Module smerl

Copyright © 2006-2007, 2016 AUTHORS Smerl is an Erlang library that simplifies the creation and manipulation of Erlang modules in runtime. You don't need to know Smerl in order to use ErlyWeb; Smerl is included in ErlyWeb because ErlyWeb uses it internally. Smerl uses Erlang's capabilities for hot code swapping and abstract syntax tree transformations to do its magic. Smerl is inspired by the rdbms_codegen.erl module in the RDBMS application written by Ulf Wiger. RDBMS is part of Jungerl ([http://jungerl.sf.net]). Here's a quick example illustrating how to use Smerl: ``` test_smerl() -> M1 = smerl:new(foo), {ok, M2} = smerl:add_func(M1, "bar() -> 1 + 1."), smerl:compile(M2), foo:bar(), % returns 2`` smerl:has_func(M2, bar, 0). % returns true ''' New functions can be expressed either as strings of Erlang code or as abstract forms. For more information, read the Abstract Format section in the ERTS User's guide ([http://erlang.org/doc/doc-5.5/erts-5.5/doc/html/absform.html#4]). Using the abstract format, the 3rd line of the above example would be written as ``` {ok,M2} = smerl:add_func(M1, {function,1,bar,0, [{clause,1,[],[], [{op,1,'+',{integer,1,1},{integer,1,1}}]}]). ''' <p>The abstact format may look more verbose in this example, but it's also easier to manipulate in code.</p>

Authors: Yariv Sadan.

Description

Simple Metaprogramming for Erlang

Data Types

args()

args() = term() | [term()]

error_t()

error_t(Error) = ok | {error, Error}

export()

export() = {Function :: atom(), Arity :: arity()}

exports()

exports() = [export()]

A list of export()s.

func_form()

func_form() = erl_parse:abstract_form()

The abstract form for the function, as described in the ERTS Users' manual.

func_forms()

func_forms() = [func_form()]

A list of func_form()s.

meta_mod()

meta_mod() = 
    #meta_mod{module = module(),
              file = undefined | file:filename(),
              exports = exports(),
              forms = func_forms(),
              export_all = boolean()}

A data structure holding the abstract representation for a module.

ok_t()

ok_t(Value) = {ok, Value} | error

result()

result(Value, Error) = {ok, Value} | {error, Error}

result()

result(Value) = result(Value, term())

