CharsetEncoder#canEncode() equivalent for PowerShell

Context:

You want to test whether a codepoint is valid in a specific character encoding.

Problem

In .NET, there are no equivalent functions to CharsetEncoder#canEncode() in Java.

Solution

If you want to test whether a character is valid in an encoding, you can test by using character interconversion like:

function Test-Character {
  Param(
    [Parameter(ValueFromPipeline=$true,Mandatory=$true)]
    [string] $Character,
    [Parameter(ValueFromPipeline=$false,Mandatory=$true)]
    $Encoding
  )
  begin {
    if ($PSVersionTable.PSEdition -eq "Core") {
      [System.Text.Encoding]::RegisterProvider([System.Text.CodePagesEncodingProvider]::Instance)
    }
    $TestEncoding = [System.Text.Encoding]::GetEncoding($Encoding)
  }
  process {
    [String]::new($TestEncoding.GetChars($TestEncoding.GetBytes($Character))).Equals($Character)  
  }
}

You can call this like Test-Character -Character "あ" -Encoding 932 and will get $True, and Test-Character -Character "♩" -Encoding 932 and will get $False. This cmdlet is suitable for test whether a character valid in Unicode is valid in another encoding.

Also, you can test codepoints with Convert-CodePoint like:

function Test-CodePoint {
  Param(
    [Parameter(ValueFromPipeline=$true,Mandatory=$true)]
    [string] $CodePoint,
    [Parameter(ValueFromPipeline=$false,Mandatory=$true)]
    $Encoding
  )
  begin {
    [System.Text.Encoding]::RegisterProvider([System.Text.CodePagesEncodingProvider]::Instance)
  }
  process {
    $UnicodeCodePoint = (Convert-CodePoint -CodePoint $CodePoint -From $Encoding -To "utf-16BE")
    $ReverseCodePoint = (Convert-CodePoint -CodePoint $UnicodeCodePoint -From "utf-16BE" -To $Encoding)
    $CodePoint.Equals($ReverseCodePoint)
  }
}

You can call this like Test-CodePoint -CodePoint "84BE" -Encoding 932 and will get $True, and Test-CodePoint -CodePoint "84BF" -Encoding 932 and will get $False. This cmdlet is suitable for test whether a codepoint is valid in an encoding.

子の名に使える非漢字

「子の名に使える漢字」は法務省に一覧表があるが、「子の名に使える非漢字」については一覧表のようななものがない。
「あ」や「ア」のような一般的なひらがな・カタカナは当たり前に使えるとして、日本の文字コードの規格であるJIS X 0208およびJIS X 0213の中には、日常あまり使わないひらがな・カタカナや、かな文字とも漢字とも言えない文字がいろいろ載っている。
そこで、子の名に使えるんだか使えないんだかよくわからない文字について、実際に使えるのか使えないのか調べてみた。

判断には法務省の戸籍統一文字情報のページを使用する。このページで文字を検索し、個別の文字のページで、「文字区分」の欄に「子の名に使える文字」と記載があれば、その文字は子の名に使えるということになる。

#	文字	コード	戸籍統一文字	子の名に使える	戸籍統一文字番号
1	ゎ	U+308E	Yes	Yes	905250
2	ゔ	U+3094	No	No
3	ゕ	U+3095	No	No
4	ゖ	U+3096	No	No
5	ゝ	U+309D	Yes	Yes	901890
6	ゞ	U+309E	Yes	Yes	901900
7	ヮ	U+30EE	Yes	Yes	906160
8	ヴ	U+30F4	Yes	Yes	906220
9	ヵ	U+30F5	Yes	Yes	906230
10	ヶ	U+30F6	Yes	Yes	906240
11	ヷ	U+30F7	No	No
12	ヸ	U+30F8	No	No
13	ヹ	U+30F9	No	No
14	ヺ	U+30FA	No	No
15	ヽ	U+30FD	Yes	No	901870
16	ヾ	U+30FE	Yes	No	901880
17	〃	U+3003	Yes	No	901910
18	仝	U+4EDD	Yes	No	901920
19	々	U+3005	Yes	Yes	901930

Meanings of :owner, :repo, ... in GitHub API document

In GitHub API document (ex. https://developer.github.com/v3/repos/ ), examples of how to access API showed like GET /repos/:owner/:repo/contributors. Meanings of indicator variable-like valiables such as :owner, :repo are listed below:

#	variable	meanings
1	:owner	username, or name of organization in GitHub Enterprise
2	:repo	name of repository
3	:number	sequence number of pull request or issue (the sequence is shared by pull requests and issues)
4	:id	ID of comment, etc.
5	:sha	SHA-1 hash of a commit
6	:ref	Path to a reference (heads/BranchA for a branch named BranchA)

How to convert string to number with AngularJS

There is more than one way to convert string to number in JavaScript.

Context:

• Use AngularJS to bind text boxes to variables.
• Sum up input values in some text boxes.
• Omit ng-required, ng-pattern, ng-minlength, ng-maxlength, etc., wherever possible.
• Use {{~}} to print summed up value.
• Should handle values larget than 32-bit integer.
• String “45a”, “0xAB”, “-0xDE”, “2e4”, and “Inifinity” should be treated as illegal value (NaN) or 0.

Comparison:

There is no only neat things to do …

• parseInt(value, 10) … Convert “45a” to 45, “0xAB” to 171, “-0xDE” to -222, and “2e4” to 2. Could not be used in AngularJS {{ ~ }} because it create a new object.
• parseFloat(value) … Convert “45a” to 45, “2e4” to 20000, and “Infinity” to Infinity. Could not be used in AngularJS {{ ~ }} because it create a new object.
• Number(value) … Convert “0xAB” to 171, and “Infinity” to Infinity. Could not be used in AngularJS {{ ~ }} because it create a new object.
• value|0, value>>0, value<<0, … Convert “0xAB” to 171, and “2e4” to 20000. Cannot handle value larger than 2³¹ (=2147483648).
• +value … Convert “0xAB” to 171, “2e4” to 20000, and “Infinity” to Infinity. {{ (+a) + (+b) | number }} is treated as string concat on AngularJS 1.2.1 (no problem on AngularJS 1.4.8)
• value*1 … Convert “0xAB” to 171, “2e4” to 20000, and “Infinity” to Infinity. {{ undefined*1 }} becomes NaN on AngularJS 1.4.8 (no problem on JavaScript console…)
• value-0 … Convert “0xAB” to 171, “2e4” to 20000, and “Infinity” to Infinity.

Comparison of these code on some values: http://jsfiddle.net/satob/fu1sjtmd/

To treat “0xAB”, “-0xDE”, “2e4”, and “Inifinity” as illiegal value, you should use ng-pattern to cutoff non-digit characters like this: http://jsfiddle.net/satob/8oeLfLrz/

URL of GitHub Enterprise API is different from github.com's one

Problem:

I have tried to access GitHub Enterprise API with a URL like showed below, based on examples from some websites, but the response was 404 error.

https://x.x.x.x/repos/Project/Repository/git/refs/heads

Reason:

URL of GitHub Enterprise API is different from github.com’s one. github’s API URL is like:

https://api.github.com/repos/User/Repository/git/refs/heads

and GitHub Enterprise API URL is like:

https://x.x.x.x/api/v3/repos/Project/Repository/git/refs/heads

Solution:

Fix the URL and got response successfully.