Kotlin has very useful extensions functions for working with collections.
These extension functions make working with collections more easy and fun.
One of the extension functions is the random function.
When you call random() Kotlin returns a single element from the collection using the default random source.
The function also accepts a Random instance as argument.
This instance has a seeded value to return repeatable random values.
Sometimes you want to transform only the keys in a Map, or only transform the values.
Kotlin has two useful methods to achieve this: mapKeys and mapValues.
You can use mapKeys to transform the keys of the map while keeping the values the same.
With mapValues you can transform the values of the map while keeping the keys the same.
Both methods accept a lambda function as asrgument of type Map.Entry and must return the new key or value.
In order to transform the keys or values and add the result to an existing Map you can use the methods mapKeysTo and mapValuesTo.
The first argument is the existing (mutable) Map and the second argument is the lambda function.
In a previous blogpost you can learn about the semver command in Nushell to transform a string value into a semver type.
The command has a subcommand match-req.
You can use this command to check if a version matches part of the semantic version parts.
The result is a boolean value.
The version to compare with doesn’t have to defined fully, but could exist of only the major, minor or patch parts.
The value you pass can also be used to check if a version is greater or smaller than a given version.
A range with a lower and upper version to match on can be defined as well.
The boundary values are separated by a comma.
The semver Nushell plugin can be used to work with string values as semver type as you can see in a previous post.
You can use the semver sort command to sort string values with ordering rules for semantic versions.
With natural ordering of string values a value of 10.0.1 is placed before 2.1.0, but if you use semver sort the ordering will be correct.
The command will look at all the parts of the semver type.
So a major version of 2 is placed before 10.
If the major version part is the same than the minor part is used for ordering and so on.
To sort in descending order you can use the option --reverse or the short option -r.
In a previous blogpost you can learn about the semver command in Nushell to transform a string value into a semver type.
With the semver bump command you can increase one of the components of the semver type.
For example to increase the major version part you can use semver bump major.
This command will also update the minor and patch parts if needed.
The result is a semver type and you can use into value to transform it to a string type.
Nushell can be extended with plugins to have more functionality or types that are not part of standard Nushell.
If you want to work with string values that are actually semantic version values (https://semver.org) you can use the Nushell SemVer plugin.
The plugin must be added to Nushell by using the command plugin add <location of plugin>.
You can check with plugin list command if the plugin is available.
This command also shows commands that the plugin adds to Nushell.
The command into semver can be used to convert string values into a semver type.
The semver type has 5 properties: major, minor, patch, pre and build.
You can use dot notation to get the values for these properties or use the get command.
In the following command a string value is transformed to a semver type: let v = '4.0.2' | into semver.
And with $v.major you can extract the major part of the semver value and it returns 4.
Records with the keys major, minor, patch, pre and build can be transformed to a semver string with the semver from-record command.
And to transform a semver type to a record you can use the command semver into-record.
A Java text block is an easy way to have a multiline string value.
But there is a catch if we want to use a text block with the assertion method isEqualTo.
Suppose you have written a piece of code that create a new string value where the line endings are defined using System.lineSeparator().
The string value would have the line ending \n on Linux and MacOS systems, and the line ending \r\n on Windows system.
But a Java text block will always use the line ending \n on every platform, including the Windows platform.
If you would run your tests on a Windows platform then the assertion using isEqualTo will fail, but the test will pass on Linux or MacOS systems.
This is a problem if you are working with developers using different operating systems.
Therefore it is better to use the method isEqualToNormalizingNewlines for these type of assertions.
AssertJ will make sure the line endings are the same and the tests will pass independent of the operating system the tests are run on.
Nushell has the in operator to check if a value is an element of list.
With the same in operator you can check if a string is a substring of another string.
And finally you can use the in operator to check if a key is in a record.
When you use the operator the value you want to check is defined before the operator and the list, other string or record is defined after the operator.
The not-in operator is the opposite of the in operator and checks if a value is not in list or other string or key in a record.
It is also possible to use the has and not-has operators to do the same checks, but the value you want to check is set after the operator.
The list, other string or record is set before the operator.
In order to calculate an average for a list of numbers, file sizes, durations, or range of numbers, or a table with columns containing numeric values you can use the math avg command.
This command is part of the math module of Nushell.
When the input is a list then the result is a single value with the average of all values in the list.
If you use a table as input the result is a record where the key is the column name and the value the average of all values in that column.
Finally it is possible to have a single value as input and the result is the same value obviously.
The math module in Nushell has a lot of useful commands to work with numeric values.
You can use the math sum command to calculate the sum of a multiple numeric values.
The input of the command can be a list of numbers, durations, file sizes, or a range or table with columns containing numeric values.
The result is a single numeric value with the sum of all values in the input.
The math sum command can also be used on a table with multiple numeric columns.
It will return a record with the sum of all values for each column.