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doc:lara [2022/01/15 19:37]
jbispo created 		doc:lara [2022/01/15 21:05] (current)
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-====== LARA Fundamentals ======+====== LARA Framework Documentation ======
  
-The LARA language is JavaScript (plain JavaScript is valid LARA code) extended with custom syntax oriented for source code analysis and transformation.+LARA is a framework written in Java for writing LARA weavers, tools that analyze and transform source code of a given language according to rules written in LARA scripts. 
 +LARA scripts can either be plain JavaScript files with the latest EcmaScript syntax (.js files) or EcmaScript 5 (2009) extended with special constructs (.lara files).
  
-Recently LARA has been moving away from language-specific constructs (e.g., select, apply) in favor of JavaScript-based APIs (e.g., weaver.Query). +LARA Framework is open source and available at [[https://github.com/specs-feup/lara-framework|GitHub]].
-==== Aspects ====+
  
-Aspects are regions of code where LARA syntax can be used, and are similar to functions. They are also the entry point of a LARA script, the first aspect of the script is executed by default.+[Planned Feature] Currently, the starting point of a LARA weaver is always a .lara file, but we are working on support for the entry point to be either a .lara or .js file.
  
-Aspectdef definition+/* [[https://drive.google.com/drive/folders/1pH5XIdSvLP2q3F7ISfiEe9ql6MT5ciVA?usp=sharing|Quickstart]] - Introductory video about using Kadabra, a Java Weaver (46min).  (unfortunately it is in Portuguese...) */
  
-<code lara> +[[doc:lara:intro|LARA Introduction]] - Introduction to LARA scripts.
-// The main aspect is the first declared in the file +
-aspectdef MyFirstAspect +
-   // aspect code +
-end+
  
-aspectdef ASecondAspect // An aspect that can be called in the main aspect +[[doc:lara:tips|General LARA Tips]] - Tips regarding writing and using LARA scripts.
-   // aspect code +
-end +
-</code>+
  
