| ragel-guide.txt (ragel-7.0.0.9) | : | ragel-guide.txt (ragel-7.0.0.10) |
|---|
| = Ragel State Machine Compiler User Guide | | = Ragel State Machine Compiler User Guide |
| Adrian Thurston <thurston@colm.net> | | Adrian Thurston <thurston@colm.net> |
| Ragel Version 7.0 | | Ragel Version 7.0 |
| :toc: | | :toc: |
| :toclevels: 3 | | :toclevels: 3 |
| :numbered: | | :numbered: |
| | |
| .License | | .License |
| | |
|
| This document is part of Ragel, and as such, this document is released | | Permission is hereby granted, free of charge, to any person obtaining a c |
| under the terms of the GNU General Public License as published by the | | opy |
| Free Software Foundation; either version 2 of the License, or (at your | | of this software and associated documentation files (the "Software"), to |
| option) any later version. | | deal in the Software without restriction, including without limitation th |
| | e |
| Ragel is distributed in the hope that it will be useful, but WITHOUT | | rights to use, copy, modify, merge, publish, distribute, sublicense, and/ |
| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | | or |
| FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | | sell copies of the Software, and to permit persons to whom the Software i |
| for more details. | | s |
| | furnished to do so, subject to the following conditions: |
| You should have received a copy of the GNU General Public License along | | |
| with Ragel; if not, write to the Free Software Foundation, Inc., 59 | | The above copyright notice and this permission notice shall be included i |
| Temple Place, Suite 330, Boston, MA 02111-1307 USA. | | n all |
| | copies or substantial portions of the Software. |
| | |
| | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS O |
| | R |
| | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL T |
| | HE |
| | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING F |
| | ROM, |
| | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| | THE |
| | SOFTWARE. |
| | |
| == Introduction | | == Introduction |
| | |
| === Abstract | | === Abstract |
| | |
| In today's computing landscape, regular expressions are used heavily for the | | In today's computing landscape, regular expressions are used heavily for the |
| purpose of specifying parsers. They are normally treated as black boxes, linked | | purpose of specifying parsers. They are normally treated as black boxes, linked |
| together with program logic. User code is executed in between invocations of | | together with program logic. User code is executed in between invocations of |
| the regular expression engine. To add code before a pattern terminates, the | | the regular expression engine. To add code before a pattern terminates, the |
| programmer is required to break patterns and paste them back together with | | programmer is required to break patterns and paste them back together with |
| | |
| skipping to change at line 3420 | | skipping to change at line 3424 |
|---|
| needs to be able to allocate characters from the alphabet space. Ragel uses | | needs to be able to allocate characters from the alphabet space. Ragel uses |
| these allocated characters to express "character C with condition P true" or "C | | these allocated characters to express "character C with condition P true" or "C |
| with P false." Since internally Ragel uses longs to store characters there is | | with P false." Since internally Ragel uses longs to store characters there is |
| no room left in the alphabet space unless an alphabet type smaller than long is | | no room left in the alphabet space unless an alphabet type smaller than long is |
| used. | | used. |
| | |
| ==== Condition Based Repetition | | ==== Condition Based Repetition |
| | |
| New in ragel 7 is a construct designed to simplify the use of conditions to | | New in ragel 7 is a construct designed to simplify the use of conditions to |
| control repetition. While possible to count properly using condition embedding | | control repetition. While possible to count properly using condition embedding |
|
| operators, there is a corner case that prove difficult. If the zero-width case | | operators, there is a corner case that proves difficult. If the zero-width case |
| is to be accepted properly, some knowledge of what is before and after is | | is to be accepted properly, some knowledge of what is before and after is |
| necessary and tests need to be embedded there. The `:cond()` operator is | | necessary and tests need to be embedded there. The `:cond()` operator is |
| designed to solve this problem, automatically embedding actions such that a | | designed to solve this problem, automatically embedding actions such that a |
| zero count is possible. | | zero count is possible. |
| | |
| -------------- | | -------------- |
| :cond( <expression>, | | :cond( <expression>, |
| <init>, <inc>, <min> [ , <max> ] ): | | <init>, <inc>, <min> [ , <max> ] ): |
| -------------- | | -------------- |
| | |
| | | |
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