PowerShell gives us a real CLI for Windows based around .Net stuff. I don't like the creation of a new shell language but I suppose it makes sense given that they want something C# like but not C# exactly since that's much to verbose and strict for a CLI. One of the functions you can override is the TabExpansion function which is used when you tab complete commands. I really like this and so I've added on to the standard implementation to support replacing a variable name with its value, tab completion of available commands, previous command history, and drive names (there not restricted to just one letter in PS).
Learning the new language was a bit of a chore but MSDN helped. A couple of things to note, a statement that has a return value that you don't do anything with is implicitly the return value for the current function. That's why there's no explicit return's in my TabExpansion function. Also, if you're TabExpansion function fails or returns nothing then the builtin TabExpansion function runs which does just filenames. This is why you can see that the standard TabExpansion function doesn't handle normal filenames: it does extra stuff (like method and property completion on variables that represent .Net objects) but if there's no fancy extra stuff to be done it lets the builtin one take a crack.
Here's my TabExpansion function. Probably has bugs, so watch out!
function EscapePath([string] $path, [string] $original)
{
if ($path.Contains(' ') -and !$original.Contains(' '))
{
'"' $path '"';
}
else
{
$path;
}
}
function PathRelativeTo($pathDest, $pathCurrent)
{
if ($pathDest.PSParentPath.ToString().EndsWith($pathCurrent.Path))
{
'.\' $pathDest.name;
}
else
{
$pathDest.FullName;
}
}
# This is the default function to use for tab expansion. It handles simple
# member expansion on variables, variable name expansion and parameter completion
# on commands. It doesn't understand strings so strings containing ; | ( or { may
# cause expansion to fail.
function TabExpansion($line, $lastWord)
{
switch -regex ($lastWord)
{
# Handle property and method expansion...
'(^.*)(\$(\w|\.) )\.(\w*)$' {
$method = [Management.Automation.PSMemberTypes] `
'Method,CodeMethod,ScriptMethod,ParameterizedProperty'
$base = $matches[1]
$expression = $matches[2]
Invoke-Expression ('$val=' $expression)
$pat = $matches[4] '*'
Get-Member -inputobject $val $pat | sort membertype,name |
where { $_.name -notmatch '^[gs]et_'} |
foreach {
if ($_.MemberType -band $method)
{
# Return a method...
$base $expression '.' $_.name '('
}
else {
# Return a property...
$base $expression '.' $_.name
}
}
break;
}
# Handle variable name expansion...
'(^.*\$)([\w\:]*)$' {
$prefix = $matches[1]
$varName = $matches[2]
foreach ($v in Get-Childitem ('variable:' $varName '*'))
{
if ($v.name -eq $varName)
{
$v.value
}
else
{
$prefix $v.name
}
}
break;
}
# Do completion on parameters...
'^-([\w0-9]*)' {
$pat = $matches[1] '*'
# extract the command name from the string
# first split the string into statements and pipeline elements
# This doesn't handle strings however.
$cmdlet = [regex]::Split($line, '[|;]')[-1]
# Extract the trailing unclosed block e.g. ls | foreach { cp
if ($cmdlet -match '\{([^\{\}]*)$')
{
$cmdlet = $matches[1]
}
# Extract the longest unclosed parenthetical expression...
if ($cmdlet -match '\(([^()]*)$')
{
$cmdlet = $matches[1]
}
# take the first space separated token of the remaining string
# as the command to look up. Trim any leading or trailing spaces
# so you don't get leading empty elements.
$cmdlet = $cmdlet.Trim().Split()[0]
