# `Cldr.DateTime.Format.Compiler`
[🔗](https://github.com/elixir-cldr/cldr_dates_times/blob/v2.25.6/lib/cldr/format/compiler.ex#L1)

Tokenizes and parses `Date`, `Time` and `DateTime` format strings.

During compilation, each of the date, time and datetime format
strings defined in CLDR are compiled into a list of
function bodies that are then grafted onto the function head
`format/3` in a backend module.  As a result these compiled
formats execute with good performance.

For formats not defined in CLDR (ie a user defined format),
the tokenizing and parsing is performed, then list of function
bodies is created and then `format/3`
recurses over the list, invoking each function and
collecting the results.  This process is significantly slower
than that of the precompiled formats.

User defined formats can also be precompiled by configuring
them under the key `:precompile_datetime_formats`.  For example:

    config :ex_cldr,
      precompile_datetime_formats: ["yy/dd", "hhh:mmm:sss"]

# `compile`

```elixir
@spec compile(String.t(), module(), module()) ::
  {:ok, Macro.t()} | {:error, String.t()}
```

Parse a date, time or datetime format string.

## Arguments

* `format_string` is a string defining how a date/time/datetime
is to be formatted.  See `Cldr.DateTime.Formatter` for the list
of supported format symbols.

## Returns

Returns a list of function bodies which are grafted onto
a function head in `Cldr.DateTime.Formatter` at compile time
to produce a series of functions that process a given format
string efficiently.

# `tokenize`

Tokenize a date, time or datetime format string.

This function is designed to produce output
that is fed into `Cldr.DateTime.Format.Compiler.compile/3`.

## Arguments

* `format_string` is a date, datetime or time format
  string.

## Returns

A list of 3-tuples which represent the tokens
of the format definition.

## Example

    iex> Cldr.DateTime.Format.Compiler.tokenize("yyyy/MM/dd")
    {:ok,
     [{:year, 1, 4}, {:literal, 1, "/"}, {:month, 1, 2}, {:literal, 1, "/"},
      {:day_of_month, 1, 2}], 1}

# `tokenize_format_string`

---

*Consult [api-reference.md](api-reference.md) for complete listing*