1[/ 2 Copyright 2006-2007 John Maddock. 3 Distributed under the Boost Software License, Version 1.0. 4 (See accompanying file LICENSE_1_0.txt or copy at 5 http://www.boost.org/LICENSE_1_0.txt). 6] 7 8 9[section:boost_format_syntax Boost-Extended Format String Syntax] 10 11Boost-Extended format strings treat all characters as literals except for 12'$', '\\', '(', ')', '?', and ':'. 13 14[h4 Grouping] 15 16The characters '(' and ')' perform lexical grouping, so use \\( and \\) if you 17want a to output literal parenthesis. 18 19[h4 Conditionals] 20 21The character '?' begins a conditional expression, the general form is: 22 23?Ntrue-expression:false-expression 24 25where N is decimal digit. 26 27If sub-expression N was matched, then true-expression is evaluated and sent to 28output, otherwise false-expression is evaluated and sent to output. 29 30You will normally need to surround a conditional-expression with parenthesis in 31order to prevent ambiguities. 32 33For example, the format string "(?1foo:bar)" will replace each match found with "foo" if 34the sub-expression $1 was matched, and with "bar" otherwise. 35 36For sub-expressions with an index greater than 9, or for access to named sub-expressions use: 37 38?{INDEX}true-expression:false-expression 39 40or 41 42?{NAME}true-expression:false-expression 43 44 45[h4 Placeholder Sequences] 46 47Placeholder sequences specify that some part of what matched the regular expression 48should be sent to output as follows: 49 50[table 51[[Placeholder][Meaning]] 52[[$&][Outputs what matched the whole expression.]] 53[[$MATCH][As $&]] 54[[${^MATCH}][As $&]] 55[[$\`][Outputs the text between the end of the last match found (or the 56 start of the text if no previous match was found), and the start 57 of the current match.]] 58[[$PREMATCH][As $\`]] 59[[${^PREMATCH}][As $\`]] 60[[$'][Outputs all the text following the end of the current match.]] 61[[$POSTMATCH][As $']] 62[[${^POSTMATCH}][As $']] 63[[$+][Outputs what matched the last marked sub-expression in the regular expression.]] 64[[$LAST_PAREN_MATCH][As $+]] 65[[$LAST_SUBMATCH_RESULT][Outputs what matched the last sub-expression to be actually matched.]] 66[[$^N][As $LAST_SUBMATCH_RESULT]] 67[[$$][Outputs a literal '$']] 68[[$n][Outputs what matched the n'th sub-expression.]] 69[[${n}][Outputs what matched the n'th sub-expression.]] 70[[$+{NAME}][Outputs whatever matched the sub-expression named "NAME".]] 71] 72 73Any $-placeholder sequence not listed above, results in '$' being treated as a literal. 74 75[h4 Escape Sequences] 76 77An escape character followed by any character x, outputs that character unless 78x is one of the escape sequences shown below. 79 80[table 81[[Escape][Meaning]] 82[[\\a][Outputs the bell character: '\\a'.]] 83[[\\e][Outputs the ANSI escape character (code point 27).]] 84[[\\f][Outputs a form feed character: '\\f']] 85[[\\n][Outputs a newline character: '\\n'.]] 86[[\\r][Outputs a carriage return character: '\\r'.]] 87[[\\t][Outputs a tab character: '\\t'.]] 88[[\\v][Outputs a vertical tab character: '\\v'.]] 89[[\\xDD][Outputs the character whose hexadecimal code point is 0xDD]] 90[[\\x{DDDD}][Outputs the character whose hexadecimal code point is 0xDDDDD]] 91[[\\cX][Outputs the ANSI escape sequence "escape-X".]] 92[[\\D][If D is a decimal digit in the range 1-9, then outputs the text that matched sub-expression D.]] 93[[\\l][Causes the next character to be outputted, to be output in lower case.]] 94[[\\u][Causes the next character to be outputted, to be output in upper case.]] 95[[\\L][Causes all subsequent characters to be output in lower case, until a \\E is found.]] 96[[\\U][Causes all subsequent characters to be output in upper case, until a \\E is found.]] 97[[\\E][Terminates a \\L or \\U sequence.]] 98] 99 100[endsect] 101 102 103