Language Guide

CHAPTER 5

Objects and References

Using the Filter Reference Form 141

For example, compare this reference without a ﬁlter

every word of paragraph 5

to the same reference with a ﬁlter:

every word of paragraph 5 where character 1 = "M"

The ﬁrst reference speciﬁes all the words in the ﬁfth paragraph. The second

reference, which includes the ﬁlter where character 1 = "M", speciﬁes all

the words in the same container whose ﬁrst character is “M”. Words that do

not pass this test are ﬁltered out.

In effect, a ﬁlter reduces the number of objects in the container. Instead of

specifying every word of the ﬁfth paragraph, the reference

every word of paragraph 5 whose first character = "M"

speciﬁes every word of a smaller container, the words of the ﬁfth paragraph

whose ﬁrst characters are “M”. Similarly,

words 1 thru 5 of paragraph 5 whose first character = "M"

speciﬁes the ﬁrst ﬁve words of the same smaller container.

To determine the objects in the smaller container, the application applies the

ﬁlter to all of the objects of the speciﬁed class in the speciﬁed container—in this

case, the words in the ﬁfth paragraph. The application uses the ﬁlter to test

each object in turn, starting with the ﬁrst.

Within a ﬁlter, the predeﬁned variable it refers to the object currently being

tested. For example, in the reference

second paragraph of document "Product Intro" 

where it contains "dynamo"

the word it refers to each paragraph in the document Product Intro. The

ﬁlter, contains "dynamo", is applied to each paragraph in the document,

resulting in a smaller container whose paragraphs all contain the string

"dynamo". The reference specifies the second paragraph of that smaller

container.