# Concat

String concatenation

## Signature

concat(expr: AttrName|(Tuple->Numeric)) -> Aggregator

## Examples
concat(:name)
concat(:name, between: ', ')
concat(between: ', '){|t| t.name }
concat(->(t){ t.name.upcase }, between: ', ')

## Description

Concatenates string representations of input values.

## Implementation notes

This aggregate function can be applied to any data type, not only String
attributes. Ruby's `to_s` will be used on values prior to concatenation.

The options are:

* `before` starts the resulting string (defaults to '')
* `after` ends the resulting string (defaults to '')
* `between` is used between each value

As of current Alf version, the order in which the values are concatenated
is not guaranteed. So far, this function is thus non-deterministic.