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# erl_id_trans (stdlib v7.1)

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This module performs an identity parse transformation of Erlang code.

It is included as an example for users who wants to write their own parse transformers. If option `{parse_transform,Module}` is passed to the compiler, a user-written function `parse_transform/2` is called by the compiler before the code is checked for errors.

Before the function `parse_transform/2` is called, the Erlang Compiler checks if the parse transformation can handle abstract code with column numbers: If the function `parse_transform_info/0` is implemented and returns a map where the key `error_location` is associated with the value `line`, the compiler removes column numbers from the abstract code before calling the parse transform. Otherwise, the compiler passes the abstract code on without modification.

## Parse Transformations

Parse transformations are used if a programmer wants to use Erlang syntax, but with different semantics. The original Erlang code is then transformed into other Erlang code.

#### Note

Programmers are strongly advised not to engage in parse transformations. No support is offered for problems encountered.

## See Also

`erl_parse` and `compile`.

# Summary

## Functions

parse_transform(Forms, Options)

Performs an identity transformation on Erlang forms, as an example.

parse_transform_info()

Returns information about the parse transform itself.

# Functions

# parse_transform(Forms, Options)

    -spec parse_transform(Forms, Options) -> NewForms
                             when
                                 Forms :: [erl_parse:abstract_form() | erl_parse:form_info()],
                                 NewForms :: Forms,
                                 Options :: [compile:option()].

Performs an identity transformation on Erlang forms, as an example.

# parse_transform_info()

(since OTP 24.0)

    -spec parse_transform_info() -> #{error_location => column | line}.

Returns information about the parse transform itself.