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Cleanup syntax doc
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Victor Zverovich
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doc/syntax.md
128
doc/syntax.md
@ -5,8 +5,8 @@ same format string syntax described in this section.
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Format strings contain "replacement fields" surrounded by curly braces `{}`.
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Anything that is not contained in braces is considered literal text, which is
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copied unchanged to the output. If you need to include a brace character in the
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literal text, it can be escaped by doubling: `{{` and `}}`.
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copied unchanged to the output. If you need to include a brace character in
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the literal text, it can be escaped by doubling: `{{` and `}}`.
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The grammar for a replacement field is as follows:
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@ -31,9 +31,9 @@ non-default format for the replacement value.
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See also the [Format Specification
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Mini-Language](#format-specification-mini-language) section.
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If the numerical arg_ids in a format string are 0, 1, 2, ... in
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sequence, they can all be omitted (not just some) and the numbers 0, 1,
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2, ... will be automatically inserted in that order.
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If the numerical arg_ids in a format string are 0, 1, 2, ... in sequence,
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they can all be omitted (not just some) and the numbers 0, 1, 2, ... will be
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automatically inserted in that order.
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Named arguments can be referred to by their names or indices.
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@ -123,8 +123,8 @@ Note that unless a minimum field width is defined, the field width will
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always be the same size as the data to fill it, so that the alignment
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option has no meaning in this case.
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The *sign* option is only valid for floating point and signed integer
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types, and can be one of the following:
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The *sign* option is only valid for floating point and signed integer types,
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and can be one of the following:
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<table>
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<tr>
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@ -188,27 +188,57 @@ characters will be used from the field content. The *precision* is not
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allowed for integer, character, Boolean, and pointer values. Note that a
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C string must be null-terminated even if precision is specified.
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The `'L'` option uses the current locale setting to insert the
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appropriate number separator characters. This option is only valid for
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numeric types.
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The `'L'` option uses the current locale setting to insert the appropriate
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number separator characters. This option is only valid for numeric types.
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Finally, the *type* determines how the data should be presented.
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The available string presentation types are:
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| Type | Meaning |
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|-------|-------------------------------------------------------------------------|
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| `'s'` | String format. This is the default type for strings and may be omitted. |
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| `'?'` | Debug format. The string is quoted and special characters escaped. |
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| none | The same as `'s'`. |
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<table>
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<tr>
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<th>Type</th>
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<th>Meaning</th>
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</tr>
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<tr>
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<td><code>'s'</code></td>
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<td>
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String format. This is the default type for strings and may be omitted.
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</td>
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</tr>
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<tr>
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<td><code>'?'</code></td>
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<td>Debug format. The string is quoted and special characters escaped.</td>
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</tr>
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<tr>
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<td>none</td>
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<td>The same as <code>'s'</code>.</td>
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</tr>
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</table>
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The available character presentation types are:
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| Type | Meaning |
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|-------|-------------------------------------------------------------------------------|
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| `'c'` | Character format. This is the default type for characters and may be omitted. |
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| `'?'` | Debug format. The character is quoted and special characters escaped. |
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| none | The same as `'c'`. |
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<table>
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<tr>
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<th>Type</th>
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<th>Meaning</th>
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</tr>
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<tr>
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<td><code>'c'</code></td>
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<td>
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Character format. This is the default type for characters and may be
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omitted.
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</td>
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</tr>
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<tr>
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<td><code>'?'</code></td>
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<td>Debug format. The character is quoted and special characters escaped.</td>
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</tr>
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<tr>
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<td>none</td>
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<td>The same as <code>'c'</code>.</td>
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</tr>
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</table>
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The available integer presentation types are:
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@ -347,35 +377,48 @@ The available presentation types for floating-point values are:
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The available presentation types for pointers are:
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| Type | Meaning |
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|-------|---------------------------------------------------------------------------|
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| `'p'` | Pointer format. This is the default type for pointers and may be omitted. |
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| none | The same as `'p'`. |
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<table>
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<tr>
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<th>Type</th>
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<th>Meaning</th>
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</tr>
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<tr>
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<td><code>'p'</code></td>
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<td>
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Pointer format. This is the default type for pointers and may be omitted.
