Errata for Learning Perl 6

the package name is not rakudo-star should have been C:\ choco install rakudostar instead.

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There are two code sections that look like this: put 'Hello Perl 6!'; put 'The time is ', now; In the second one, remove the final semicolon: put 'Hello Perl 6!'; put 'The time is ', now

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On p8 the bottom example: loop { state $count = 0; sleep 1; print $count, "\r"; } is it perhaps missing a ++? as in: loop { state $count = 0; sleep 1; print $count++, "\r"; } It just seems a little pointless without the ++.

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p6doc language/variables gives No such type 'language/variables' but p6doc variables seems to give the desired documentation page

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The env command is usually available under /usr/bin/env. Only some systems provide /bin/env in addition to /usr/bin/env.

Note from the Author or Editor:
substitute /usr/bin/env for /bin/env as noted

The phrase "For numbers, 0 is False and everything else is True" appears at the end of the second paragraph, and is repeated at the end of the third. This phrase should only appear once.

Note from the Author or Editor:
Remove the sentence from the second paragraph.

The variable $n needs to be declared with "my". % perl6 > $n = 10 10 > 7 < $n < 15 ought to be changed to % perl6 > my $n = 10 10 > 7 < $n < 15

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Change as noted.

In the snippet my Int $number; put $number2.^name; # Int the first and the second variable names are different. They should be the same.

Note from the Author or Editor:
change the second variable name to match the first ($number)

put .numerator, '/', .denominator, ' = ' given $sum; is missing the final printout of $sum maybe should be something like: put .numerator, '/', .denominator, ' = ', $sum given $sum;

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The book says: > Q :q 「This quote \「\」 escapes」 This quote 「 escapes But it should be: > Q :q 「This quote \「\」 escapes」 This quote 「」 escapes

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put 'hamadryas PERLICUS'.tc; should be put 'hamadryas PERLICUS'.tclc;

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Change as noted.

Result is True, not False ( 'Hama...'.fc.starts-with: 'hama' )

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In second code example from bottom, change to: > 'Hamadryas perlicus'.fc.starts-with: 'hama' True

using the code if $answer { 'You chose <', $answer, '>' } has an interesting side effect. It looks like put do { 'You chose <', $answer, '>' } puts a single space between the arguments: > $answer = ' X '.trim; X > put do { 'You chose <', $answer, '>' } You chose < X > > put 'You chose <', $answer, '>' You chose <X> This makes it look (erroneously) like .trim compresses leading and trailing spaces down to single spaces, not removing them entirely, and yielding the following output when the script is modified to use .trim: % perl6 prompt.p6 What's your favorite animal? Butterfly You chose < Butterfly > An easy way to fix this would be to concatenate them using ~, thus changing the 3rd line of the script to if $answer { 'You chose <' ~ $answer ~ '>' } This way, when the program is changed to use .trim, you get the following result: % perl6 prompt.p6 What's your favorite animal? Butterfly You chose <Butterfly>

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Changed as noted

The warning "You cannot make an empty List with $(): that's just Nil" only applies to version 6.c of the Raku programming language. From Rakudo 2018.10 on $() hasn't got any special meaning and makes an empty list (unless "use v6.c" is effective).

Note from the Author or Editor:
Remove the warning box on page 90.

The second code sample reads my $countdown = <1 2 3 4 5>.reverse.eager; put $countdown.^name; # Seq put $countdown.elems; # 5 It should read my $countdown = <1 2 3 4 5>.reverse.eager; put $countdown.^name; # List put $countdown.elems; # 5

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Some spacing needed in "[POSITION]is a postcircumfix..."

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In the sentence "It takes a starting index, a length, and the items to remove from the list." about .splice, doesn't the last parameter in .splice specify the items with which to replace the removed elements? From the doc: multi method splice(Array:D: $start = 0, $elems?, *@replacement --> Array) Deletes $elems elements starting from index $start from the Array, returns them and replaces them by @replacement.

Note from the Author or Editor:
change "remove from list" to "add to list"

The code sample reads: my $list = ( 1; 'Hamadryas'; 'a', 'b' ); put $list.elems; # 3 say $list; # (1 2 (a b)) put $list.[0].^name; # Int put $list.[1].^name; # Str put $list.[*-1].^name; # List It should read: my $list = ( 1; 'Hamadryas'; 'a', 'b' ); put $list.elems; # 3 say $list; # (1 Hamadryas (a b)) put $list.[0].^name; # Int put $list.[1].^name; # Str put $list.[*-1].^name; # List

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The page says: Each sublist has three elements: ((1 a 🐈)(2 b 🐇)(3 🐀)) but the last sublist only shows two. It should say Each sublist has three elements: ((1 a 🐈)(2 b 🐇)(3 c 🐀))

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Change as noted.

"What’s actually in $result?" should read "What’s actually in $value?"

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Misindented.

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Indent like so: Indent like so, with everything inside the try { ... } moved over four spaces: try { CATCH { when X::MyException { put 'Caught a custom error' } } my-own-error(); }

The snippet says my $result = do-something(); if $result { ... } my $did-it-work = ?$results; but it should probably say my $result = do-something(); if $result { ... } my $did-it-work = ?$result;

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change as noted

"It’s probably easiest to represent it as a decimal number" should read "It’s probably easiest to represent it as an octal number"

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Misplaced comma in "write, this".

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should be "as I write this," in note

The comment reads: # ((Any) perlicus Sostrata Junonia) However, 'perlicus' should be removed: # ((Any) Sostrata Junonia)

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This is actually on page 105 (Chapter 6, "Changing a Single Element") the third to last code block should read: my $butterflies = ( $, 'Sostrata', 'Junonia' ); say $butterflies; # ((Any) Sostrata Junonia)

In the code snippet: my Buf $buffer = $fh->read( $count ); the pointy block arrow (->) is used to invoke the `read` method. However, a dot (.) should be used instead.

Note from the Author or Editor:
Change my Buf $buffer = $fh->read( $count ); to my Buf $buffer = $fh.read( $count );

The variable names read better as @permissible... instead of @permissable...

Note from the Author or Editor:
Change all instances of @permissable to @permissible

%color should be %color-name-to-rgb.

Note from the Author or Editor:
Change all instances of %color on that page to %color-name-to-rgb

multi subsomething ( $a ) { put "One argument"; } multi subsomething ( $a, $b ) { put "Two arguments"; } should read multi sub something ( $a ) { put "One argument"; } multi sub something ( $a, $b ) { put "Two arguments"; }

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change as noted

The example on the previous page is: "You call .reverse on a List to flip the list around. When you call List methods it just works: my $countdown = <1 2 3 4 5>.reverse; put $countdown.^name; # Seq put $countdown.elems; # 5” On the next page the first line is "The result isn’t actually a Seq, but in most common cases that isn’t important." I think it should say that the result *IS* actually a Seq.

Note from the Author or Editor:
Change to read "The result is actually a Seq"

The '+' should be a '*'.

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Change as noted to "3 * 3"

operaters -> operators

The current sentence is "This like your basic number-guessing program, but you have to make two sets of comparisons." It should probably be "This is like your basic number-guessing program, but you have to make two sets of comparisons." The word "is" should be added after the word "This".

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Change as noted.

sub MAIN ( $thingy1, $thingy2 ) { put '1: ', $thingy1; put '2: ', $thingy1; } You probably intended: sub MAIN ( $thingy1, $thingy2 ) { put '1: ', $thingy1; put '2: ', $thingy2; }

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Subset::Common *** should be Subsets::Common

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Change as noted