# now get the info object for it...
$cmdlet = @(Get-Command -type 'cmdlet,alias' $cmdlet)[0]
# loop resolving aliases...
while ($cmdlet.CommandType -eq 'alias') {
$cmdlet = @(Get-Command -type 'cmdlet,alias' $cmdlet.Definition)[0]
}
# expand the parameter sets and emit the matching elements
foreach ($n in $cmdlet.ParameterSets | Select-Object -expand parameters)
{
$n = $n.name
if ($n -like $pat) { '-' $n }
}
break;
}
default {
$varNameStar = $lastWord '*';
foreach ($n in @(Get-Childitem $varNameStar))
{
$name = PathRelativeTo ($n) ($PWD);
if ($n.PSIsContainer)
{
EscapePath ($name '\') ($lastWord);
}
else
{
EscapePath ($name) ($lastWord);
}
}
if (!$varNameStar.Contains('\'))
{
foreach ($n in @(Get-Command $varNameStar))
{
if ($n.CommandType.ToString().Equals('Application'))
{
foreach ($ext in @((cat Env:PathExt).Split(';')))
{
if ($n.Path.ToString().ToLower().EndsWith(($ext).ToString().ToLower()))
{
EscapePath($n.Path) ($lastWord);
}
}
}
else
{
EscapePath($n.Name) ($lastWord);
}
}
foreach ($n in @(Get-psdrive $varNameStar))
{
EscapePath($n.name ":") ($lastWord);
}
}
foreach ($n in @(Get-History))
{
if ($n.CommandLine.StartsWith($line) -and $n.CommandLine -ne $line)
{
$lastWord $n.CommandLine.Substring($line.Length);
}
}
# Add the original string to the end of the expansion list.
$lastWord;
break;
}
}
}
I recently finished Braid, the Xbox Live game, and a comparison with Portal is helpful. From a screen shot Braid
looks like a normal 2D platformer, but that's like looking at a screen shot of Portal and saying its a first person shooter. While the scaffolding of the game-play may sort of fall into that
category, the games are actually about exploring the character's ability and solving puzzles. In Portal the ability is bending space and in Braid its bending time. However, whereas in Portal there
is one space bending mechanism, the portal gun, Braid's protagonist explores several different time bending techniques including, most prominently, reversing time, but also time dilation, multiple
time-lines, and other odd things.
Similar to the difference in game-play, while Portal has a strict simplicity to its visual style, Braid is much more ornate, like you're playing in an oil painting. Without seeing video of the game, or playing the demo (which is available for free on Xbox Live) its difficult to convey, but it is quite lovely and the animation adds quite a bit. Both games too are rather short leaving you just a bit hungry for more and have an interesting plot and an ending that I'd hate to spoil although Braid replaces Portal's humor with melancholy. If you enjoyed Portal and Twelve Monkeys then I'd recommend Braid.
![['Neverending story' by Alexandre Duret-Lutz. A framed photo of books with the droste effect applied. Licensed under creative commons.]](http://farm1.static.flickr.com/90/252757784_3de44cbeb4_m_d.jpg)
Information about URI Fragments, the portion of URIs
that follow the '#' at the end and that are used to navigate within a document, is scattered throughout various documents which I usually have to hunt down. Instead I'll link to them all here.
Definitions. Fragments are defined in the URI RFC which states that they're used to identify a secondary resource that is related to the primary resource identified by the URI as a subset of the primary, a view of the primary, or some other resource described by the primary. The interpretation of a fragment is based on the mime type of the primary resource. Tim Berners-Lee notes that determining fragment meaning from mime type is a problem because a single URI may contain a single fragment, however over HTTP a single URI can result in the same logical resource represented in different mime types. So there's one fragment but multiple mime types and so multiple interpretations of the one fragment. The URI RFC says that if an author has a single resource available in multiple mime types then the author must ensure that the various representations of a single resource must all resolve fragments to the same logical secondary resource. Depending on which mime types you're dealing with this is either not easy or not possible.
HTTP. In HTTP when URIs are used, the fragment is not included. The General Syntax section of the HTTP standard says it uses the definitions of 'URI-reference' (which includes the fragment), 'absoluteURI', and 'relativeURI' (which don't include the fragment) from the URI RFC. However, the 'URI-reference' term doesn't actually appear in the BNF for the protocol. Accordingly the headers like 'Request-URI', 'Content-Location', 'Location', and 'Referer' which include URIs are defined with 'absoluteURI' or 'relativeURI' and don't include the fragment. This is in keeping with the original fragment definition which says that the fragment is used as a view of the original resource and consequently only needed for resolution on the client. Additionally, the URI RFC explicitly notes that not including the fragment is a privacy feature such that page authors won't be able to stop clients from viewing whatever fragments the client chooses. This seems like an odd claim given that if the author wanted to selectively restrict access to portions of documents there are other options for them like breaking out the parts of a single resource to which the author wishes to restrict access into separate resources.
