What is the function of と in verb-ていると form


I read this sentence in a book for beginners, but I can't find the grammar in
any of my books or online:

> おばあさんが川で洗濯をしていると、川上のほうから、大きな桃が「どんぶらこ、どんぶらこ」と流れてきました。

Which I translate as

> While the old woman was washing in the river, a big peach came floating down
> from upstream (with some sound effects).

However, I can't find any references that mention that the verb in -ている form
followed by と should mean "while". Or indeed any references to such a
construct at all. Can someone please explain this grammar, how common it is,
and when it is right to use it? Note that I am familiar with the verb-ている form
when referring to "verb-ing" or when there is a change of state. I'm also
happy that と after a verb can mean "if", but that doesn't seem to work here.

Many thanks




It is indeed the conditional と but takes more of the form of 'when' rather
than 'if', in a similar way to how とき is used. You'll see it used in this way
quite a lot. This also means that anything before と doesn't necessarily have a
cause-effect relationship. It's not _because_ the the women was doing her
laundry by the river that the peach came.

[code]

    それは先生に聞くとすぐ分かった　(I understood immediately when i asked my teacher) - DOBJG pg.481
    
[/code]

[http://en.wiktionary.org/wiki/と](http://en.wiktionary.org/wiki/%E3%81%A8)




It is indeed the conditional と but takes more of the form of 'when' rather
than 'if', in a similar way to how とき is used. You'll see it used in this way
quite a lot. This also means that anything before と doesn't necessarily have a
cause-effect relationship. It's not _because_ the the women was doing her
laundry by the river that the peach came.

[code]

    それは先生に聞くとすぐ分かった　(I understood immediately when i asked my teacher) - DOBJG pg.481
    
[/code]

[http://en.wiktionary.org/wiki/と](http://en.wiktionary.org/wiki/%E3%81%A8)

