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I found out that {:?} prints an entire array in Rust. I want to know what is it called and how exactly it works. Is it only limited to printing arrays or could it also be used elsewhere for other purposes?
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String formatting uses a process of string interpolation (variable substitution) to evaluate a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values.
Macro std::formatCreates a String using interpolation of runtime expressions. The first argument format! receives is a format string. This must be a string literal. The power of the formatting string is in the {} s contained.
Short answer: no, not that type of interpolation. There is a Rust RFC for this.
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3), and is typically associated with the corrosion of refined iron.
This is explained (along with the rest of the formatting syntax) in the std::fmt documentation.
{...} surrounds all formatting directives. : separates the name or ordinal of the thing being formatted (which in this case is omitted, and thus means "the next thing") from the formatting options. The ? is a formatting option that triggers the use of the std::fmt::Debug implementation of the thing being formatted, as opposed to the default Display trait, or one of the other traits (like UpperHex or Octal).
Thus, {:?} formats the "next" value passed to a formatting macro, and supports anything that implements Debug.
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