if引导的句子,是否都是主句用将来时（祈使句除外）,从句用现在时?

if引导的句子,是否都是主句用将来时（祈使句除外）,从句用现在时?

不是,条件句主要有四种类型的条件句：
1.If you heat ice,it melts.
2.If we catch the 10 o'clock train,we shall(will,can,may)get there by lunch-time.
3.If we caught the 10 o'clock train,we would(could,might)get there by lunch-time.
4.If we had caught the 10o'clock train,we would
(could,might)have got there by lunch-time.
第一种类型：
是真实条件句的一种.在这种条件句中,if的意义接近于whenever,所以这种句型又叫“whenever-型“,可用于三种场合：
1）表示普遍真理和客观事实,e.g.If you pour oil on water,it floats.
2）表示现在习惯动作,e.g.If I make a promise,I keep it.
3) 表示过去习惯动作,e.g.If I made a promise,I kept it.
第二种类型：
是真实条件句的主体,最普通,最常用.这种句式又可分为三种形式：
1）“基本形式”,If it is fine tomorrow,we can(will)have a picnic somewhere.(主将从现）和If you wake up before me,give me a call.（主句用祈使句）
2）“变体形式”,是上述基本形式的三种变体形式：
A.If we should miss the 10 o'clock train,we shan't get there till after lunch.（这里,should 仅表示一种不太肯定的婉转口气,并不影响条件的真实性.）
B.If you will reserve seats,we shall be sure of a comfortable journey.（这里的will并不单纯表示将来意义,而表示“意愿”的情态助动词,相当于be willing to）
C.If you would kindly wait a moment,I'll see what I can do.(这里的would还是表示“意愿”,常用于客气的请求,这时,主句动词既可用will/shall,也可用would/should/could/might；如果表意愿的would不是用于客气请求,那么在一定上下文中也可能表示不大可能实现的“意愿”,这就属于非真实条件句,即第三种类型）
3）“替换形式”,两种：
A.Set ur alarm clock,and you won't oversleep.=If you set...,you won't...
B.Set ur alarm clock,or(else)you'll oversleep.=If you don't set...,you'll...
第三种类型：
是非真实条件句的一种,If I came into a fortune,I would give up working.
第四种类型：
表示与过去事实相反的非真实条件句,We would/coul/might have called you if we had known your phone number.
你说的主将从现只是第二种的最最基本的一种,清楚多了吧