what is the meaning of a た形の動詞　＋　とする


The sentence is 例えば外食時、定食屋さんでとても美味しいご飯をたべたとする。

I've looked at some other answered questions which explain how とする, when
appended to a verb expresses quitting an old action and starting a new one.
However I can't understand it in this case, because it seems odd that it would
be used in the past tense.

Does it take on a different meaning if the verb is in the past tense?




`clause + とする` can mean "assume ～", "suppose ～", "regard ～", "let ～", etc. So
the sentence means "Suppose you eat ..."

Examples and explanations are found on the following sites:

  * [Hypothesizing and Concluding | Learn Japanese](http://www.guidetojapanese.org/learn/grammar/reasoning)
  * [とする (tosuru) | JGram - The Japanese Grammar database](http://www.jgram.org/pages/viewOne.php?tagE=tosuru)

The ta-form is [used in combination of many hypothetical or conditional
expressions](https://japanese.stackexchange.com/q/393/5010). I think this ta-
form is for denoting the perfect aspect, not the past tense. 定食屋さんでご飯をたべるとする
refers to what you would think/plan/do before eating a meal (e.g., choosing a
good restaurant). 定食屋さんでご飯をたべたとする refers to what you would think/do at a
mealtime or after the meal (e.g., paying with a credit card).




`clause + とする` can mean "assume ～", "suppose ～", "regard ～", "let ～", etc. So
the sentence means "Suppose you eat ..."

Examples and explanations are found on the following sites:

  * [Hypothesizing and Concluding | Learn Japanese](http://www.guidetojapanese.org/learn/grammar/reasoning)
  * [とする (tosuru) | JGram - The Japanese Grammar database](http://www.jgram.org/pages/viewOne.php?tagE=tosuru)

The ta-form is [used in combination of many hypothetical or conditional
expressions](https://japanese.stackexchange.com/q/393/5010). I think this ta-
form is for denoting the perfect aspect, not the past tense. 定食屋さんでご飯をたべるとする
refers to what you would think/plan/do before eating a meal (e.g., choosing a
good restaurant). 定食屋さんでご飯をたべたとする refers to what you would think/do at a
mealtime or after the meal (e.g., paying with a credit card).

