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Parsing

Parsing language files in an editor is configured in the language section of an ESV file. The syntax is as follows:

language

  table         : $Path
  start symbols : $Sorts

  line comment  : $String
  block comment : $String * $String
  fences        : $Fences

For example:

language

  table         : target/metaborg/sdf.tbl
  start symbols : File

  line comment  : "//"
  block comment : "/*" * "*/"
  fences        : [ ] ( ) { }

Parse Table

The parse table of your language is set with the table key. By default, the parse table of an SDF specification is always produced at target/metaborg/sdf.tbl. It is only necessary to change this configuration when a custom parse table is used.

Start Symbols

The start symbols key determine which start symbols to use when an editor is opened. This must be a subset of the start symbols defined in the SDF3 specification of your language.

Multiple start symbols can be set with a comma-separated list:

language

  start symbols : Start, Program

Comments

The syntax for comments is:

language

  line comment  : $String
  block comment : $String * $String

For example, Java comments are specified as:

language

  line comment  : "//"
  block comment : "/*" * "*/"

The line comment key determines how single-line comments are created. It is used by editors to toggle the comment for a single line. For example, in Eclipse, pressing Ctrl+/ (Cmd+/ on macOS), respectively comments or uncomments the line. The block comment key determines how multi-line comments are created. It is used when a whole block needs to be commented or uncommented. A block comment is described by the two strings denoting the start and end symbols of the block comment respectively.

Fences

Fences for bracket matching are set as follows:

language

  fences : $Fences

The fences key determines which symbols to use and match for bracket matching. A single fence is defined by a starting and closing symbol. Multiple fences can be set with a space-separated list. Fences are used to do bracket matching in text editors.

For example, the default fences in a new Spoofax language project are:

language

  fences : [ ] ( ) { }

Multi-Character Fences

Fences can contain multiple characters, but some implementations may not handle bracket matching with multiple fence characters. For example, Eclipse does not handle this case and ignores multi-character fences.


Last update: 2021-11-15
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