Function Index

add_func/2	Add a new exported function to `MetaMod`.
add_func/3	Add `Function` to `MetaMod` and return the new `meta_mod()`.
compile/1	Compile `MetaMod` and load the resulting BEAM into the emulator.
compile/2	Compile `MetaMod` and load the resulting BEAM into the emulator.
curry/2	Get the curried form for `Form` with `Args`.
curry/4	Curry `Module`:`Function`/`Arity` with the given `Args`.
curry/5	Curry `Module`:`Function`/`Arity`with the given `Args`, renaming it to `NewName` and return the renamed form.
curry_add/3	Add `Form` curried with `Args` to `MetaMod`.
curry_add/4	Add `Function`/`Arity` curried with `Args` to `MetaMod`.
curry_add/5	Curry `MetaMod`:`Function`/`Arity` and add it to `MetaMod` as `NewName`.
curry_add/6	Curry `Module`:`Function`/`Arity` and add it to `MetaMod` as `NewName`.
curry_replace/3	Replace the function represented by `Form` in `MetaMod` with its curried form.
curry_replace/4	Replace `Function`/`Arity` in `MetaMod` with its curried form.
embed_all/2	Apply `embed_args/2` with `Values` to all forms in `MetaMod`.
embed_args/2	Replace the arguments of the function represented by `Form`, where the argument's `Name` matches an element from `Vals` with the corresponding `Value`.
embed_args/4	Equivalent to `embed_args(MetaMod, Name, Arity, Values, Name)`.
embed_args/5	Apply `embed_args/2` to `MetaMod`:`Function`/`Arity` and add the resulting function to `MetMod`, after renaming it to `NewName`.
extend/2	Add aliases for `Parent`'s functions missing from `Child` to `Child`.
extend/3	Similar to `extend/2`, with the addition of `ArityDiff`, which indicates the difference in arities Smerl should use when figuring out which functions to generate based on the modules' exports.
extend/4
for_file/1	Equivalent to `for_file(SrcFilePath, [])`.
for_file/2	Equivalent to `for_file(SrcFilePath, IncludePaths, [])`.
for_file/3	Create a meta_mod for a module from its source file.
for_module/1	Equivalent to `for_module(ModuleName, [])`.
for_module/2	Equivalent to `for_module(ModuleName, IncludePaths, [])`.
for_module/3	Create a meta_mod tuple for an existing module.
get_attribute/2	Get the value of `MetaMod`'s `Key` attribute.
get_export_all/1	Get the `export_all` value for `MetaMod`.
get_exports/1	Return the list of exports in the meta_mod.
get_forms/1	Return the list of function forms in the meta_mod.
get_func/3	Attempt to get the `func_form()` for `MetaMod`:`Function`/`Arity`.
get_module/1	Return the module name for the meta_mod.
has_func/3	Check whether `MetaMod` has a function `Function`/`Arity`.
new/1	Create a new meta_mod for a module with the given name.
remove_export/3	Remove an export `{Function, Arity}` from the list of `exports` in `MetaMod`.
remove_func/3	Try to remove `Function` from `MetaMod`.
rename/2	Change the name of the function represented by `Form` to `NewName`.
replace_func/2	Replace an existing function with a new one.
set_export_all/2	Set the `export_all` value for `MetaMod`.
set_exports/2	Set the `MetaMod`'s export list to `Exports`.
set_forms/2
set_module/2	Set the meta_mod's module name.
to_src/1	Return the pretty-printed source code for `MetaMod`.
to_src/2	Equivalent to `file:write_file(Filename, to_src(MetaMod))`.

Function Details

add_func/2

add_func(MetaMod, Form) -> result(meta_mod(), parse_error)

```
MetaMod = meta_mod()
```
```
Form = func_form() | string()
```

Equivalent to add_func(MetaMod, Form, true).

Add a new exported function to MetaMod.

add_func/3

add_func(MetaMod, Func, Export) -> result(meta_mod(), parse_error)

```
MetaMod = meta_mod()
```
```
Func = func_form() | string()
```
```
Export = boolean()
```

Add Function to MetaMod and return the new meta_mod(). If Export is true, add Function to MetaMod's exports.

compile/1

compile(MetaMod :: meta_mod()) -> error_t(term())

Equivalent to compile(MetaMod, []).

Compile MetaMod and load the resulting BEAM into the emulator.

compile/2

compile(MetaMod, Options) -> error_t(term())

```
MetaMod = meta_mod()
```
```
Options = [proplists:property()]
```

Equivalent to compile(MetaMod, [report_errprs, report_warnings, return_errors]).

Compile MetaMod and load the resulting BEAM into the emulator. Options is a list of options as described in the compile module in the Erlang documentation. If an outdir is provided, write the .beam file to it.

curry/2

curry(Form :: func_form(), Args :: args()) -> result(func_form())

Get the curried form for Form with Args. Here, "currying" involves replacing one or more of the function's leading arguments with predefined values.

curry/4

curry(Module, Function, Arity, Args) -> result(func_form())

```
Module = module() | meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Args = args()
```

Curry Module:Function/Arity with the given Args.

curry/5

curry(Module, Function, Arity, Args, NewName) ->
         result(func_form())

```
Module = module() | meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Args = args()
```
```
NewName = atom()
```

Curry Module:Function/Aritywith the given Args, renaming it to NewName and return the renamed form.

curry_add/3

curry_add(MetaMod, Form, Args) -> result(meta_mod())

```
MetaMod = meta_mod()
```
```
Form = func_form()
```
```
Args = args()
```

Add Form curried with Args to MetaMod.

curry_add/4

curry_add(MetaMod, Function, Arity, Args) -> result(meta_mod())

