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Syntax_Tools
User's Guide
Version 1.6.7.2

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# 1 Erlang Syntax Tools

### 1.1 Overview

This package contains modules for handling abstract Erlang syntax trees, in a way that is compatible with the "parse trees" of the standard library module erl_parse, together with utilities for reading source files in unusual ways and pretty-printing syntax trees. Also included is an amazing module merger and renamer called Igor, as well as an automatic code-cleaner.

The abstract layer (defined in erl_syntax) is nicely structured and the node types are context-independent. The layer makes it possible to transparently attach source-code comments and user annotations to nodes of the tree. Using the abstract layer makes applications less sensitive to changes in the erl_parse(3) data structures, only requiring the erl_syntax module to be up-to-date.

The pretty printer erl_prettypr is implemented on top of the library module prettypr: this is a powerful and flexible generic pretty printing library, which is also distributed separately.

For a short demonstration of parsing and pretty-printing, simply compile the included module demo.erl, and execute demo:run() from the Erlang shell. It will compile the remaining modules and give you further instructions.

Also try the erl_tidy module, as follows:

        erl_tidy:dir("any-erlang-source-dir", [test, old_guard_tests]).

("test" assures that no files are modified).

News in 1.4:

- Added support for cond-expressions, try-expressions and class-qualifier patterns.

- Added support for parameterized modules.

- Igor is officially included.

- Quick-parse functionality added to epp_dodger.

News in 1.3:

- Added support for qualified names (as used by "packages").

- Various internal changes.

News in 1.2:

- HTML Documentation (generated with EDoc).

- A few bug fixes and some minor interface changes (sorry for any inconvenience).

News in 1.1:

- Module erl_tidy: check or tidy either a single module, or a whole directory tree recursively. Rewrites and reformats the code without losing comments or expanding macros. Safe mode allows generating reports without modifying files.

- Module erl_syntax_lib: contains support functions for easier analysis of the source code structure.

- Module epp_dodger: Bypasses the Erlang preprocessor - avoids macro expansion, file inclusion, conditional compilation, etc. Allows you to find/modify particular definitions/applications of macros, and other things previously not possible.