Atomic Functions
================

.. type:: str

  Strings in Beanquery should be enclosed in *single* quotes.
  Example: ``SELECT * FROM payee == 'Supermarket'``. 
  
  Note: For historical reasons, strings in double quotes can sometimes be used,
  but if they match a column name, they will be interpreted as this column
  name, not a string. Do not use them.

.. type:: bool

  This represents a logical value (yes/no). The acceptable values are ``TRUE``
  or ``FALSE``.

.. type:: set

  This represents a set of values, for example all accounts that are touched
  by a transaction. 

.. type:: int

  A whole number, -1, 0, 1, 2...

.. type:: decimal

  This is a decimal number, as used for example for amounts of currencies 
  or commodities. Example: 1.25.

The following functions can be used to work on basic types: 

* :func:`~fun.abs` - Absolute value.
* :func:`~fun.date` - Convert the argument to a date.
* :func:`~fun.decimal` - Convert the object to a decimal number.
* :func:`~fun.findfirst` - Filter a string sequence by regular expression and return the first match.
* :func:`~fun.getitem` - Get one item from a dict object if it exists, otherwise a default value.
* :func:`~fun.grep` - Match a regular expression against a string and return only the matched portion.
* :func:`~fun.grepn` - Match a pattern with subgroups against a string and return the subgroup at the index.
* :func:`~fun.int` - Convert the object to an integer number.
* :func:`~fun.joinstr` - Join a sequence of strings to a single comma-separated string.
* :func:`~fun.length` - Compute the length of the argument.
* :func:`~fun.lower` - Convert string to lowercase.
* :func:`~fun.maxwidth` - Convert the argument to a substring.
* :func:`~fun.neg` - Negative value.
* :func:`~fun.parse_date` - Parse date from string (first argument).
* :func:`~fun.possign` - Correct sign of an Amount based on the usual balance of associated account.
* :func:`~fun.round` - Round the argument.
* :func:`~fun.safediv` - A division operation that traps division by zero exceptions and outputs zero instead.
* :func:`~fun.splitcomp` - Split a string and extract one of its components.
* :func:`~fun.subst` - Substitute leftmost non-overlapping occurrences of pattern by replacement.
* :func:`~fun.substr` - Extract a substring of the argument.
* :func:`~fun.upper` - Convert string to uppercase.