/**
 * Returns a formatted string:
 *
 *     string sprintf(string format, mixed arg1?, mixed arg2?, ...)
 *
 * ### Argument swapping
 *
 * You can also swap the arguments. That is, the order of the placeholders doesn't have to match the order of the arguments.
 * You can do that by simply indicating in the format string which arguments the placeholders refer to:
 *
 *     sprintf('%2$s %3$s a %1$s', 'cracker', 'Polly', 'wants')
 *
 * And, of course, you can repeat the placeholders without having to increase the number of arguments.
 *
 * ### Named arguments
 *
 * Format strings may contain replacement fields rather than positional placeholders. Instead of referring to a certain argument,
 * you can now refer to a certain key within an object. Replacement fields are surrounded by rounded parentheses - `(` and `)` -
 * and begin with a keyword that refers to a key:
 *
 *     var user = {
 *         name: 'Dolly',
 *     }
 *     sprintf('Hello %(name)s', user) // Hello Dolly
 *
 * Keywords in replacement fields can be optionally followed by any number of keywords or indexes:
 *
 *     var users = [
 *         {name: 'Dolly'},
 *         {name: 'Molly'},
 *         {name: 'Polly'},
 *     ]
 *     sprintf('Hello %(users[0].name)s, %(users[1].name)s and %(users[2].name)s', {users: users}) // Hello Dolly, Molly and Polly
 *
 * Note: mixing positional and named placeholders is not (yet) supported
 *
 * ### Computed values
 *
 * You can pass in a function as a dynamic value and it will be invoked (with no arguments) in order to compute the value on the fly.
 *
 *     sprintf('Current date and time: %s', function() { return new Date().toString() })
 *
 * @param format: format string
 * The placeholders in the format string are marked by `%` and are followed by one or more of these elements, in this order:
 * * An optional number followed by a `$` sign that selects which argument index to use for the value. If not specified,
 *   arguments will be placed in the same order as the placeholders in the input string.
 * * An optional `+` sign that forces to preceed the result with a plus or minus sign on numeric values. By default,
 *   only the `-` sign is used on negative numbers.
 * * An optional padding specifier that says what character to use for padding (if specified). Possible values are
 *   `0` or any other character precedeed by a `'` (single quote). The default is to pad with *spaces*.
 * * An optional `-` sign, that causes `sprintf` to left-align the result of this placeholder. The default is to right-align the result.
 * * An optional number, that says how many characters the result should have. If the value to be returned is shorter
 *   than this number, the result will be padded. When used with the `j` (JSON) type specifier, the padding length
 *   specifies the tab size used for indentation.
 * * An optional precision modifier, consisting of a `.` (dot) followed by a number, that says how many digits should be
 *   displayed for floating point numbers. When used with the `g` type specifier, it specifies the number of significant
 *   digits. When used on a string, it causes the result to be truncated.
 * * A type specifier that can be any of:
 *     * `%` — yields a literal `%` character
 *     * `b` — yields an integer as a binary number
 *     * `c` — yields an integer as the character with that ASCII value
 *     * `d` or `i` — yields an integer as a signed decimal number
 *     * `e` — yields a float using scientific notation
 *     * `u` — yields an integer as an unsigned decimal number
 *     * `f` — yields a float as is; see notes on precision above
 *     * `g` — yields a float as is; see notes on precision above
 *     * `o` — yields an integer as an octal number
 *     * `s` — yields a string as is
 *     * `t` — yields `true` or `false`
 *     * `T` — yields the type of the argument<sup><a href="#fn-1" name="fn-ref-1">1</a></sup>
 *     * `v` — yields the primitive value of the specified argument
 *     * `x` — yields an integer as a hexadecimal number (lower-case)
 *     * `X` — yields an integer as a hexadecimal number (upper-case)
 *     * `j` — yields a JavaScript object or array as a JSON encoded string
 * @param args: the arguments for the format string
 */
export function sprintf(format: string, ...args: any[]): string;

/**
 * Same as `sprintf` except it takes an array of arguments, rather than a variable number of arguments:
 *
 *     string vsprintf(string format, array arguments?)