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</td>
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</tr>
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<tr>
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<td>none</td>
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<td>The same as <code>'p'</code>.</td>
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</tr>
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</table>
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## Chrono Format Specifications
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Format specifications for chrono duration and time point types as well
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as `std::tm` have the following syntax:
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Format specifications for chrono duration and time point types as well as
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`std::tm` have the following syntax:
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<a id="chrono-format-spec"></a>
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<pre>
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chrono_format_spec ::= [[<a href="#format-spec">fill</a>]<a href="#format-spec"
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>align</a>][<a href="#format-spec">width</a>]["." <a href="#format-spec"
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>precision</a>][chrono_specs]
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chrono_specs ::= [chrono_specs] conversion_spec | chrono_specs literal_char
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chrono_specs ::= conversion_spec | <!--
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-->chrono_specs (conversion_spec | literal_char)
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conversion_spec ::= "%" [padding_modifier] [locale_modifier] chrono_type
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literal_char ::= <a character other than '{', '}' or '%'>
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padding_modifier ::= "-" | "_" | "0"
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locale_modifier ::= "E" | "O"
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chrono_type ::= "a" | "A" | "b" | "B" | "c" | "C" | "d" | "D" | "e" | "F" |
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"g" | "G" | "h" | "H" | "I" | "j" | "m" | "M" | "n" | "p" |
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"q" | "Q" | "r" | "R" | "S" | "t" | "T" | "u" | "U" | "V" |
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"w" | "W" | "x" | "X" | "y" | "Y" | "z" | "Z" | "%"
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chrono_type ::= "a" | "A" | "b" | "B" | "c" | "C" | "d" | "D" | "e" |
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"F" | "g" | "G" | "h" | "H" | "I" | "j" | "m" | "M" |
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"n" | "p" | "q" | "Q" | "r" | "R" | "S" | "t" | "T" |
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"u" | "U" | "V" | "w" | "W" | "x" | "X" | "y" | "Y" |
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"z" | "Z" | "%"
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</pre>
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Literal chars are copied unchanged to the output. Precision is valid
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only for `std::chrono::duration` types with a floating-point
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representation type.
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Literal chars are copied unchanged to the output. Precision is valid only
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for `std::chrono::duration` types with a floating-point representation type.
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The available presentation types (*chrono_type*) are:
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@ -507,9 +550,9 @@ The available presentation types (*chrono_type*) are:
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<tr>
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<td><code>'M'</code></td>
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<td>
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The minute as a decimal number. If the result is a single digit, it is
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prefixed with 0. The modified command <code>%OM</code> produces the locale's
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alternative representation.
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The minute as a decimal number. If the result is a single digit, it
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is prefixed with 0. The modified command <code>%OM</code> produces the
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locale's alternative representation.
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</td>
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</tr>
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<tr>
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@ -657,8 +700,8 @@ The available presentation types (*chrono_type*) are:
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</tr>
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</table>
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Specifiers that have a calendaric component such as `'d'` (the day of
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month) are valid only for `std::tm` and time points but not durations.
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Specifiers that have a calendaric component such as `'d'` (the day of month)
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are valid only for `std::tm` and time points but not durations.
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The available padding modifiers (*padding_modifier*) are:
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@ -668,8 +711,8 @@ The available padding modifiers (*padding_modifier*) are:
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| `'_'` | Do not pad a numeric result string. |
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| `'0'` | Pad a numeric result string with zeros. |
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Currently, these modifiers are only supported for the `'H'`, `'I'`, `'M'`,
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`'S'`, `'U'`, `'V'` and `'W'` presentation types.
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These modifiers are only supported for the `'H'`, `'I'`, `'M'`, `'S'`, `'U'`,
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`'V'` and `'W'` presentation types.
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## Range Format Specifications
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@ -679,8 +722,7 @@ Format specifications for range types have the following syntax:
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range_format_spec ::= ["n"][range_type][range_underlying_spec]
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</pre>
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The `'n'` option formats the range without the opening and closing
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brackets.
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The `'n'` option formats the range without the opening and closing brackets.
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The available presentation types for `range_type` are:
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