- +[[doc:lara:legacy|Legacy Lara]] - Tips about features that are considered legacy and no longer actively supported (although they might still work).
- +
-==== Aspect Inputs and Outputs ==== +
- +
-Input parameter definition: +
- +
-<code lara> +
-input +
-    funcs, +
-    opt +
-end +
-</code> +
- +
-Input parameter definition with default values: +
- +
-<code lara> +
-input +
-    funcs = ['kernel'], +
-    opt = ['unroll', 'interchange', 'tile'] +
-end +
-</code> +
- +
-Output definition. Output cannot be initialized inside the **output** block: +
- +
-<code lara> +
-output +
-    optFuncs, +
-    code +
-end +
- +
-optFuncs = []; +
-code = ''; +
-</code> +
- +
-==== Calling Aspects ==== +
- +
-Simple aspect call: +
- +
-<code lara> +
-call OptimizeProgram(); +
-</code> +
- +
-Calling an aspect with arguments: +
- +
-<code lara> +
-call OptimizeFunctions(functions, optimizations); +
-</code> +
- +
-Calling an aspect with named arguments: +
- +
-<code lara> +
-call OptimizeFunctions(opt: optimizations, funcs: ['gridIterate']); +
-</code> +
- +
- +
-Calling an aspect and retrieving the outputs: +
- +
-<code lara> +
-// Current syntax +
-var optimizer = call OptimizeFunctions(functions, optimizations); +
- +
-// Previous syntax +
-call optimizer : OptimizeFunctions(functions, optimizations); +
- +
-var changedFuncs = optimizer.optFuncs; +
-var finalCode = optimizer.code; +
-</code> +
- +
-Assigning an aspect call to a variable for later use. Can still use input arguments and outputs as shown before: +
- +
-<code lara> +
-var optimizer = new OptimizeFunctions(functions, optimizations); +
- +
-call optimizer(); // or optimizer.call() +
- +
-var changedFuncs = optimizer.optFuncs; +
-var finalCode = optimizer.code; +
-</code> +
- +
-Aspects can also be called inside Javascript files (.js). You need to build the aspect object and reference the complete path, separated by dollar signs ($):  +
- +
-<code lara> +
-// Calling aspect MeasureEnergy from inside a .js file +
- +
-(new lara$profiling$Energy$EnergyTest()).call(); +
-</code> +
-==== Using LARA Actions ==== +
- +
-Actions are used inside apply statements. There are two default actions, **insert** and **def**. Then, it is possible to use weaver-specific actions, which are called with the **exec** keyword: +
- +
-<code lara> +
-select function{'kernel'} end +
-apply +
-    insert before '/* Creating a clone. */';  // add a comment before the function +
-    def name = 'original_kernel';  // redefine the name of the kernel function +
-    exec clone('cloned_kernel');  // use a MANET-specific action to create a 'kernel' clone named 'cloned_kernel' +
-end +
-</code> +
- +
-When calling an action we can specify any join point in the chain to be the action target: +
- +
-<code lara> +
-select function.loop end +
-apply +
-    $loop.exec tile(8); +
-    $function.insert before '/* This function was transformed. */'; +
-end +
-</code> +
- +
-It is possible to omit the target, the last join point in the chain is used: +
- +
-<code lara> +
-select function.loop end +
-apply +
-    exec unroll(2);  // performed on the same loop as below +
-    $loop.exec tile(8);  // performed on the same loop as above +
-end +
-</code> +
- +
- +
-If the action returns a result, we can use the following syntax: +
- +
-<code lara> +
-   var result = $jp.exec <action_name>; +
-</code> +
- +
-If 'result' is a variable that already exists, 'var' can be omitted: +
- +
-<code lara> +
-   result = $jp.exec <action_name>; +
-</code> +
- +
-The keyword '.exec' can be omitted if you prefix the name of the action with the target join point, and add parenthesis: +
- +
-<code lara> +
-  result = $jp.<action_name>(); +
-</code> +
- +
-==== Calling shell commands ==== +
- +
-You can invoke shell commands from LARA using the function cmd. The first argument is the command, and the second an array with the arguments for the command: +
- +
-<code lara> +
- +
-cmd("ls", ["-l", "-v"]); +
- +
-</code> +
- +
- +
-==== Using LARA from the Command Line ==== +
- +
-=== Include Folder === +
- +
-To add include folders, use the flag -i. To add more than one folder, use double quotes and separate the folders with the file separator character of your current system +
- +
-<code> +
- +
-larai -i "libs1;libs2" +
- +
-</code> +
- +
-=== Passing Arguments to the Aspect === +
- +
-To pass arguments to the top-level aspect use the flag -av. The input is a JSON representation of the input: +
- +
-<code> +
- +
-larai -av "{inputFile:'data.json',execute:true,iterations:10}" +
- +
-</code>  +
- +
- +
-==== Codedef Sections ==== +
- +
-To insert sections of code that span several lines, you can define codedef sections, which act as templates. Example: +
- +
-<code lara> +
- +
-codedef CodeTemplate(param1, param2) %{ +
-// This code is inserted as-is, without escaping +
- +
-// To apply the values of parameters, use [[]] +
-var [[param1]] = [[param2]]; +
- +
-}% end +
- +
-</code> +
- +
-Declared codedefs can then be used in the code as functions: +
- +
-<code lara> +
- +
-code = CodeTemplate("varName", 2); +
- +
-</code> +
- +
-====== Miscellaneous ====== +
- +
-==== Regular Expressions ==== +
- +
-Lara supports JavaScript regular expressions, for instance: +
- +
-<code lara> +
- +
-var regex = /(return\s+)(10)(\s*;)/; +
-regex.test("return 10;"); // Returns 'true' +
- +
-</code> +
- +
-Since **exec** is a LARA keyword, calling **regex.exec** is not permitted. However, you can access object properties using strings to circumvent this limitation: +
- +
-<code lara> +
- +
-(regex['exec']("return 10;"))[2]; // Returns '10' +
- +
-</code> +
- +
-Alternatively, you can also use the **match** function in strings: +
- +
-<code lara> +
- +
-String('aaaa').match(new RegExp('a*')) // Returns 'aaaa' +
- +
-</code> +
- +
-Or you can also use the **match** boolean operator ( **~=** ): +
- +
-<code lara> +
- +
-'aaaa' ~= /a*/ // Returns true +
