On 22/01/2014, at 10:23 PM, Joachim Breitner wrote:
Am Mittwoch, den 22.01.2014, 14:56 +1300 schrieb Richard A. O'Keefe:
If there is _any_ sane way to reverse a Unicode string, which I rather doubt, it would be _horrible_ to implement it.
I suggest this:
reverse unicode_str = '\u202E' : unicode_str
It works great!
According to "Unicode Demystified", The Unicode bidirectional text layout algorithm (or "bi-di algorithm," as it is most commonly called) is possibly the most complicated and difficult-to- understand aspect of the Unicode standard. Considering the rest of Unicode, that says a LOT. This particular example using RIGHT-TO-LEFT OVERRIDE is a neat hack, but as a *general* way to reverse strings it's a FAIL: let s="\u202DIt's harder than you think." '\u202E' : s You will see no reversal in the output. Reverting to the original topic, Maybe and Either signify different things to human beings, and in the original libraries, the cost of having both was negligible compared with the benefits. Just recently I was revising some code in another language, where they had the equivalent of infinity = 99999.0 to serve as the initial value in a "search for the cheapest element and its cost" loop, and I suggested the equivalent of using Maybe (Cost, Item) instead, on the grounds that when you make up an "arbitrary" value it's a bad sign. In fact making this change led me to a deeper understanding of what the algorithm could do and a clarifying shift in its structure. (Amongst other things, the original code actually _relied_ on infinity + finite > infinity, which is not the way infinities are supposed to behave.) Representing Maybe as Either with an arbitrary value made up to be the "missing" value seems to me like just such a bad sign.