Boost-Extended Format String Syntax
To increase string-search flexibility, Boost-Extended format strings treat the majority of characters as literals. These are the only exceptions: $ ( ) , \ : ?
.
Boost-Extended format strings interpret those characters literally so that you can use them for common functions that require you to format strings. To interpret any of those characters as literals, you must precede them with a \.
Go to Boost-Extended Format String Syntax for more information about these:
Grouping
Conditionals
Placeholder Sequences
Escape Sequences