How to make use of single quotes?

[jclark]

Single quotes were used by symbolic string literals but are not any more.

Should we use them for something for which we are now using a less pleasant syntax? e.g.

• ^"xxx" delimited identifiers
• string`${x} and ${y}` interpolated strings

[jclark]

Some languages (e.g. XML) allow both " and ' with the same semantics so you can easily include strings that use one of these two characters without bothering about quoting.

[jclark]

Our delimited identifier syntax is ugly, so it's an obvious choice to make use of single quotes. The question is whether delimited identifiers are sufficiently widely used to justify dedicating single quote to them. They are not much used in other languages, but maybe we can use them more:

• if you are using a GUI to create programs, it is much less natural to restrict identifiers as textual programming languages typically do
• XML allows characters in names that Ballerina doesn't (most notably hyphen)
• JSON data formats may also use field names (i.e. property names) that are not Ballerina identifiers
• for resource functions, URL segments might want to allow things that are not Ballerina identifiers

Is that enough? I'm not sure.

[jclark]

In Excel, single quote is used at the beginning of a cell to indicate that something that looks like a number should be treated as text.

[jclark]

So I think the realistic options are:

1. Use single quotes for delimited identifiers
2. Use single quotes for string. Two variations depending on how content of single-quoted string is treated:
   1. Same as double-quoted string (XML, Python, JavaScript)
   2. Different from double-quoted string (perl, sh; escapes are not recognized in single-quotes)

[jclark]

I think 2(i) is the most Mort-friendly, and the most consistent with our "be familiar" design principle. There's a strong C-family expectation that 'X' means character X, and the way we represent characters in Ballerina is by strings of length one; JavaScript is very similar in this respect, and allows single quotes for strings, interpreting them exactly the same as double quotes.

At the same time, I do not like our delimited identifier syntax, and think we should make another effort to find something better.

[jclark]

Another data point: SQL 92 uses double quotes for delimited identifiers.

[jclark]

Could use 'x to mean "x".

[jclark]

Using single quotes for delimited identifiers would cause problems for the unwary:

string s = "!whoops!";
// lots of code here
string x = "person";
x = x + 's';