HTML. In HTML, the HTML mime type RFC defines HTML's fragment use which consists of fragments referring to elements with a corresponding 'id' attribute or one of a particular set of elements with a corresponding 'name' attribute. The HTML spec discusses fragment use additionally noting that the names and ids must be unique in the document and that they must consist of only US-ASCII characters. The ID and NAME attributes are further restricted in section 6 to only consist of alphanumerics, the hyphen, period, colon, and underscore. This is a subset of the characters allowed in the URI fragment so no encoding is discussed since technically its not needed. However, practically speaking, browsers like FireFox and Internet Explorer allow for names and ids containing characters outside of the defined set including characters that must be percent-encoded to appear in a URI fragment. The interpretation of percent-encoded characters in fragments for HTML documents is not consistent across browsers (or in some cases within the same browser) especially for the percent-encoded percent.
Text. Text/plain recently got a fragment definition that allows fragments to refer to particular lines or characters within a text document. The scheme no longer includes regular expressions, which disappointed me at first, but in retrospect is probably good idea for increasing the adoption of this fragment scheme and for avoiding the potential for ubiquitous DoS via regex. One of the authors also notes this on his blog. I look forward to the day when this scheme is widely implemented.
XML. XML has the XPointer framework to define its fragment structure as noted by the XML mime type definition. XPointer consists of a general scheme that contains subschemes that identify a subset of an XML document. Its too bad such a thing wasn't adopted for URI fragments in general to solve the problem of a single resource with multiple mime type representations. I wrote more about XPointer when I worked on hacking XPointer into IE.
SVG and MPEG. Through the Media Fragments Working Group I found a couple more fragment scheme definitions. SVG's fragment scheme is defined in the SVG documentation and looks similar to XML's. MPEG has one defined but I could only find it as an ISO document "Text of ISO/IEC FCD 21000-17 MPEG-12 FID" and not as an RFC which is a little disturbing.
AJAX. AJAX websites have used fragments as an escape hatch for two issues that I've seen. The first is getting a unique URL for versions of a page that are produced on the client by script. The fragment may be changed by script without forcing the page to reload. This goes outside the rules of the standards by using HTML fragments in a fashion not called out by the HTML spec. but it does seem to be inline with the spirit of the fragment in that it is a subview of the original resource and interpretted client side. The other hack-ier use of the fragment in AJAX is for cross domain communication. The basic idea is that different frames or windows may not communicate in normal fashions if they have different domains but they can view each other's URLs and accordingly can change their own fragments in order to send a message out to those who know where to look. IMO this is not inline with the spirit of the fragment but is rather a cool hack.
I've been at Microsoft three years as of last Thursday. It makes me feel old but on the bright side I've upgraded offices. I now
have an office with a window. Its actually a coincidence that I got this office at the time of my Microsoft anniversary but I like to pretend. I've had a single office for only four or five months
now so its a nice surprise that I'm moving into a single window office so soon.
Of course this move means I'll be leaving some things behind. For instance the hanging dry erase pen holder that I created out
of office supplies I will leave attached to my old white board. My new office has fancy whiteboards with trays built-in (sooo fancy) so I know the person coming into my old office will make better
use of my hanging dry erase pen holder then I would. I explained to him that the rubber bands need to be replaced every eight months or so and not to exceed the maximum weight restrictions.
Additionally, the office art masterpiece I created I will also leave behind. When Bill Gates was featured on the cover of
Diversity Inc. for his amazing philanthropic acts many of us got copies in our mailboxes. I
collected mine and some from the recycling bins and put up five of the covers on the wall. Eventually others added to it which was my intent, but I only started this when I eventually checked my
mailbox a week or so after the magazine arrived so there weren't as many covers left with which to work. At any rate I ended up with eleven on the wall. I'll leave the interpretation of the artwork
up to the viewer.
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