不知网友说的“前置限制”是何意思？单个的现在分词作定语，一般都置于被修饰词之前。

现在分词作定语，说明被修饰语和现在分词是“主谓关系”。既如此，就可以扩展为一个定语从句，该定语从句为主动语态，而多为进行时态。例如：

a sleeping baby → a baby who is sleeping.

a barking dog→ a dog that is barking

flying birds → birds that are flying

smiling faces →faces that are smiling

a floating boat → a boat that is floating

falling leaves → leaves that are falling

boiling water → water that is boiling

the setting sun → the sun that is setting

the rising sun → the sun that is rising

the coming week → the week that will come

the following questions→ the questions that follow

running water → water that is running

a developing country→ a country that is developing

the suffering people → people who are suffering

a missing child→ a child who is missing

现在分词短语作定语，都是置于被修饰语之后。单个的现在分词作定语跟动名词作定语，一般都置于被修饰词之前。

解答如下：

现在分词作定语可以改为一个进行时态/一般时态定语从句作定语。

crying children 在哭的孩子

=The children who are crying

screaming children 在尖叫的孩子

=the children who are screaming

working children 在工作的孩子

=the children who are working

laughing children 在笑的孩子

=the children who are laughing

moving children 在移动的孩子

=the children who are moving

备注(1)：动态动词的现在分词作定语既表示进行由表示主动,可以改为进行时态定语从句作后置定语。

The boy watching TV in the room is Tom

=The boy who is watching TV in the room is Tom

备注(2)静态动词现在分词作定语只表示主动，可以改为一般时的定语从句作后置定语。

The  house facing south is mine

=The house which faces south is mine