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Function std.format.format

Converts its arguments according to a format string into a string.

immutable(Char)[] format(Char, Args...) (
  in Char[] fmt,
  Args args
if (isSomeChar!Char);

typeof(fmt) format(alias fmt, Args...) (
  Args args
if (isSomeString!(typeof(fmt)));

The second version of format takes the format string as template argument. In this case, it is checked for consistency at compile-time and produces slightly faster code, because the length of the output buffer can be estimated in advance.


fmt a format string
args a variadic list of arguments to be formatted
Char character type of fmt
Args a variadic list of types of the arguments


The formatted string.


A FormatException if formatting did not succeed.

See Also

sformat for a variant, that tries to avoid garbage collection.


writeln(format("Here are %d %s.", 3, "apples")); // "Here are 3 apples."

writeln("Increase: %7.2f %%".format(17.4285)); // "Increase:   17.43 %"


The format string can be checked at compile-time:

auto s = format!"%s is %s"("Pi", 3.14);
writeln(s); // "Pi is 3.14"

// This line doesn't compile, because 3.14 cannot be formatted with %d:
// s = format!"%s is %d"("Pi", 3.14);


Walter Bright, Andrei Alexandrescu, and Kenji Hara


Boost License 1.0.