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<div class="moz-cite-prefix">On 14/03/2024 19:39, Guy Steele wrote:<br>
</div>
<blockquote type="cite" cite="mid:F217B131-C5FD-4587-B251-06760F08DD36@oracle.com">
This is a very important example to consider. I observe, however,
that there are at least two possible ways to avoid the unpleasant
surprise:
<div><br>
</div>
<div>(1) Don't have string interpolation literals, because
accidentally using a string interpolation literal instead of a
string template literals can result in invoking the wrong
overload of a method.</div>
<div>
<div><br>
</div>
<div>(2) Don’t overload methods so as to accept either a string
or a string template.</div>
</div>
</blockquote>
<p>I agree with your analysis, but note that there is also a third
option:</p>
<p>(3) make it so that both string interpolation literal and string
template literal have a prefix.</p>
<p>I believe that is enough to solve the issue (because the program
I wrote would no longer compile: the compiler would require an
explicit prefix).<br>
</p>
<p>Maurizio<br>
</p>
<blockquote type="cite" cite="mid:F217B131-C5FD-4587-B251-06760F08DD36@oracle.com">
<div>
<div><br>
</div>
<div>If we were to take approach (2), then:</div>
<div><br>
</div>
<div>(a) We would keep `println` as is, and not allow it to
accept a template, but that’s okay—if you thought you wanted a
template, what you really want is plan old string
interpolation, and the type checking will make sure you don't
use the wrong one.</div>
<div><br>
</div>
<div>
<div>(b) A SQL processor would accept a template but not a
string—if you thought you wanted string interpolation, what
you really want is a template, and the type checking will
make sure you don't use the wrong one.</div>
<div><br>
</div>
<div>(c) I think `format` is a special case that we tend to
get hung up on, and I think that, in this particular branch
of the design space we are exploring, perhaps a name other
than `String.format` should be chosen for the method that
does string formatting on templates. Possible names are
`StringTemplate.format` and `String.format$`, but I will
leave further bikeshedding on this to others. I do recognize
that this move will not enable the type system per se to
absolutely prevent programmers from writing</div>
<div class="markdown-here-wrapper" data-md-url="">
<pre style="font-family: Consolas, Inconsolata, Courier, monospace; font-size: 1em; line-height: 1.2em; margin-top: 1.2em; margin-bottom: 1.2em;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace; margin: 0px 0.15em; background-color: rgb(248, 248, 248); overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;">String.format("Hello, my name is %s{name}"); // can you spot the bug?
</code></pre>
</div>
<div>but, as Clement has observed, such cases will probably
provoke a warning about a mismatch between the number of
arguments and the number of %-specifiers that require
parameters, so maybe overloading would be okay anyway for
`String.format`.</div>
</div>
<div><br>
</div>
<div>Anyway, my point is that whether to overload a method to
accept either a string or a string template can be evaluated
on a case-by-case basis according to a small number of
principles that I think we could enumerate and explain pretty
easily.</div>
<div><br>
</div>
<div>—Guy</div>
<div>
<div><br>
<blockquote type="cite">
<div>On Mar 14, 2024, at 1:40 PM, Maurizio Cimadamore
<a class="moz-txt-link-rfc2396E" href="mailto:maurizio.cimadamore@oracle.com"><maurizio.cimadamore@oracle.com></a> wrote:</div>
<br class="Apple-interchange-newline">
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<div>
<div class="markdown-here-wrapper" data-md-url="" style="">
<p style="margin: 0px 0px 1.2em !important;">Not to
pour too much cold water on the idea of having
string interpolation literal, but I’d like to
mention a few points here.</p>
<p style="margin: 0px 0px 1.2em !important;">First,
it was a deliberate design goal of the string
template feature to make interpolation an explicit
act. Note that, if we had the syntax you describe,
we actually achieve the opposite effect: string
interpolation is now the default, and implicit,
and actually <em>cheaper</em> (to type) than the
safer template alternative. This is a bit of a red
herring, I think.</p>
<p style="margin: 0px 0px 1.2em !important;">The
second problem is that interpolation literals can
sometimes be deceiving. Consider this example:</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;">String.format("Hello, my name is %s{name}"); // can you spot the bug?
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">Where <code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;">
String::format</code> has a new overload which accepts a StringTemplate.</p>
<p style="margin: 0px 0px 1.2em !important;">Basically,
since here we forgot the leading “$” (or whatever
char that is), the whole thing is just a big
interpolation. Semantically equivalent to:</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;"> String.format("Hello, my name is %s" + name); // whoops!
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">This
will fail, as <code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;">
String::format</code> will be waiting for an argument (a string), but
none is provided. So:</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;">| Exception java.util.MissingFormatArgumentException: Format specifier '%s'
| at Formatter.format (Formatter.java:2672)
| at Formatter.format (Formatter.java:2609)
| at String.format (String.java:2897)
| at (#2:1)
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">This is
a very odd (and new!) failure mode, that I’m sure
is gonna surprise developers.</p>
<p style="margin: 0px 0px 1.2em !important;">Maurizio</p>
<p style="margin: 0px 0px 1.2em !important;">On
14/03/2024 15:08, Guy Steele wrote:</p>
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<blockquote type="cite" cite="mid:3F8C64A7-BEB8-4BA2-A9B1-E00C14578B28@oracle.com">
<pre class="moz-quote-pre" wrap="">Second thoughts about how to explain a string interpolation literal:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On Mar 13, 2024, at 2:02 PM, Guy Steele <a class="moz-txt-link-rfc2396E" href="mailto:guy.steele@oracle.com" moz-do-not-send="true"><guy.steele@oracle.com></a> wrote:
. . .
—————————
String is not a subtype of StringTemplate; they are disjoint types.
$”foo” is a (trivial) string template literal
“foo” is a string literal
$”Hello, \{x}” is a (nontrivial) string template literal
“Hello, \{x}” is a shorthand (expanded by the compiler) for `String.of($“Hello, \{x}”)`
—————————
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">Given that the intent is that String.of (or whatever we want to call it—possibly the `interpolation` instance method of class `StringTemplate` rather than a static method `String.of`) should just do standard string concatenation, we might be better off just saying that a string interpolation literal is expanded by the compiler into uses of “+”; for example,
“Hello, \{x}.”
(I have added a period to the example to make the point clearer) is expanded into
“Hello, “ + x + “.”
and in general
“c0\{e1}c1\{e2}c2…\{en}cn”
(where each ck is a possibly empty sequence of string characters and each ek is an expression) is expanded into
“c0” + (e1) + “c1” + (e2) + “c2” + … + (en) + “cn”
The point is that, with this definition, “c0\{e1}c1\{e2}c2…\{en}cn” is a constant expression iff every ek is a constant expression. This is handy for interpolating constant variables into a string that is itself intended to be constant.
—Guy
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