Perl 6 Operator Tablet

Herbert Breunung — Tue, 17 Apr 2012 00:56:19 -0000

Intro - Chapter: 0:History 1:Design 2:Basics 3:Var 4:Op 5:IO 6:Block 7:Sub 8:OOP 9:Rx 10:Meta
Overview - Appendix: A:Index B:Tables C:Cook D:Delta E:Best of F:Links G:Glossary

Perl folklore: Perl is an operator based language.

Perl 6 has a huge amount of operators, because they support 2 of the main design goals: they offer dense and readable code. 2 + 3 is certainly shorter and easier to understand then add(2,3), since pictograms can be picked up faster than words. (Fortran made his whole carrier on that). But because they are so many, they had to be sorted by a rule named huffman coding, which was applied here more than in any other part of the syntax.

To understand an operator you have to know his arity (how many parameters he takes - usually one (!) or two (+) ).

The precedence tells which operator to prefer in case of conflict, when no braces are used (round braces are only used for grouping and managing precedence). It allows 2 + 3 * 5 to return 17, not 25, which would upset your math teacher.

Behind that link is a table which also tells you also the associativity of every operator. This tells you after which rule to resolve precedence if one operator is used several times like in 2 * 3 * 7.

Comparison

Smartmatch

This is the most mighty (much more mighty than its backported Perl 5 twin) of all Perl 6 operators. It can be called the "compare-this-with-that-operator". If the left side of that infix op matches somehow the content of the right side, it returns Bool::True, otherwise Bool::False. The negated form !~ naturally works the other way around. The exact comparison operation depends on the data types of the values on both sides. Just look into that large table to check your specific case.

Smartmatching was originally invented to make matching with regex semantically sane.

~~ !~

Equality

eqv eq == ===
!= !==

Traversing Sequence

++ -- succ pred

sequence generation

Generic Comparison

before after cmp

Numerical Comparison

< == > <=> <= >=

String Comparison

lt eq gt leg le ge

joined comparison

3 < $a == $a < 7

is not the same as

3 < $a < 7

because latter is evaled at once and the first in 2 steps (left to right)

Junctions

| & ^ !
any all one none

Ranges

.. ^

logical selection

&& - and
|| - or
// - err
^^ - xor

ternary

?? !!

flipflop

ff fff

file test

table

yadda

...
???
!!!

context forcing scalar ops

bool context

? !
?& ?| ?^

numeric context

+ - * ** / % %%
+& +| +^ +< +>
mod exp sqrt sin cos tan log log10

numerical selection

min max minmax

String context

~ x
~& ~| ~^ ~< ~>

Ops for arrays/lists

List generation

The simplest way to create a list is by repeating some values:

'munch' xx 3 # results in 'munch', 'munch', 'munch'
('hallo', 'echo') xx 2 --> 'hallo', 'echo', 'hallo', 'echo'

In list context the range operator produces lists:

@ 2 .. 7 --> 2,3,4,5,6,7

Sequence Operator

...

traversing sequence

Zip

Z

Combinators

X

Hyperops

<< >>

Reduce

[ ]

Triangle

[\ ]

Feed Ops

<== ==>
<<== ==>>

Assignment ops

self assigning ops

precedence table

is in Appendix B

intentionally not existing ops

making own operators