請問have had/has had應該幾時同點用

諗唔到究竟平時對話或者email可以點用
請問有冇簡單例子可以指教？

have had vs had
前者強調由一個時間點到present已經持續一段時間，
後者只係話俾你聽以前發生過，冇強調持續幾耐or specific time point

試下用warn做例子：

i have warned u.
我已經警告過你好L多次。
→強調自己持續一段時間已經一直警告你

i warned u.
我警告過你。
→冇強調幾多次，淨係表達「警告過」嘅意思

present perfect tense黎架喎

唔該兩位，但係我都仲唔係好明
有冇多少少例子？

請問中文或者廣東話有冇咁嘅用法呢？

試下加咗time point會唔會好啲？

i had mcdonalds for breakfast this morning.
我今朝食咗m記。

i have had mcdonalds for breakfast for weeks.
我食咗好幾個禮拜m記啦。

你個例子同上面又有分別，你呢個係一段時間
上面就只係普通過去完成

想搭單問
Present prefect (have had) 同 simple past (had)
係咪好多時都可以互相交換用？ 文法上冇錯
但意思上有少許分別？

I have eaten lunch (強調已經食左 可能有人約我食lunch)
I ate lunch (單純話你知今日食左飯）

sorry有少少離題
如果第一句係用係this week over 咁點解唔係用last week
I had a lot of assignments last week

I had a take-home exam last year.
I have three assignments due next Monday.
I have already had so many assignments in the first few weeks of this new course.

- - -

2008 had a financial turmoil.
From 2006 to 2007, it had had numerous events leading up to the financial crisis in 2008.
2020 has had so many dramatic incidents.

第二句例句唔係錯咩?如果講specific既時間要用past tense

第二句冇錯如果this week未完
如果今日係星期六，就可以用past tense

打字打到上手就會自動波. Also, I don’t really care.... as long as people understand

多數唔可以互用 文法會錯
你嘅例子文法上無錯
但通常講食嘢唔會用eat lunch 會用have lunch

E.g. Do you wanna have lunch with us?
: I’ve had lunch already. / I’ve eaten just now.
(Present perfect)

E.g. What did you do during break time?
: I had lunch. / I ate.
(Past tense)