fung/perl/ch-1.pl
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+# The Weekly Challenge 147
+# Task 1 Truncatable Prime
+# Thursday, January 13, 2022 PM04:18:51 HKT
+
+use v5.12.0;
+use warnings;
+
+my @ltp = ();
+my @recent_ltp = (2,3,5,7);
+my @new_ltp = ();
+
+my @prime = (2,3,5,7);
+
+sub is_prime {
+    my $t = $_[0];
+    for (my $k = 0; defined($prime[$k]) && $prime[$k] <= sqrt($t) ;$k++) {
+        return 0 if $t % $prime[$k] == 0;
+    } 
+    return 1;
+}
+
+
+
+sub append_arr_of_primes {
+    my $max = $_[0];
+    my @relatively_small_primes = grep { $_ <= sqrt($max) } @prime;
+    HERE: for my $can ($relatively_small_primes[-1]+1..$max) {
+        for my $p (@relatively_small_primes) {
+            next HERE if $can % $p == 0
+        }
+        push @prime, $can;
+    }
+}
+
+
+
+sub append_arr_of_ltp {
+    my $target_size = $_[0];
+    if ($target_size <= (scalar @ltp + scalar @recent_ltp)) {
+        push @ltp, @recent_ltp;
+        return;
+    }
+    for my $d (1..9) {
+        for my $num (@recent_ltp) {
+            my $new_num = $d . $num;
+            push @new_ltp, $new_num if is_prime($new_num);
+        }
+    }
+    push @ltp, @recent_ltp;
+    @recent_ltp = @new_ltp;
+    @new_ltp = ();
+    append_arr_of_ltp($target_size);
+}
+
+
+
+append_arr_of_primes(1000);
+append_arr_of_ltp(20);
+say $_ for @ltp[0..19];
+