rfc:ast_based_parsing_compilation_process
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rfc:ast_based_parsing_compilation_process [2012/09/07 14:01] – nikic | rfc:ast_based_parsing_compilation_process [2014/08/18 16:45] – nikic | ||
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* Date: 2012-09-04 | * Date: 2012-09-04 | ||
* Author: Nikita Popov < | * Author: Nikita Popov < | ||
- | * Status: | + | * Status: |
+ | * [[http:// | ||
+ | * Superseded by: [[rfc: | ||
===== Introduction ===== | ===== Introduction ===== | ||
+ | |||
+ | **Note: This RFC has been superseded by another [[rfc: | ||
Currently PHP uses a single-pass compilation process, i.e. the parser directly invokes opcode compilation routines. Most other languages on the other hand use an intermediary structure to separate those two phases: The parser only emits an abstract syntax tree (AST), which is then used by a separate compiler to emit instructions. The use of an AST decouples the two phases and as such allows for greater flexibility and deeper analysis. | Currently PHP uses a single-pass compilation process, i.e. the parser directly invokes opcode compilation routines. Most other languages on the other hand use an intermediary structure to separate those two phases: The parser only emits an abstract syntax tree (AST), which is then used by a separate compiler to emit instructions. The use of an AST decouples the two phases and as such allows for greater flexibility and deeper analysis. | ||
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With the current single-pass compiler some things are very hard / near impossible to implement. This actively influences syntax decisions. | With the current single-pass compiler some things are very hard / near impossible to implement. This actively influences syntax decisions. | ||
- | Two examples of syntax that is currently not possible, but would be possible with a syntax tree: | + | A few examples of syntax that is currently not possible, but would be possible with a syntax tree: |
* Array destructuring using something like '' | * Array destructuring using something like '' | ||
* List comprehensions / generator expressions where the result expression comes first, e.g. '' | * List comprehensions / generator expressions where the result expression comes first, e.g. '' | ||
+ | * C#-style expression trees (which form the basis for LINQ) | ||
Apart from larger syntax limitations the current system commonly also affects smaller syntax decisions. One example here are the strange parentheses requirements for the '' | Apart from larger syntax limitations the current system commonly also affects smaller syntax decisions. One example here are the strange parentheses requirements for the '' |
rfc/ast_based_parsing_compilation_process.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1