github.com/lmorg/murex@v0.0.0-20240217211045-e081c89cd4ef/docs/user-guide/code-block.md (about) 1 # Code Block Parsing 2 3 > Overview of how code blocks are parsed 4 5 The murex parser creates ASTs ahead of interpreting each block of code. However 6 the AST is only generated for a block at a time. Take this sample code: 7 8 ``` 9 function example { 10 # An example function 11 if { $ENVVAR } then { 12 out 'foobar' 13 } 14 out 'Finished!' 15 } 16 ``` 17 18 When that code is run `function` is executed with the parameters `example` and 19 `{ ... }` but the contents of `{ ... }` isn't converted into ASTs until someone 20 calls `example` elsewhere in the shell. 21 22 When `example` (the Murex function defined above) is executed the parser will 23 then generate AST of the commands inside said function but not any blocks that 24 are associated with those functions. eg the AST would look something like this: 25 26 ``` 27 [ 28 { 29 "Command": "if", 30 "Parameters": [ 31 "{ $ENVVAR }", 32 "then", 33 "{\n out 'foobar'\n }" 34 ] 35 }, 36 { 37 "Command": "out", 38 "Parameters": [ 39 "Finished!" 40 ] 41 } 42 ] 43 ``` 44 45 > Please note this is a mock JSON structure rather than a representation of the 46 > actual AST that would be created. Parameters are stored differently to allow 47 > infixing of variables; and there also needs to be data shared about how 48 > pipelining (eg STDOUT et al) is chained. What is being captured above is only 49 > the command name and parameters. 50 51 So when `if` executes, the conditional (the first parameter) is then parsed and 52 turned into ASTs and executed. Then the last parameter (the **then** block) is 53 parsed and turned into ASTs, if the first conditional is true. 54 55 This sequence of parsing is defined within the `if` builtin rather than 56 Murex's parser. That means any code blocks are parsed only when a builtin 57 specifically requests that they are executed. 58 59 With murex, there's no distinction between text and code. It's up to commands 60 to determine if they want to execute a parameter as code or not (eg a curly 61 brace block might be JSON). 62 63 ## See Also 64 65 * [ANSI Constants](../user-guide/ansi.md): 66 Infixed constants that return ANSI escape sequences 67 * [Pipeline](../user-guide/pipeline.md): 68 Overview of what a "pipeline" is 69 * [Schedulers](../user-guide/schedulers.md): 70 Overview of the different schedulers (or 'run modes') in Murex 71 * [`%(Brace Quote)`](../parser/brace-quote.md): 72 Initiates or terminates a string (variables expanded) 73 * [`%[]` Create Array](../parser/create-array.md): 74 Quickly generate arrays 75 * [`%{}` Create Map](../parser/create-object.md): 76 Quickly generate objects and maps 77 * [`{ Curly Brace }`](../parser/curly-brace.md): 78 Initiates or terminates a code block 79 80 <hr/> 81 82 This document was generated from [gen/parser/codeblock_doc.yaml](https://github.com/lmorg/murex/blob/master/gen/parser/codeblock_doc.yaml).