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Scala: How to use higher-order functions with Option (instead of match expressions)

Table of Contents1 - Sample data2 - From match expressions to higher-order functions3 - Notes4 - Resources5 - Comments

I originally wrote a long introduction to this article about Scala Options, but I decided to keep that introduction for a future second article in this series. For this article I’ll just say:

  • idiomatic Scala code involves never using null values
  • because you never use nulls, it’s important for you to become an expert at using Option, Some, and None
  • initially you may want to use match expressions to handle Option values
  • as you become more proficient with Scala and Options, you’ll find that match expressions tend to be verbose
  • becoming proficient with higher-order functions (HOFs) like map, filter, fold, and many others are the cure for that verbosity

How to determine if a Scala String contains a regular expression pattern

Scala String FAQ: How can you determine whether a String contains a regular expression pattern in Scala? (Or, “How can I find the first match (or all matches) of a regex in a String?”)

Solution

Create a Regex object by invoking the .r method on a String, and then use that pattern with findFirstIn when you’re looking for one match, and findAllIn when looking for all matches.

A Perl array 'contains' example

Perl array FAQ: How can I test to see if a Perl array already contains a given value? (Also written as, How do I search an array with the Perl grep function?)

I use the Perl grep function to see if a Perl array contains a given entry. For instance, in this Perl code:

The Perl exists function - test to see if a hash key exists

Perl "hash key exists" FAQ: How can I test to see if a key exists in a Perl hash?

Many times when working with a Perl hash, you need to know if a certain key already exists in the hash. The Perl exists function lets you easily determine if a key already exists in the hash.

A Ruby substring example

Ruby substring FAQ: I can't find a Ruby substring method, how can I tell if one Ruby string contains another string?

Solution: I expected the Ruby String class to include a method named substring, but it doesn't. My personal disappointment aside, it does have a method named include? that works the way I expected it to. Here's a simple example, using the irbenvironment to perform a few tests.