有关动词不定式的问题they are an artistic pleasure(艺术的享受) to look at.这句话的解释该不定式在句中是什么成分?那they are restful to talk to.呢不定式在句中作什么成分？

动词不定式概述
一 不定式的体
1. 不定式的一般式(to do)表示不定式的.动作将要发生或与谓语动作同时发生.
2 不定式的进行体(to be doing)表示不定式的动作正在发生.
不定式的完成体(to have done)表示不定式的动作在谓语动作之前发生.
二 不定式的逻辑主语
1 不定式的逻辑主语常不出现在句中.
2 句子的主语,宾语有时是不定式的逻辑主语.
3 不定式前"for+名词/代词"结构中的名词或代词也可以用来表示不定式的;逻辑主语.
4 在"It+be+形容词+of+名词/代词+to do"结构中,名词或代词为不定式的逻辑主语.该结构中的形容词通常用来表示人的品质.例如:kind, good, nice, bad, cruel, honest, bold, thoughtful, right, wrong, wise, clever, silly, foolish, careless, rude等.
例如:It's very kind of you to cal to tell me about the conference.
三 不定式的否定式
不定式否定式由not/never +to do构成
四 不定式的句法功能
1 不定式做主语
1)To say something is one thing; to do it is another.
2)It is not a good idea to build houses along the lines where two of the earth's plates join together.
注:充当主语的不定式即可置于句首,位于谓语动词之前,也可作为句子的真正主语置于句末,用作形式主语.
2 不定式作表语
3)Her uncle seems to be acting rather strangely towards her these days.
4)The purpose of the fence is to keep out a type of wild dog called a "Dingo".
5)One suggested answer is for farmers to limit the number of their cattle.
注:充当表语的不定式一般位于be ,seem等系动词后.
3 不定式作宾语
6)Shylock agreed to lend Antonio money on one condition.
注:充当宾语的不定式位于及物动词后.常用不定式作宾语的动词有:agree, plan, determine, dare, refuse, hope, wish, expect, promise, choose, pretend, decide, manage, intend, offer, afford, demand.
7)The dusty air makes it difficult to get a clear picture of space.
注:充当宾语的不定式如果有自己的表语,则可用代替只个不定式作为形式宾语,而作为真正宾语的不定式则放在表语之后.以it作为形式宾语的这种结构常用在think, feel, find, make, consider等动词之后.
big and strong.
4 不定式作宾语补足语
8)The powder made from fish, blood and bones will make the cabbage plants grow big and strong.
9)Portia told Bassanio to go to his friend at once.
注:在下列动词后作宾语补足语的不定式通常不带to.这些动词是observe, notice, see, hear, watch, have, feel, make, let.但上述动词转换为被动语态时,其后的不定式须带to.例如:The cabbage plants will be made to grow
动词不定式(todo)是初中英语课的一个重点，也是中考要考查的一个项目。动词不定式属于非谓语动词的一种形式，很多同学经常把它和谓语动词混在一起，掌握起来有困难。下面我们对动词不定式的用法做简单归纳，帮助同学们记忆：

to look at.----------作后置定语

后置定语,修饰an artist pleasure

定语
动词不定式作定语后置修饰前面的名词 an artistic pleasure