Advanced Exercism • powershell

Acronym

Challenge Overview

Convert a long phrase to its acronym.

Visit the acronym exercise on Exercism to read the full instructions and download the exercise files.

Dig Deeper

Regular expression

Using `regex`

Function Get-Acronym() {
    [CmdletBinding()]
    Param (
        [string]$Phrase
    )
    (-join ([regex]::Matches($Phrase, "\p{L}+'?\p{L}*") | ForEach-Object { $_.Value[0] })).ToUpper()
}

This approach use the regex class from .NET to match potential words inside the phrase using a specific pattern.

[regex]::Matches($Phrase, "\p{L}+'?\p{L}*")

The pattern match any regular word and those that have apostrophe inside it, for example doesn't or Halley's in a test case. We then collect the matched objects and loop over them, extracting the match value first index, which is the first char of each word.

ForEach-Object { $_.Value[0] }

Then we call the -join operator upon the collection to turn this into a string, and then call the string method .ToUpper() to make sure it is all in uppercase to fit with acronym behavior.

Regex expression for .NET

String methods

Using `string` methods

Function Get-Acronym() {
    [CmdletBinding()]
    Param (
        [string]$Phrase
    )
    ( $Phrase -replace "[-_]"," " -split " " | Foreach-Object {$_[0].ToString().ToUpper()} ) -join ""
}

Find and replace strings.
About Split operator.
About Join operator.

Loop and boolean

Using `foreach` loop and `boolean` values

Function Get-Acronym() {
    [CmdletBinding()]
    Param (
        [string]$Phrase
    )
    $newWord = $true
    foreach ($char in $Phrase.ToCharArray()) {
        if ($newWord -and $char -match "[a-z]") {
            $acronym += $char
            $newWord = $false
        }
        if (-not $newWord -and $char -match "[_\- ]") {
            $newWord = $true
        }
    }
    $acronym.ToUpper()
}

This approach use a flag with a boolean value to mark when a new word is about to begin or not.

    $newWord = $true

We then loop over the characters from the input using foreach and .ToCharArray() method. If we are about to start a new word (true) and the current char is a letter, then we add that letter to the result, and switch the flag to false. If we are not in phase of starting a new word (false) and the current char match one of the delimiters, then we switch the flag to true, signify that we are ready to start a new word.

    foreach ($char in $Phrase.ToCharArray()) {
        if ($newWord -and $char -match "[a-z]") {
            $acronym += $char
            $newWord = $false
        }
        if (-not $newWord -and $char -match "[_\- ]") {
            $newWord = $true
        }
    }
    $acronym.ToUpper()

After the loop is finished, we call ToUpper() method on the result and got our acronym in all capitalized letters.

Booleans.

Foreach loop.

Source: Exercism powershell/acronym