# Method lfun::_sprintf()

Method _sprintf

  ``string` _sprintf(`int` `conversion_type`, `mapping`(`string`:`int`)|`void` `params`)`

Description

  Sprintf callback.

  This method is called by sprintf() to print objects. If it is not present, printing of the object will not be supported for any conversion-type except for the `%O`-conversion-type, which will output `"object"`.

Parameter `conversion_type`

  One of:

  ``'b'`` | Signed binary integer.
  ``'d'`` | Signed decimal integer.
  ``'u'`` | Unsigned decimal integer.
  ``'o'`` | Signed octal integer.
  ``'x'`` | Lowercase signed hexadecimal integer.
  ``'X'`` | Uppercase signed hexadecimal integer.
  ``'c'`` | Character. If a fieldsize has been specified this will output the low-order bytes of the integer in network byte order.
  ``'f'`` | Float.
  ``'g'`` | Heuristically chosen representation of float.
  ``'G'`` | Like `%g`, but uses uppercase `E` for exponent.
  ``'e'`` | Exponential notation float.
  ``'E'`` | Like `%e`, but uses uppercase `E` for exponent.
  ``'s'`` | String.
  ``'O'`` | Any value (debug style).
  ``'t'`` | Type of the argument.

Parameter `params`

  Conversion parameters. The following parameters may be supplied:

  ``"precision"` : `int`` | Precision.
  ``"width"` : `int`` | Field width.
  ``"flag_left"` : `int(1..1)`` | Indicates that the output should be left-aligned.
  ``"indent"` : `int`` | Indentation level in `%O`-mode.

Returns

  Is expected to return a string describing the object formatted according to `conversion_type`.

Note

  _sprintf() is currently not called for the following conversion-types:

  ``'F'`` | Binary IEEE representation of float (`%4F` gives single precision, `%8F` gives double precision.)

Note

  This function might be called at odd times, e.g. before lfun::create has been called or when an error has occurred. The reason is typically that it gets called when a backtrace is being formatted to report an error. It should therefore be very robust and not make any assumptions about its own internal state, at least not when `conversion_type` is `'O'`.

Note

  It's assumed that this function is side-effect free.

See also

  sprintf()