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Args = args()
```

Add Function/Arity curried with Args to MetaMod.

curry_add/5

curry_add(MetaMod, Function, Arity, Args, NewName) -> Result

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Args = args()
```
```
NewName = atom()
```

Result = result(meta_mod(), parse_error)

Curry MetaMod:Function/Arity and add it to MetaMod as NewName.

curry_add/6

curry_add(MetaMod, Module, Function, Arity, Args, NewName) ->
             Result

```
MetaMod = meta_mod()
```
```
Module = module() | meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Args = args()
```
```
NewName = atom()
```
```
Result = result(meta_mod())
```

Curry Module:Function/Arity and add it to MetaMod as NewName.

curry_replace/3

curry_replace(MetaMod, Form, Args) -> result(meta_mod())

```
MetaMod = meta_mod()
```
```
Form = func_form()
```
```
Args = args()
```

Replace the function represented by Form in MetaMod with its curried form.

curry_replace/4

curry_replace(MetaMod, Function, Arity, Args) ->
                 result(meta_mod())

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Args = args()
```

Replace Function/Arity in MetaMod with its curried form.

embed_all/2

embed_all(MetaMod, Values) -> NewMod

```
MetaMod = meta_mod()
```

Values = [{Name :: atom(), Value :: term()}]

```
NewMod = meta_mod()
```

Apply embed_args/2 with Values to all forms in MetaMod. exports for functions whose arities change are preserved.

embed_args/2

embed_args(Form, Vals) -> NewForm

```
Form = func_form()
```

Vals = [{Name :: atom(), Value :: term()}]

```
NewForm = func_form()
```

Replace the arguments of the function represented by Form, where the argument's Name matches an element from Vals with the corresponding Value.

embed_args/4

embed_args(MetaMod, Function, Arity, Values) -> result(meta_mod())

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Values = proplists:proplist()
```

Equivalent to embed_args(MetaMod, Name, Arity, Values, Name).

embed_args/5

embed_args(MetaMod, Function, Arity, Values, NewName) -> Result

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
Values = proplists:proplist()
```
```
NewName = atom()
```
```
Result = result(meta_mod())
```

Apply embed_args/2 to MetaMod:Function/Arity and add the resulting function to MetMod, after renaming it to NewName.

See also: rename/2.

extend/2

extend(Parent, Child) -> NewChildMod

```
Parent = module() | meta_mod()
```
```
Child = module() | meta_mod()
```
```
NewChildMod = meta_mod()
```

Add aliases for Parent's functions missing from Child to Child. The new functions in Child are shallow, i.e. they have the name and arity of the corresponding functions in Parent, but instead of implementing their logic they call the Parent functions.

extend/3

extend(Parent, Child, ArityDiff) -> NewChildMod

```
Parent = module() | meta_mod()
```
```
Child = module() | meta_mod()
```
```
ArityDiff = non_neg_integer()
```
```
NewChildMod = meta_mod()
```

Similar to extend/2, with the addition of ArityDiff, which indicates the difference in arities Smerl should use when figuring out which functions to generate based on the modules' exports. This is sometimes useful when calling extend/3 followed by embed_all/2.

extend/4

extend(Parent, Child, ArityDiff, Options) -> NewChildMod

```
Parent = module() | meta_mod()
```
```
Child = module() | meta_mod()
```
```
ArityDiff = non_neg_integer()
```
```
Options = [proplists:property()]
```
```
NewChildMod = meta_mod()
```

for_file/1

for_file(SrcFilePath) -> any()

Equivalent to for_file(SrcFilePath, []).

for_file/2

for_file(SrcFilePath, IncludePaths) -> any()

Equivalent to for_file(SrcFilePath, IncludePaths, []).

for_file/3

for_file(SrcFilePath, IncludePaths, Macros) -> Result

```
SrcFilePath = file:filename()
```
```
IncludePaths = [file:filename()]
```
```
Macros = [{module(), atom()}]
```

Result = result(meta_mod(), invalid_module)

Create a meta_mod for a module from its source file.

for_module/1

for_module(ModuleName) -> any()

Equivalent to for_module(ModuleName, []).

for_module/2

for_module(ModuleName, IncludePaths) -> any()

Equivalent to for_module(ModuleName, IncludePaths, []).

for_module/3

for_module(ModuleName, IncludePaths, Macros) -> result(meta_mod)

