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The simple Sethi–Ullman algorithm works as follows (for a load/store architecture): . Traverse the abstract syntax tree in pre- or postorder . For every leaf node, if it is a non-constant left-child, assign a 1 (i.e. 1 register is needed to hold the variable/field/etc.), otherwise assign a 0 (it is a non-constant right child or constant leaf node (RHS of an operation – literals, values)).
An abstract syntax tree (AST) is a data structure used in computer science to represent the structure of a program or code snippet. It is a tree representation of the abstract syntactic structure of text (often source code) written in a formal language. Each node of the tree denotes a construct occurring in the text.
A counterpart of a UD Chain is a definition-use chain (or DU chain), which consists of a definition D of a variable and all the uses U reachable from that definition without any other intervening definitions. [3] Both UD and DU chains are created by using a form of static code analysis known as data flow analysis.
The following example shows how to use Bison and flex to write a simple calculator program (only addition and multiplication) and a program for creating an abstract syntax tree. The next two files provide definition and implementation of the syntax tree functions.
An intermediate language is the language of an abstract machine designed to aid in the analysis of computer programs.The term comes from their use in compilers, where the source code of a program is translated into a form more suitable for code-improving transformations before being used to generate object or machine code for a target machine.
In computer science, a symbol table is a data structure used by a language translator such as a compiler or interpreter, where each identifier, symbol, constant, procedure and function in a program's source code is associated with information relating to its declaration or appearance in the source. In other words, the entries of a symbol table ...
The original Lunar Lander makes an excellent example for examining FOCAL code, as it uses most of the features of the language. This code is from the original, found on Jim Storer's Lunar Lander page. [31] 01.04 T "CONTROL CALLING LUNAR MODULE. MANUAL CONTROL IS NECESSARY"! 01.06 T "YOU MAY RESET FUEL RATE K EACH 10 SECS TO 0 OR ANY VALUE"!
Tree-sitter parsers have been written for these languages and many others. [11] GitHub uses Tree-sitter to support in-browser symbolic code navigation in Git repositories. [12] Tree-sitter uses a GLR parser, a type of LR parser. [13] [14] [12] Tree-sitter was originally developed by GitHub for use in the Atom text editor, where it was first ...