String index doc

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Flyzone
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Joined: Nov 17, 2017 17:39

String index doc

Postby Flyzone » Feb 28, 2021 22:44

The String index ( [ ] ) documentation is entirely too vague in describing the operator's return value. It specifies a "reference" which apparently is an ASCII value for the selected character. It should state this. This return value is not further elaborated on in the Description either. One might infer this return value from the example but that's just poor. My own notion of a "reference" is usually an address pointer.

Operator [] (String index)
Returns a reference to a character in a string
badidea
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Re: String index doc

Postby badidea » Feb 28, 2021 23:33

You mean this page: https://freebasic.net/wiki/KeyPgOpStringIndex
I agree that it is confusing. The term 'reference' is there since the creation of this page in 2008.
I'll wait for fxm to fix/improve it, else I will try tomorrow.
Flyzone
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Joined: Nov 17, 2017 17:39

Re: String index doc

Postby Flyzone » Feb 28, 2021 23:39

Yes. That is the page. Sorry I didn't post the link.

<<is there since the creation of this page in 2008.>>

... I guess I'm the only dummy - so no rush, but Tnx.
fxm
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Re: String index doc

Postby fxm » Mar 01, 2021 6:32

'Returns a reference' is the right term because the 'Operator [] (String Index)' really returns by reference (see Syntax).

"Returns a reference" is very precise, and this is an important term that one needs to know well (see Reference in Glossary):
- 'Return by reference' is the opposite of 'return by value' where only a copy is returned. When a variable is returned by reference, you can modify it.
- 'Return by reference' is implemented under the hood as a pointer implicitly dereferenced.

- In case of a 'String' or a 'ZString' 's':
s[n]
is equivalent to:
*Cptr(Ubyte Ptr, Strptr(s) + n)

- In case of a 'WString' 's':
s[n]
is equivalent to:
*Cptr(T Ptr, Strptr(s) + n)

The text 'Returns a reference to a character in a string' could also be improved with roughly:
'Returns a reference to a numeric character in a string':
- for a 'String' or a 'ZString': a 'Ubyte' (containing the ASCII value of the character),
- for a 'WString': a numeric type depending on platform, for example 'UShort' for Windows or 'ULong' for Linux (containing the numeric value of the character).

This afternoon, I will update the documentation page as per everything stated above.


[edit]
Done:
KeyPgOpStringIndex → fxm [complemented description and example]
Flyzone
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Joined: Nov 17, 2017 17:39

Re: String index doc

Postby Flyzone » Mar 01, 2021 13:39

Though you've solved the original problem with an explanation of the return values, I still find the statement:
"Returns a reference to a numeric character in a string"
at best obscure, and perhaps even misleading to those who might actually need the documentation.
But Thanks for the fix.
fxm
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Re: String index doc

Postby fxm » Mar 01, 2021 14:03

Maybe it would be better like this?
Returns a numeric reference to a character value in a string

Anyway, if it's the term 'reference' that bothers you, we can't escape it because it's the appropriate term!
MrSwiss
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Re: String index doc

Postby MrSwiss » Mar 01, 2021 14:40

fxm wrote:Maybe it would be better like this?
Returns a numeric reference to a character value in a string

Anyway, if it's the term 'reference' that bothers you, we can't escape it because it's the appropriate term!
I beg to differ, how it is returned is only a secondary priority.
Ordinary users want to know, what they get:

A UByte containing the ASCII value of a string-character (byref return).
fxm
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Re: String index doc

Postby fxm » Mar 01, 2021 15:00

First, one should extend your proposition to WStrings:
A numeric type containing the value of a string-character (byref return)
to compare to:
Returns a numeric reference to a character value in a string

I prefer mine which is more compact and precise IMHO.
MrSwiss
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Re: String index doc

Postby MrSwiss » Mar 01, 2021 15:15

fxm wrote:I prefer mine which is more compact and precise IMHO.

I definitely don't: its more compact (yes) but far less simple to understand.
This is, what should have TOP PRIORITY. Secondly, users must like it (not you or me).

in its first form:
A UByte containing the ASCII value of a string-character (byref return).
in its second form:
A UShort containing the numeric value of a wstring-character (Windows).
or:
A ULong containing the numeric value of a wstring-character (Linux).

Btw: you've done that type of explanation yourself, many times over ...
fxm
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Re: String index doc

Postby fxm » Mar 01, 2021 15:23

UShort or ULong or ..... for WStrings, depending on platform!

The keyword manual should be the reference for the language, not a tutorial or beginner's documentation.
MrSwiss
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Re: String index doc

Postby MrSwiss » Mar 01, 2021 15:35

fxm wrote:UShort or ULong or ..... for WStrings, depending on platform! <-- metioned already!
The keyword manual should be the reference for the language.

We agree on that but only as long as that doesn't make it "incomprehensible" for most.
Flyzone
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Joined: Nov 17, 2017 17:39

Re: String index doc

Postby Flyzone » Mar 01, 2021 16:02

I think MrSwiss is much closer to understanding the real problem as well as the audience. That is an understandable definition upon which the rest of the explanation builds. We have the classic chicken and egg problem, or which comes first - the WHAT or the HOW.
jj2007
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Re: String index doc

Postby jj2007 » Mar 01, 2021 17:13

fxm wrote:'Returns a reference' is the right term because the 'Operator [] (String Index)' really returns by reference (see Syntax).
Maybe it returns (arguably) something by reference, but it does not return a reference; it returns the numeric value of the char inside the string a at position n:

Code: Select all

Dim a As String = "Hello, world!"
Dim c As Integer=a[6]
print "char=[";a[6];"][";c;"]"

Dim ref as any ptr=@a[6]
print "ref=[";@a[6];"][";ref;"]"
Sleep
The BASIC syntax, btw, is c=Asc(Mid$(a, 6, 1)).
fxm
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Location: Paris suburbs, FRANCE

Re: String index doc

Postby fxm » Mar 01, 2021 17:35

Under the hood, its returns a pointer by value, which is implicitly dereferenced.
It is exactly the definition of a reference in FreeBASIC (an internal pointer implicitly dereferenced).

See in the Programmer's Guide my two articles in the topic 'Variables and Datatypes / References'.
Flyzone
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Joined: Nov 17, 2017 17:39

Re: String index doc

Postby Flyzone » Mar 01, 2021 19:43

jj2007 wrote:it returns (arguably) something by reference, but it does not return a reference; it returns the numeric value of the char inside the string a at position n


Precisely.

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