Volume 2 Chapter 8 Quest Sub-menu QUESTION LOGIC

Function

QUESTION LOGIC is concerned with how to compose a search query in terms of:

the tests Tn
the logical operators .AND. .OR. .NOT.
and optionally one level of parentheses

Remarks

Before considering how to compose the search question in the QUEST sub-menu it will be helpful to discuss how the program handles the search question.

The search question will be executed after any SCREEN instructions and only if the SCREEN tests succeed.
The logical operators .AND. .OR. .NOT. can be replaced by the symbols + , - respectively.
If parentheses are used then:
- only one level of parentheses is allowed
- every test Tn or group of tests must be enclosed by parentheses.
A search question with one test requires neither logical operators nor parentheses, eg. QUES T1
Note, however, that the following two instructions are equivalent:
- QUES .AND. T1
- QUES (T1)
Two or more tests may be combined with the logical operators, for example:
- QUES T1 .AND. T2
- QUES T1 .AND. T2 .OR. T3
- QUES T1 .NOT. T4 .AND. T2
The search program will evaluate such logical expressions according to the order of precedence:
- .NOT. first
- .AND. second
- .OR. third
Operators of equal rank will be evaluated from left to right.
Unnecessary tests will never be performed and this means that care should be taken to ensure that the most efficiently executed tests are executed first.
Consider QUES (T1 .OR. T2) .AND. (T3)
T1 will be tested first. If it succeeds T2 will not be executed and the program will skip to test T3.
If T1 and T2 both fail then T3 will not be executed.
A suggested order of tests to achieve maximum efficiency is:
1. Bit screen tests *BTEST
2. Numeric tests
3. Text tests
4. Connectivity tests

If in doubt regarding the logical combination of tests it is safest to use parentheses.

Thus:

QUES (T1) .AND. (T2 .OR. T3)

is equivalent to:

QUES T1 .AND. T2 .OR. T3

and

QUES (.NOT.T4) .AND. (T1 .AND. T2)

is equivalent to:

QUES T1 .NOT. T4 .AND. T2

Graphics QUEST3D Procedure

Having defined tests Tn selection of the command QUEST in the BUILD or SEARCH menus will display the QUEST sub-menu.

The tests are displayed, each in a box, in the diagram area of the screen.

In the top right-hand corner of the menu are the logical operators and parentheses to be used for construction of the search question.

The logical operator .AND. is the default, as indicated by the red box surrounding it.

In the dialogue area there is:

The current QUEST line is:
QUEST
Please select a test or a logical operator. Select "START-SEARCH" to begin.

Suppose 3 tests have been defined. A few examples will illustrate how to compose the QUEST line:

Ex.1

 QUES T  T1  .AND.  T2

Ex.2

 QUES T  T1.  OR.  T2

Ex.3

 QUES T  (T1)  .AND.  (T2  .OR.  T3)

      ACTION      ACTIVE OPERATOR   CONTENTS OF QUESTION LINE
Ex.1
                    .AND.           QUEST
      Select  T1    .AND.           QUEST  T1
      Select  T2    .AND.           QUEST  T1  .AND.  T2
Ex.2
                    .AND.           QUEST
      Select  T1    .AND.           QUEST  T1
      Select .OR.   .OR.            QUEST  T1
      Select  T2    .OR.            QUEST  T1  .OR.  T2
Ex.3
                    .AND.           QUEST
      Select  (     .AND.           QUEST  (
      Select  T1    .AND.           QUEST  (T1
      Select  )     .AND.           QUEST  (T1)
      Select  (     .AND.           QUEST  (T1)  .AND.  (
      Select  T2    .AND.           QUEST  (T1)  .AND.  (T2
      Select .OR.   .OR.            QUEST  (T1)  .AND.  (T2
      Select  T3    .OR.            QUEST  (T1)  .AND.  (T2  .OR.  T3
      Select  )     .OR.            QUEST  (T1)  .AND.  (T2  .OR.  T3)

As indicated above, once the search question has been correctly composed the search can be initiated by selecting START-SEARCH.

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Volume 2 Chapter 8 Quest Sub-menu REBUILD-FRAG .