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If you'd have performed the operation yesterday like you were supposed to...
如果你按計劃昨天就給我做手術(shù)
...I'd be sucking carrots through a straw in my arm.
我現(xiàn)在就能用吸管喝胡蘿卜汁了。
關(guān)于if引導(dǎo)的虛擬語氣
1. 虛擬條件句時態(tài)的基本特點：虛擬條件句可以表示過去，現(xiàn)在和將來的情況，時態(tài)的基本特點是時態(tài)往后推移。
1).對現(xiàn)在的虛擬;if條件從句用一般過去時（be用were），主句用should（would）等 +動詞原形。如;高三冊unit 8 8單元p69：If I hadn’t piles of homework to do , I would relax. 如果我沒有成堆的作業(yè)要做，我就會輕松。（事實上我有許多作業(yè)要做，不能放松）注意：在虛擬語氣的從句中，動詞'be'的過去時態(tài)一律用"were"，不用was，即在從句中be用were代替。如： If I were you, I would go there. 如果我是你，我就會去那兒。
2). 對過去的虛擬:if條件從句用過去完成時(had done),主句用should（would）等+ have done.如：高三冊unit 8 p70：If it hadn’t had a flat tyre , I should / would have lent my car to George that morning .如果車沒有一個癟輪胎的話，我那天上午會把車借給喬治的。（事實上車有一個癟輪胎，我那天上午沒有把車借給喬治）
3). 表示對將來不大可能發(fā)生的事情的虛擬:if條件從句用一般過去時（be用were）/were+ to do /should+ 動詞原形,主句用should/would等 + 動詞原形. 如：If you succeeded/ should succeed / were to succeed, everything would be OK. 如果你將來成功了，一切都會好的.
2. 錯綜條件句：主句與從句的動作發(fā)生在不同的時間，主句從句謂語動詞的虛擬語氣形式因時間不同而不同，這種條件句叫做混合條件句。主要的考點是if條件從句是對過去的虛擬用had done，主句是對現(xiàn)在的虛擬用should/would等 + 動詞原形。
如：高三冊unit 8 p70：If I had been brought in Britain as my cousin was, I would speak English as she does . （從句與過去事實相反，主句與現(xiàn)在事實相反。）
If you had asked him yesterday, you would know what to do now. 如果你昨天問過他，今天就知道做什么了。
If it had rained last night（過去）, it would be very cold today （現(xiàn)在）.如果昨晚下過雨，今天就會很冷了。
3. 虛擬條件句中的省略和倒裝：虛擬條件句的if從句部分含有were, should, 或had時, 可省略if，然后把were, should或had 移至從句的句首，進行倒裝。主句部分保持不變。
如：高三冊unit 8 p70：If I had been brought in Britain as my cousin was，…=Had I been brought in Britain as my cousin was ，…
高三冊8單元p70：If it hadn’t had a flat tyre , I would have lent my car to George that morning = Had it not had a flat tyre, I would have lent my car to George that morning
Were they here now( =If they were here now ), they could help us.如果他們現(xiàn)在在的話，就能幫助我們了。
Should it rain（=If it should rain）, the crops would be saved., the crops would be saved.假如下雨，莊稼就有救了。
