Bug 13480 – Input range formatting should not format as "elements"

Consider the following (output in comments): --- import std.algorithm; import std.stdio; import std.string; void main() { auto ror = ["one", "two", "three"]; writefln("%(%s%| %)", [1, 2, 3]); // 1 2 3 writefln("%(%s%| %)", "abc"); // 'a' 'b' 'c' writefln("%(%s%|, %)", ror); // "one", "two", "three" writefln("%s", ror.joiner(", ")); // one, two, three writefln("%s", ror); // ["one", "two", "three"] } --- writefln statement #2 and #3 don't make any sense. Formatting characters and strings using the element markup style (`formatElement`), which forces single and double quotes around the character or string respectively, defeats the purpose of range-based formatting, which allows you to customize the fluff around each element. Not adding quotes is the more general solution; when quotes are desired, they can be explicitly added like so: `%("%s"%|, %)`. This behaviour neuters range-based formatting severely: std.format deals with creating text, and strings and characters are the most basic units of text, yet this behaviour renders range-based formatting unusable when quotes are not desired (which is probably the vast majority of cases).

(In reply to Jakob Ovrum from comment #0) > writefln statement #2 and #3 don't make any sense. Formatting characters and > strings using the element markup style (`formatElement`), which forces > single and double quotes around the character or string respectively, > defeats the purpose of range-based formatting, which allows you to customize > the fluff around each element. If you want to stop automatic element quoting, you can use "%-(". void main() { auto ror = ["one", "two", "three"]; writefln("%-(%s%| %)", [1, 2, 3]); // 1 2 3 writefln("%-(%s%| %)", "abc"); // a b c writefln("%-(%s%|, %)", ror); // one, two, three } It's documented in: http://dlang.org/phobos/std_format > Inside a compound format specifier, strings and characters are escaped > automatically. To avoid this behavior, add '-' flag to "%(".

(In reply to Kenji Hara from comment #1) > If you want to stop automatic element quoting, you can use "%-(". > > void main() > { > auto ror = ["one", "two", "three"]; > writefln("%-(%s%| %)", [1, 2, 3]); // 1 2 3 > writefln("%-(%s%| %)", "abc"); // a b c > writefln("%-(%s%|, %)", ror); // one, two, three > } > > It's documented in: http://dlang.org/phobos/std_format > > > Inside a compound format specifier, strings and characters are escaped > > automatically. To avoid this behavior, add '-' flag to "%(". Thanks, nice to know it's possible to work around. However, I don't think this flag should need to exist. If strings were simply not quoted, one could get quoting by doing the much more intuitive explicit quoting: `%("%s"%|, %)`. Using '-' is just a hack - it has nothing to do with left-justification and thus the reader has to look it up to know what it does. We should follow the principle of least surprise here, by formatting the string as-is unless quoting is added by the user. (changed severity to enhancement)

(In reply to Jakob Ovrum from comment #2) > Thanks, nice to know it's possible to work around. > > However, I don't think this flag should need to exist. > > If strings were simply not quoted, one could get quoting by doing the much > more intuitive explicit quoting: `%("%s"%|, %)`. Using '-' is just a hack - > it has nothing to do with left-justification and thus the reader has to look > it up to know what it does. We should follow the principle of least surprise > here, by formatting the string as-is unless quoting is added by the user. Handmade quoting is not enough for strings which contain double-quote character. See: import std.stdio; void main() { string s = `Hello "D" world!`; writefln("[%(%s%)]", [s]); } will output: ["Hello \"D\" world!"] By design, std.format.formatValue functions stringize values by using unformattable representation with unformatValue functions by default. That's the reason why automatic quoting is done by default.

(In reply to Kenji Hara from comment #3) > (In reply to Jakob Ovrum from comment #2) > > Thanks, nice to know it's possible to work around. > > > > However, I don't think this flag should need to exist. > > > > If strings were simply not quoted, one could get quoting by doing the much > > more intuitive explicit quoting: `%("%s"%|, %)`. Using '-' is just a hack - > > it has nothing to do with left-justification and thus the reader has to look > > it up to know what it does. We should follow the principle of least surprise > > here, by formatting the string as-is unless quoting is added by the user. > > Handmade quoting is not enough for strings which contain double-quote > character. > See: > > import std.stdio; > void main() { > string s = `Hello "D" world!`; > writefln("[%(%s%)]", [s]); > } > > will output: > ["Hello \"D\" world!"] > > By design, std.format.formatValue functions stringize values by using > unformattable representation with unformatValue functions by default. > That's the reason why automatic quoting is done by default. OK, good point. Thanks for explaining!