Reduce subroutine
Description
Creates a cursor using a filter or applies a filter to an existing cursor.
Syntax
Reduce(reduce_script, sort_list, mode, table_name, cursorvar, flag)
Parameters
The Reduce subroutine has the following parameters.
| Parameter | Description |
|---|---|
| reduce_script | Used to pass an expression containing the formatted reduction criteria. The information passed in reduce_script must be formatted as follows. · All column names must be enclosed in braces { }. · Column names must not have spaces in them. · All constants must be on the right side of the comparison operator and must be enclosed in either single or double quotes. · All comparison operators must be reduced to the primitive set of operators and must be separated by spaces. Operator - Primitive Between - Between Equal to - EQ Less than - LT Greater than - GT Less than or equal to - LE Greater than or equal to - GE Not - Not Starting with - ] Ending with - [ Containing - [ ] Matches - Match Range - From To Sunday - Sun Monday - Mon Tuesday - Tue Wednesday - Wed Thursday - Thu Friday - Fri Saturday - Sat Today - Today Yesterday - Yst Tomorrow - Tom Next - Next Last - Last Example Assignments for reduce_script: reduce_script = "WITH NOT {DATE} EQ '9-23-59'" reduce_script = "WITH {CITY} EQ 'Boston' OR WITH {STATE} EQ 'CA'" reduce_script = 'WITH {GRADE_POINT} FROM "2.0" TO "4.0"' reduce_script = 'WITH {MAJOR} EQ ': Quote(major_var) reduce_script := ' AND WITH {MINOR} EQ ' : Quote(minor_var) reduce_script = 'WITH {INV_DATE} LT ' : Quote(Date() - 30) reduce_script := ' OR WITH {invoice_amt} GE "1000"' reduce_script = 'WITH {PHONE} Match "3N-4N"' |
| Sort_list | Pass the sort criteria in sort_list. The sort criteria requires the same format as when used in Select … By. If the program intends to sort, both the call to Reduce and the Select statement must use the same sort_list. Example assignments for sort_list: sort_list = "CITY" sort_list = "ST" : @FM : "city" sort_list = "#INV_TOTAL" sort_list = "ST" : @FM : "#INV_TOTAL" |
| Mode | Used to pass one of three values: Value - Description 0 - Indicates that these are new reduction criteria for an existing cursor. 1 - Indicates that the subroutine should return the results of the reduction in the next available cursor. 2 - Indicates that these are additional criteria for an existing cursor. The new criteria will be joined with a logical And to any previous criteria. |
| table_name | Used to pass the name of the table to be searched. |
| cursorvar | Used to pass a cursor already initialized (Modes 0 and 2) or a cursor to be initialized (Mode 1). |
| flag | Returns true if the subroutine was successful and false if unsuccessful. |
See Also
Example
Function Reduce_Example(param1)
* The following code provides reduction criteria to a selection of keys
* from CUSTOMERS using Select...By.
Declare Subroutine Reduce, Msg, FsMsg
$Insert Logical
Equ new_exist$ To 0 ; * Reduce Mode 0
Equ next_cur$ To 1
Equ add_exist$ to 2
table_name = "CUSTOMERS"
flag = ""
done = False$
CursorVar = ""
* Clears all cursors
For counter = 0 To 8
ClearSelect counter
Next counter
sort_list = "STATE"
Reduce_Script = "WITH {STATE} EQ 'NY' OR WITH {STATE} EQ 'CA'"
mode = NEXT_CUR$
Reduce(reduce_script, sort_list, mode, table_name, Cursorvar, flag)
If flag then
Select table_name By sort_list Using Cursorvar then
Open table_name To file_var then
ctr = 0
Loop
ReadNext key Using Cursorvar By AT Else done = TRUE$
Until done
Read rec From file_var, key then
Gosub Processing
end
Repeat
End Else
FsMsg()
End
End Else
FsMsg()
end
End Else
FsMsg()
End
Return ctr
Processing:
ctr += 1
return