 *
 * ### Argument swapping
 *
 * You can also swap the arguments. That is, the order of the placeholders doesn't have to match the order of the arguments.
 * You can do that by simply indicating in the format string which arguments the placeholders refer to:
 *
 *     sprintf('%2$s %3$s a %1$s', 'cracker', 'Polly', 'wants')
 *
 * And, of course, you can repeat the placeholders without having to increase the number of arguments.
 *
 * ### Named arguments
 *
 * Format strings may contain replacement fields rather than positional placeholders. Instead of referring to a certain argument,
 * you can now refer to a certain key within an object. Replacement fields are surrounded by rounded parentheses - `(` and `)` -
 * and begin with a keyword that refers to a key:
 *
 *     var user = {
 *         name: 'Dolly',
 *     }
 *     sprintf('Hello %(name)s', user) // Hello Dolly
 *
 * Keywords in replacement fields can be optionally followed by any number of keywords or indexes:
 *
 *     var users = [
 *         {name: 'Dolly'},
 *         {name: 'Molly'},
 *         {name: 'Polly'},
 *     ]
 *     sprintf('Hello %(users[0].name)s, %(users[1].name)s and %(users[2].name)s', {users: users}) // Hello Dolly, Molly and Polly
 *
 * Note: mixing positional and named placeholders is not (yet) supported
 *
 * ### Computed values
 *
 * You can pass in a function as a dynamic value and it will be invoked (with no arguments) in order to compute the value on the fly.
 *
 *     sprintf('Current date and time: %s', function() { return new Date().toString() })
 *
 * @param format: format string
 *
 * The placeholders in the format string are marked by `%` and are followed by one or more of these elements, in this order:
 *
 * * An optional number followed by a `$` sign that selects which argument index to use for the value. If not specified,
 *   arguments will be placed in the same order as the placeholders in the input string.
 * * An optional `+` sign that forces to preceed the result with a plus or minus sign on numeric values. By default,
 *   only the `-` sign is used on negative numbers.
 * * An optional padding specifier that says what character to use for padding (if specified). Possible values are
 *   `0` or any other character precedeed by a `'` (single quote). The default is to pad with *spaces*.
 * * An optional `-` sign, that causes `sprintf` to left-align the result of this placeholder. The default is to right-align the result.
 * * An optional number, that says how many characters the result should have. If the value to be returned is shorter
 *   than this number, the result will be padded. When used with the `j` (JSON) type specifier, the padding length
 *   specifies the tab size used for indentation.
 * * An optional precision modifier, consisting of a `.` (dot) followed by a number, that says how many digits should be
 *   displayed for floating point numbers. When used with the `g` type specifier, it specifies the number of significant
 *   digits. When used on a string, it causes the result to be truncated.
 * * A type specifier that can be any of:
 *     * `%` — yields a literal `%` character
 *     * `b` — yields an integer as a binary number
 *     * `c` — yields an integer as the character with that ASCII value
 *     * `d` or `i` — yields an integer as a signed decimal number
 *     * `e` — yields a float using scientific notation
 *     * `u` — yields an integer as an unsigned decimal number
 *     * `f` — yields a float as is; see notes on precision above
 *     * `g` — yields a float as is; see notes on precision above
 *     * `o` — yields an integer as an octal number
 *     * `s` — yields a string as is
 *     * `t` — yields `true` or `false`
 *     * `T` — yields the type of the argument<sup><a href="#fn-1" name="fn-ref-1">1</a></sup>
 *     * `v` — yields the primitive value of the specified argument
 *     * `x` — yields an integer as a hexadecimal number (lower-case)
 *     * `X` — yields an integer as a hexadecimal number (upper-case)
 *     * `j` — yields a JavaScript object or array as a JSON encoded string
 * @param args: the arguments for the format string
 */
export function vsprintf(format: string, args: any[]): string;