- +
-</code> +
- +
-==== Importing LARA Files ==== +
- +
-LARA supports importing LARA files (with extension .lara) that are present in the include path (flag -i) using the keyword **import**. To import a file, you have to use the path to the file from the include folder, using '.' as separator and omitting the extension of the file. For instance, if you add as include the folder ~/foo and you want to import the file ~/foo/bar/Aspect.lara, you can write the following code: +
- +
-<code lara> +
- +
-import bar.Aspect; +
- +
-</code> +
- +
-Import statements must be the first statements in a LARA file. LARA weavers come bundled with support for a set of imports, which are part of their API (e.g., [[http://specs.fe.up.pt/tools/clava/doc/|Clava API]]). +
- +
-==== Importing JS Files ==== +
- +
-All JS files (with extension .js) that are present in folders of the include path are automatically evaluated before any LARA file. However, there is a mechanism for importing specific JS files at the same time as LARA files.  +
- +
-When the name of a folder of the include path ends with '-lara', the JS files are not automatically loaded, but instead, must be imported using the keyword **import**. The same rules of importing of LARA files apply. For instance, if you add as include the folder ~/src-lara and you want to import the file ~/src-lara/bar/Foo.js, you can write the following code: +
- +
-<code lara> +
- +
-import bar.Foo; +
- +
-</code> +
- +
- +
-If the folder contains both a Foo.lara and a Foo.js, both files are imported, first the LARA file, and then the JS file. This can be useful if the JS file needs specific imports (the keyword **import** is LARA-specific and is not supported by native JS), in this case the imports can be declared in a LARA file and the rest of the code in a JS file. If both files are connected, we recommend using the same name for both files, with corresponding extensions (.lara and .js). +
- +
-Furthermore, since importing will evaluate all imported LARA and JS scripts in the same context, to help keep things organized, we recommend that LARA/JS scripts declare a single variable/class with the same name as the import (e.g., importing weaver.Query declares a new class Query). +
- +
-Since LARA is based on an older version of JS (i.e. EcmaScript 5), many recent JavaScript features are not available in LARA code. We recommend using JS files in order to have access to more recent features of JavaScript. Currently the LARA framework supports EcmaScript 2021 for JS files. +
-==== Reading/Writing JSON Files ==== +
- +
-LARA supports reading from and writing to JSON objects with the object **Io**: +
- +
-/* <code lara> */ +
-<code javascript> +
-import lara.Io; +
- +
-... +
- +
-Io.writeJson("file.json", anObject); +
-var loadedObject = Io.readJson("file.json"); +
-</code> +
- +
- +
-==== Testing Join Point Types ==== +
- +
-To test if a join point is of a certain type, use the attribute ''.instanceOf(<join_point_name>)''. This respects the join point hierarchy (e.g., "call" and "expr" can both return true) and is more robust than directly checking the name of the join point, i.e. ''$jp.joinPointType === <join_point_name>''. +
- +
-====== Legacy LARA ====== +
- +
-This section contains LARA constructs that are still valid, but for which newer (and recommended) alternatives exist. +
- +
-==== Select ==== +
- +
-(Alternative: Query.search()) +
- +
-Select with full join point chain: +
- +
-<code lara> +
-select program.file.function.body.loop end +
-</code> +
- +
-Select with only last join point. The chain is induced, produces the same result as above: +
- +
-<code lara> +
-select loop end +
-</code> +
- +
-Assign the selected join points to a variable for later use: +
- +
-<code lara> +
-LOOPS: select loop end +
-</code> +
- +
-Assign an alias for specific join points: +
- +
-<code lara> +
-select ($p=loop).($c=loop) end +
-</code> +
- +
-==== Apply ==== +
- +
-(Alternative: for...of on return of Query.search() - i.e. weaver.Selector instances) +
- +
-Apply after a select: +
- +
-<code lara> +
-select loop end +
-apply +
-    println($loop.rank); +
-end +
-</code> +
- +
-Apply on a previously selected set of join points: +
- +
-<code lara> +
-apply to LOOPS +
-    println($loop.rank); +
-end +
-</code> +
- +
-It is possible to perform a natural join on two sets of join points: +
- +
-<code lara> +
-LOOP_START: select function.body.loop.($loop_start = first) end +
-FUNCTION_FIRST: select function.body.first end +
- +
-apply to LOOP_START::FUNCTION_FIRST   +
-    // Init counters at the beginning of the function +
-    $first.insert before%{counter_[[$loop.uid]] = 0;}%; +
- +
-    // Increment counters when entering the loop +
-    $loop_start.insert before%{counter_[[$loop.uid]] = counter_[[$loop.uid]] +1;}%; +
- +
-    // ... +
-end +
-</code> +
- +
-Use of join points with aliases inside the apply statement: +
- +
-<code lara> +
-select ($p=loop).($c=loop) end +
-apply +
-   $p.exec Interchange($c); +
-end +
-</code> +
- +
-==== Conditions ==== +
- +
-(Alternative: Query.search() filters) +
- +
-Using a condition block: +
- +
-<code lara> +
-select function end +
-apply +
-    // ... +
-end +
-condition +
-    $function.name == 'kernel' +
-end +
-</code> +
- +
-Combining conditions using && (and) and || (or) operators: +
- +
-<code lara> +
-select loop end +
-apply +
-    $loop.exec Unroll(2); +
-end +
-condition +
-    $loop.is_innermost && +
-    $loop.type=="for" +
-end +
-</code> +
- +
-Using "filter" conditions on the join point chain: +
- +
-<code lara> +
-select function{name=='kernel'} end +
-apply +
-    // ... +
-end +
- +
-// OR +
-select function{'kernel'} end // uses the default attribute of the join point +
-apply +
-    // ... +
-end +
-</code>+
  
doc/lara.1642271875.txt.gz · Last modified: 2022/01/15 19:37 by jbispo

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