Is this と (particle) + したら　or is it "としたら"


It's an exercise from my textbook where I have to fill in a word from a list.
The list is: なる, 渡る, 話す, できる, たいへんな, 降りる.

The sentence in question is as follows:

> 電車を _______ **としたら** 、ドアが閉まってしまった。

I don't think that と+したら could make any sense here, but my textbook hasn't
taught me the word としたら <http://jisho.org/search/toshitara> yet so I can't
rule it out. That's why I'm asking you what you think.

I would insert 降りる here and translate the sentence as follows: "If it happens
that I exit the train, unfortunately the door will close."




降りる is obviously the verb you want, but I think the exercise must expect you
to put it into the tentative form, 降りよう. 降りようとしたら, "When I made to get off",
"Just as I was going to get off", would make sense here. I expect you know the
rule:

> Tentative form + とする = make as if to do, be about to do, be going to do, be
> on the point of doing, try [unsuccessfully] to do.

For example:

>   * お風呂に入ろうとすると, "just as I was about to get into the bath [the telephone
> rang]"
>   * 10時になろうとしています "[Radio announcer] It's just coming up to ten o'clock"
>   * 窓を開けようとしたが "I tried to open the window [but it was jammed]".
>

So your completed sentence would mean "Just as I was going to get off the
train, the door closed" (or maybe "the damned door" to convey the irritation
expressed by しまった)




降りる is obviously the verb you want, but I think the exercise must expect you
to put it into the tentative form, 降りよう. 降りようとしたら, "When I made to get off",
"Just as I was going to get off", would make sense here. I expect you know the
rule:

> Tentative form + とする = make as if to do, be about to do, be going to do, be
> on the point of doing, try [unsuccessfully] to do.

For example:

>   * お風呂に入ろうとすると, "just as I was about to get into the bath [the telephone
> rang]"
>   * 10時になろうとしています "[Radio announcer] It's just coming up to ten o'clock"
>   * 窓を開けようとしたが "I tried to open the window [but it was jammed]".
>

So your completed sentence would mean "Just as I was going to get off the
train, the door closed" (or maybe "the damned door" to convey the irritation
expressed by しまった)

