I'm not familiar with character sets and whether languages pick them up from their environments or if they are baked into the language itself, I wanted to make a simple number system in dart that has the largest possible base it can have, like hex has 0-9a-f I would have every single character in some specified ascending order with lower case and upper case having different values to give me the largest possible base to my number system. I want to do this so I can send numbers as strings with as few characters as possible, so my question is, does dart have a standard baked in character set that I can be certain will exist in every environment it runs in?
You should be able to use every value even if no concrete character is assigned to a code.
This would only be a problem when you try to display the character.
Some codes are control characters with special meaning (like 0x0000) which you should avoid
more info here: http://www.unicode.org/Public/UNIDATA/UnicodeData.txt.
If you want to transport the result over the internet using text protocols you may be limited to ASCII. In this case I suggest Base64 encoding.
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Subject says it all. Been looking for an answer, but cannot seem to find it.
I am writing a web app that will store data in a database and also have language files translated into a wide variety of character sets. At various moments, the text will be presented. I want to control presentation such as spurious blank spaces at the beginning and end of strings. Also I want to ensure some letters are upper or lower case.
My question is: what happens in upper/lower case functions when the character set only has one case?
EDIT Sub question: Are there any unexpected side effects to be aware of?
My guess is that you simply get back the one and only character.
EDIT - Added Description
The main reason for asking this question is that I am writing a webapp that will be distributed and run on machines in remote areas with little or no chance to fix "on-the-spot" bugs. It's not a complicated webapp, but will run with many different language char sets. I want to be certain of my footing before releasing the server.
First of all the upper() and lower() method in python can be applied to Hindi, Amharric and non-letter character sets.
For instance will the upper() method converts the lowercase characters if an equivalent uppercase of this char exists. If not, then not.
Or better said, if there is nothing to convert, it stays the same.
If I have a string "\u05D2\u0308" I don't actually get a diaeresis on top of a gimel. It sits to the side, as a discrete glyph.
I don't actually want the combined glyph, but I'm confused in general. How does a combining diacritic like U+0308 decide whether to combine with the preceeding character or hang out on its own?
And how much of this behavior is specified in the unicode standard and how much is up to the individual text renderer or font?
Actually, it does combine.
You are perhaps using some environment where the text engine fails to render this correctly, but in fact your string is one character long (using the conventional sense of "character"), and a correct Unicode-compliant environment will tell you so.
I'm curious about the way that in the past it was implemented and I want to get information about how can I implement a character set of my own.
ASCII (American Standard Code for Information Interchange) was the "original" characterset, and remains the basis for most text data. ASCII is actually a 7-bit code (the numeric values range from 0 to 127) with the most significant bit of a byte indicating if the rest of the byte refers to ASCII (if zero) or the current Codepage.
Extra (non-ascii) characters were then added to these codepages, and the user's computer would load a specific codepage to use. Unfortunately this meant that you needed to load the correct codepage before viewing a file or the wrong characters would appear.
We have now moved on, and most systems use Unicode which is a variable character length (rather than the single-byte characters used previously) which can contain thousands upon thousands of characters, allowing for a single encoding to cater for what would have been multiple codepages using the ASCII+Codepage method of old.
That's the brief history; As to how to create your own characterset, I'm not sure what you are trying to achieve - You can create your own fonts, but if you're talking about an actual characterset (i.e. characters that do not already exist) then you'll have to get your characterset added to a standard such as Unicode so that other computers can make use of your new characters, which would be a considerable amount of work (and I have no idea how you'd even go about it) -- It's worth considering, however, that almost every character in existence already exists in Unicode so you may want to review what's already been done before you try and take on a mammoth undertaking such as creating an entirely new characterset.
When working in the Moovweb SDK, length("çãêá") is expected to return 4, but instead returns 8. How can I ensure that the length function works correctly when using Unicode characters?
This is a common issue with Unicode characters and the length() function using the wrong character set. To fix it you need to set the charset_determined variable to make sure the correct character set is being used before making the call to length(), like so in your tritium code:
$charset_determined = "utf-8"
# your call to length() here
In Unicode, there is no such thing as a length of a string or "number of characters". All this comes from ASCII thinking.
You can choose from one of the following, depending what you exactly need:
For cursor movement, text selection and alike, grapheme clusters shall be used.
For limiting the length of a string in input fields, file formats, protocols, or databases, the length is measured in code units of some predetermined encoding. The reason is that any length limit is derived from the fixed amount of memory allocated for the string at a lower level, be it in memory, disk or in a particular data structure.
The size of the string as it appears on the screen is unrelated to the number of code points in the string. One has to communicate with the rendering engine for this. Code points do not occupy one column even in monospace fonts and terminals. POSIX takes this into account.
There is more info in http://utf8everywhere.org
I have built a set of scripts, part of which transform XML documents from one vocabulary to a subset of the document in another vocabulary.
For reasons that are opaque to me, but apparently non-negotiable, the target platform (Java-based) requires the output document to have 'encoding="UTF-8"' in the XML declaration, but some special characters within text nodes must be encoded with their hex unicode value - e.g. '”' must be replaced with '”' and so forth. I have not been able to acquire a definitive list of which chars must be encoded, but it does not appear to be as simple as "all non-ASCII".
Currently, I have a horrid mess of VBScript using ADODB to directly check each line of the output file after processing, and replace characters where necessary. This is painfully slow, and unsurprisingly some characters get missed (and are consequently nuked by the target platform).
While I could waste time "refining" the VBScript, the long-term aim is to get rid of that entirely, and I'm sure there must be a faster and more accurate way of achieving this, ideally within the XSLT stage itself.
Can anyone suggest any fruitful avenues of investigation?
(edit: I'm not convinced that character maps are the answer - I've looked at them before, and unless I'm mistaken, since my input could conceivably contain any unicode character, I would need to have a map containing all of them except the ones I don't want encoded...)
<xsl:output encoding="us-ascii"/>
Tells the serialiser that it has to produce ASCII-compatible output. That should force it to produce character references for all non-ASCII characters in text content and attribute values. (Should there be non-ASCII in other places like tag or attribute names, serialisation will fail.)
Well with XSLT 2.0 you have tagged your post with you can use a character map, see http://www.w3.org/TR/xslt20/#character-maps.