[erlang-questions] Erlang basic doubts about String, message passing and context switching overhead

Oliver Korpilla <>
Sat Jan 14 16:53:01 CET 2017


Could the Unicode support in elixir serve as a starting point?

https://hexdocs.pm/elixir/1.3.3/String.html#content

String.upcase/1 and String.downcase/1 seem to be Unicode-aware. And a lot of effort seems have gone in scenarios like this:

"For example, the codepoint “é” is two bytes:

iex> byte_size("é")
2"

Given that both Erlang and elixir are implemented on top of BEAM, the wheel might not need reinventing? I know engineers and programmers love inventing stuff, and this discussion seems to point in that direction, but...

Cheers,
Oliver
 
 

Gesendet: Freitag, 13. Januar 2017 um 23:34 Uhr
Von: "Michał Muskała" <>
An: "Richard A. O'Keefe" <>, "Steve Davis" <>, , "Jesper Louis Andersen" <>
Cc: "Erlang Questions" <>
Betreff: Re: [erlang-questions] Erlang basic doubts about String, message passing and context switching overhead

I fully agree there are no languages that deal with strings perfectly. That said there are those that are better at it and those that aren't so good. A language, where I need to look for a library to upcase or downcase my own name, fits into the second group in my book.

Michał.
On 13 Jan 2017, 13:20 +0100, Jesper Louis Andersen <>, wrote:

Richard is indeed right, depending on what your definition of "String" is.
 If a "String" is "An array of characters from some alphabet", then you need to take into account Strings are Unicode codepoints in practice. This is also the most precise definition from a technical point of view.
 When I wrote my post, I was--probably incorrectly--assuming the older notion of a "String" where the representation is either ASCII or something like ISO-8859-15. In this case, a string coincides with a stream of bytes.
 Data needs parsing. A lot of data comes in as some kind of stringy representation: UTF-8, byte array (binary), and so on.
 And of course, that isn't the whole story, since there are examples of input which are not string-like in their forms.
  

On Fri, Jan 13, 2017 at 2:34 AM Richard A. O'Keefe <[mailto:]> wrote:

On 13/01/17 8:56 AM, Jesper Louis Andersen wrote:
> Strings are really just streams of bytes.

That was true a long time ago.  Maybe.
But it isn't anywhere near accurate as a description
of Unicode:
  - Unicode is made of 21-bit code points, not bytes.
  - Most possible code points are not defined.
  - Some of those that are defined are defined as
    "it is illegal to use this".
  - Unicode sequences have *structure*; it is simply
    not the case that every sequence of allowable
    Unicode code points is a legal Unicode string.
  - As a special case of that, if s is a non-empty
    valid Unicode string, it is not true that every
    substring of s is a valid Unicode string.

In case you were thinking of UTF-8, not all byte
sequences are valid UTF-8.

Byte streams are as important as you say, but it's
really hard to see the software for a radar or a
radio telescope as processing strings...
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