glite/decode

Decoders that turn a result row into a typed value.

import glite/decode

let user = {
  use id <- decode.element(0, decode.int)
  use name <- decode.element(1, decode.text)
  use email <- decode.element(2, decode.optional(decode.text))
  decode.success(User(id:, name:, email:))
}

Types

RowDecoder

opaque </>

Decodes one row, a list of column values.

pub opaque type RowDecoder(a)

ValueDecoder

</>

Decodes one column value. The error is a short description.

pub type ValueDecoder(a) =
  fn(value.Value) -> Result(a, String)

Values

blob

</>

pub fn blob(value: value.Value) -> Result(BitArray, String)

Binary data. Text is accepted too, as its UTF-8 bytes, because SQLite doesn’t always say which of the two a value is.

bool

</>

pub fn bool(value: value.Value) -> Result(Bool, String)

A boolean stored as the integer 0 or 1.

element

</>

pub fn element(
  index: Int,
  decoder: fn(value.Value) -> Result(a, String),
  next: fn(a) -> RowDecoder(b),
) -> RowDecoder(b)

Decode the column at index, counting from 0, then carry on with next. Made for use.

float

</>

pub fn float(value: value.Value) -> Result(Float, String)

A float.

int

</>

pub fn int(value: value.Value) -> Result(Int, String)

An integer.

optional

</>

pub fn optional(
  decoder: fn(value.Value) -> Result(a, String),
) -> fn(value.Value) -> Result(option.Option(a), String)

NULL becomes None; anything else goes through decoder.

raw

</>

pub fn raw(value: value.Value) -> Result(value.Value, String)

The value as it is.

run

</>

pub fn run(
  decoder: RowDecoder(a),
  row: List(value.Value),
  at row_index: Int,
) -> Result(a, error.Error)

Run a decoder on one row. row is the row’s position in its result, used in the error.

success

</>

pub fn success(value: a) -> RowDecoder(a)

Finish a decoder with a value.

text

</>

pub fn text(value: value.Value) -> Result(String, String)

Text.