🦋11. Compiler stages and targets in Perl 6

Welcome to the new year! Today, let us switch for a while from the discussion about obsolete messages to something different. Stages If you followed the exercises in the previous posts, you might have noticed that some statistics was printed in the console when compiling Rakudo: Stage start : 0.000 Stage parse : 44.914 Stage syntaxcheck: … Continue reading “🦋11. Compiler stages and targets in Perl 6”

🔬10. Obsolete syntax error messages, part 2

Today, we continue exploring the error messages that Rakudo developers embedded to detect old Perl 5 constructions in the Perl 6 code. The obs method But first, let’s make a small experiment and add a call to the obs method in the rule parsing the for keyword. rule statement_control:sym<for> { <sym><.kok> {} [ <?before ‘my’? … Continue reading “🔬10. Obsolete syntax error messages, part 2”

🔬9. Obsolete syntax error messages in Perl 6, part 1

Yesterday, we saw an error message about the improper syntax of the ternary operator. Let’s look at other similar things that the Rakudo designers has implemented for us to make the transition from Perl 5 smoother. First of all, the Perl 6 grammar file (src/Perl6/Grammar.nqp) contains four different methods for reacting to obsolete syntax: method … Continue reading “🔬9. Obsolete syntax error messages in Perl 6, part 1”

🔬8. Digging into operator precedence in Perl 6, part 2

Yesterday, we took a look at how the ? and so operators are dispatched depending on the type of the variable. We did it with the intention to understand what is the difference between them. Here is once again an excerpt from the src/core/Bool.pm file, where the bodies of the subs look alike: proto sub … Continue reading “🔬8. Digging into operator precedence in Perl 6, part 2”

🔬7. Digging into operator precedence in Perl 6, part 1

Today, we’ll once again look at the src/core/Bool.pm file. This is a good example of a full-fledged Perl 6 class, which is still not very difficult to examine. Look at the definitions of the ? and so operators: proto sub prefix:<?>(Mu $) is pure {*} multi sub prefix:<?>(Bool:D \a) { a } multi sub prefix:<?>(Bool:U … Continue reading “🔬7. Digging into operator precedence in Perl 6, part 1”

🔬6. The dd routine of Rakudo Perl 6

In Rakudo, there is a useful routine dd, which is not a part of Perl 6 itself. It dumps its argument(s) in a way that you immediately see the type and content of a variable. For example: $ ./perl6 -e’my Bool $b = True; dd($b)’ Bool $b = Bool::True It works well with data of … Continue reading “🔬6. The dd routine of Rakudo Perl 6”

🔬5. Lurking behind interpolation in Perl 6

In the previous articles, we’ve seen that the undefined value cannot be easily interpolated in a string, as an exception occurs. Today, our goal is to see where exactly that happens in the source code of Rakudo. So, as soon as we’ve looked at the Boolean values, let’s continue with them. Open perl6 in the … Continue reading “🔬5. Lurking behind interpolation in Perl 6”

🔬4. Exploring the Bool type in Perl 6, part 2

Today, we are continuing reading the source codes of the Bool class: src/core/Bool.pm, and will look at the methods that calculate the next or the previous values, or increment and decrement the values. For the Boolean type, it sounds simple, but you still have to determine the behaviour of the edge cases. pred and succ … Continue reading “🔬4. Exploring the Bool type in Perl 6, part 2”

🔬3. Playing with the code of Rakudo Perl 6

Yesterday, we looked at the two methods of the Bool class that return strings. The string representation that the functions produce is hardcoded in the source code. Let’s use this observation and try changing the texts. So, here is the fragment that we will modify: Bool.^add_multi_method(‘gist’, my multi method gist(Bool:D:) { self ?? ‘True’ !! … Continue reading “🔬3. Playing with the code of Rakudo Perl 6”