Hello Shawn
Just google with any programming language name and “string manipulation”
and you have enough reading for a week or so :o)
TedvGThat truly doesn't answer the question. It's not, “why do people index
strings with integers when that's the only tool they are given for
decomposing strings?” It's, “what do you have to do with strings that's
hard in Swift *because* you can't index them with integers?”
Hi Dave,
Ok. here are just a few examples:
Parsing and validating an ISBN code? or a (freight) container ID? or EAN13 perhaps?
of many of the typical combined article codes and product IDs that many factories and shops use?
or:
E.g. processing legacy files from IBM mainframes:
extract fields from ancient data records read from very old sequential files,
say, a product data record like this from a file from 1978 you’d have to unpack and process:
123534-09EVXD4568,991234,89ABCYELLOW12AGRAINESYTEMZ3453
into:
123, 534, -09, EVXD45, 68,99, 1234,99, ABC, YELLOW, 12A, GRAIN, ESYSTEM, Z3453.
product category, pcs, discount code, product code, price Yen, price $, class code, etc…
in Cobol and PL/1 records are nearly always defined with a fixed field layout like this.:
(storage was limited and very, very expensive, e.g. XML would be regarded as a
"scandalous waste" even the commas in CSV files! )
01 MAILING-RECORD.
05 COMPANY-NAME PIC X(30).
05 CONTACTS.
10 PRESIDENT.
15 LAST-NAME PIC X(15).
15 FIRST-NAME PIC X(8).
10 VP-MARKETING.
15 LAST-NAME PIC X(15).
15 FIRST-NAME PIC X(8).
10 ALTERNATE-CONTACT.
15 TITLE PIC X(10).
15 LAST-NAME PIC X(15).
15 FIRST-NAME PIC X(8).
05 ADDRESS PIC X(15).
05 CITY PIC X(15).
05 STATE PIC XX.
05 ZIP PIC 9(5).
These are all character data fields here, except for the numeric ZIP field , however in Cobol it can be treated like character data.
So here I am, having to get the data of these old Cobol production files
into a brand new Swift based accounting system of 2017, what can I do?
How do I unpack these records and being the data into a Swift structure or class?
(In Cobol I don’t have to because of the predefined fixed format record layout).
AFAIK there are no similar record structures with fixed fields like this available Swift?
So, the only way I can think of right now is to do it like this:
// mailingRecord is a Swift structure
struct MailingRecord
{
var companyName: String = “no Name”
var contacts: CompanyContacts
.
etc..
}
// recordStr was read here with ASCII encoding
// unpack data in to structure’s properties, in this case all are Strings
mailingRecord.companyName = recordStr[ 0..<30]
mailingRecord.contacts.president.lastName = recordStr[30..<45]
mailingRecord.contacts.president.firstName = recordStr[45..<53]
// and so on..
Ever worked for e.g. a bank with thousands of these files unchanged formats for years?
Any alternative, convenient en simpler methods in Swift present?
Kind Regards
TedvG
( example of the above Cobol record borrowed from here:
http://www.3480-3590-data-conversion.com/article-reading-cobol-layouts-1.html )
···
On 10 Feb 2017, at 00:11, Dave Abrahams <dabrahams@apple.com> wrote:
on Thu Feb 09 2017, "Ted F.A. van Gaalen" <tedvgiosdev-AT-gmail.com> wrote:
On 9 Feb 2017, at 16:48, Shawn Erickson <shawnce@gmail.com> wrote:
I also wonder what folks are actually doing that require indexing
into strings. I would love to see some real world examples of what
and why indexing into a string is needed. Who is the end consumer of
that string, etc.Do folks have so examples?
-Shawn
On Thu, Feb 9, 2017 at 6:56 AM Ted F.A. van Gaalen via swift-evolution <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
Hello Hooman
That invalidates my assumptions, thanks for evaluating
it's more complex than I thought.
Kind Regards
TedOn 8 Feb 2017, at 00:07, Hooman Mehr <hooman@mac.com <mailto:hooman@mac.com>> wrote:
On Feb 7, 2017, at 12:19 PM, Ted F.A. van Gaalen via swift-evolution <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
I now assume that:
1. -= a “plain” Unicode character (codepoint?) can result in one glyph.=-What do you mean by “plain”? Characters in some Unicode scripts are
by no means “plain”. They can affect (and be affected by) the
characters around them, they can cause glyphs around them to
rearrange or combine (like ligatures) or their visual
representation (glyph) may float in the same space as an adjacent
glyph (and seem to be part of the “host” glyph), etc. So, the
general relationship of a character and its corresponding glyph (if
there is one) is complex and depends on context and surroundings
characters.2. -= a grapheme cluster always results in just a single glyph, true? =-
False
3. The only thing that I can see on screen or print are glyphs (“carvings”,visual elements that stand on their own )
The visible effect might not be a visual shape. It may be for example, the way the surrounding shapes change or re-arrange.
4. In this context, a glyph is a humanly recognisable visual form of a character,
Not in a straightforward one to one fashion, not even in Latin / Roman script.
5. On this level (the glyph, what I can see as a user) it is not relevant and also not detectable
with how many Unicode scalars (codepoints ?), grapheme, or even on what kind
of encoding the glyph was based upon.False
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--
-Dave
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"