```
ModuleName = atom() | string()
```
```
IncludePaths = [string()]
```
```
Macros = [{atom(), term()}]
```

Create a meta_mod tuple for an existing module. If ModuleName is a string, it is interpreted as a file name (this is the same as calling for_file/3). If ModuleName is an atom, Smerl attempts to find its abstract represtation either from its source file or from its .beam file directly (if it has been compiled with debug_info). If the abstract representation can't be found, this function returns an error.

The IncludePaths argument is used when ModuleName is a file name.

get_attribute/2

get_attribute(MetaMod :: meta_mod(), Key :: atom()) ->
                 result(term())

Get the value of MetaMod's Key attribute.

get_export_all/1

get_export_all(MetaMod :: meta_mod()) -> boolean()

Get the export_all value for MetaMod.

get_exports/1

get_exports(MetaMod :: meta_mod()) -> exports()

Return the list of exports in the meta_mod.

get_forms/1

get_forms(MetaMod :: meta_mod()) -> func_forms()

Return the list of function forms in the meta_mod.

get_func/3

get_func(MetaMod, Function, Arity) -> result(func_form())

```
MetaMod = meta_mod() | module()
```
```
Function = atom()
```
```
Arity = arity()
```

Attempt to get the func_form() for MetaMod:Function/Arity.

get_module/1

get_module(MetaMod :: meta_mod()) -> module()

Return the module name for the meta_mod.

has_func/3

has_func(MetaMod, Function, Arity) -> boolean()

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```

Check whether MetaMod has a function Function/Arity.

new/1

new(Module :: module()) -> meta_mod()

Create a new meta_mod for a module with the given name.

remove_export/3

remove_export(MetaMod, Function, Arity) -> NewMod

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
NewMod = meta_mod()
```

Remove an export {Function, Arity} from the list of exports in MetaMod.

remove_func/3

remove_func(MetaMod, Function, Arity) -> NewMod

```
MetaMod = meta_mod()
```
```
Function = atom()
```
```
Arity = arity()
```
```
NewMod = meta_mod()
```

Try to remove Function from MetaMod. If the function exists, return the new meta_mod(). Otherwise, return MetaMod.

rename/2

rename(Form :: func_form(), NewName :: atom()) -> func_form()

Change the name of the function represented by Form to NewName.

replace_func/2

replace_func(MetaMod, Function) -> result(meta_mod())

```
MetaMod = meta_mod()
```
```
Function = string() | func_form()
```

Replace an existing function with a new one. If a matching function doesn't exist, add Function to MetaMod. This is tantamount to calling remove_func/3 followed by add_func/2.

set_export_all/2

set_export_all(MetaMod, Value) -> NewMod

```
MetaMod = meta_mod()
```
```
Value = boolean()
```
```
NewMod = meta_mod()
```

Set the export_all value for MetaMod.

set_exports/2

set_exports(MetaMod, Exports) -> NewMod

```
MetaMod = meta_mod()
```
```
Exports = exports()
```
```
NewMod = meta_mod()
```

Set the MetaMod's export list to Exports.

set_forms/2

set_forms(MetaMod, Forms) -> NewMod

```
MetaMod = meta_mod()
```
```
Forms = func_forms()
```
```
NewMod = meta_mod()
```

set_module/2

set_module(MetaMod, NewName) -> NewMod

```
MetaMod = meta_mod()
```
```
NewName = module()
```
```
NewMod = meta_mod()
```

Set the meta_mod's module name.

to_src/1

to_src(MetaMod :: meta_mod()) -> Source :: string()

Return the pretty-printed source code for MetaMod.

to_src/2

to_src(MetaMod, Filename) -> error_t(term())

```
MetaMod = meta_mod()
```
```
Filename = file:filename()
```

Equivalent to file:write_file(Filename, to_src(MetaMod)).