Tag Archives: RECNO()

-> Alias assignment

Posted on by vivaclipper 
->
 Alias assignment--binary                        (Special)
------------------------------------------------------------------------------
 Syntax

     <idAlias>-><idField>
     <idAlias>->(<exp>)
     (<nWorkArea>)-><idField>
     (<nWorkArea>)->(<exp>)
     FIELD-><idVar>
     MEMVAR-><idVar>

 Operands

     <idAlias> is the name of the unselected work area to access and must
     refer to a work area with a database file in USE.

     <nWorkArea> is the number of the unselected work area to access.

     <idField> is the name of a field in the specified work area.

     <exp> is an expression of any data type to be executed in the
     specified work area.  If an expression more complicated than a single
     field reference is used as the second operand, the expression must be
     enclosed in parentheses ( ).

     <idVar> is any valid CA-Clipper identifier.  Depending on whether
     you specify FIELD or MEMVAR, the identifier will be forced to a database
     field or memory variable (public or private) reference.

 Description

 When used with an <idAlias> as the first operand, the alias operator

     (->) accesses field information or evaluates an expression in the
     indicated work area.  The alias operator implicitly SELECTs the
     <idAlias> before evaluating the <idField> or <exp> operand.  When the
     evaluation is complete, the original work area is SELECTed again.  An
     alias reference can be in an expression or on a line by itself:

     ? Customer->Name
     Customer->(UpdateTransaction())

     Using the alias operator lets you:

     .  Access information from unselected work areas within
        expressions

     .  Access environmental information from unselected work areas

     .  Access information from unselected work areas in modes such as
        REPORT and LABEL FORMs

     .  Write more compact code

     In addition to allowing expression and field evaluation in unselected
     work areas, the alias operator makes an explicit reference to a field or
     variable using either the FIELD or the MEMVAR keyword aliases.  MEMVAR
     forces <idVar> to refer to a memory variable name, and FIELD forces it
     to reference a database field.  These special alias identifiers allow
     you to avoid ambiguity when there are conflicts between field and memory
     variable names.  Remember that a reference to a variable identifier not
     prefaced with an alias defaults to a field if there are both field and
     memory variables with the same name.  To override this, use the (/V)
     option when compiling.

     In addition to specifying the alias as an identifier, you can access the
     target work area using an expression that returns the work area number
     if the expression is enclosed by parentheses.  This lets you use work
     area numbers as handles, which is useful for passing references to work
     areas without using macros, aliases, names, etc.

 Examples

     .  This example accesses database and work area information in an
        unselected work area:

        USE Customer NEW
        USE Invoices NEW
        ? Customer->CustName                  // Result: Bill Smith
        ? Customer->(RECNO())                 // Result: 1
        ? Customer->(FOUND())                 // Result: .F.
        ? Customer->(City + ", " + State + ;
           "  " + Zip)                        // Result: ShadowVille,
                                              //         CA  90415

     .  This example uses a user-defined function (MySeek()) as an
        operand of the alias operator for a common operation that normally
        requires many more statements:

        IF Invoices->(MySeek(CustNum))
           <process customer>...
        ELSE
           <process no find>...
        ENDIF
        RETURN

        FUNCTION MySeek( cSearch )
           SEEK cSearch
        RETURN (FOUND())

        Note:  This example is just an illustration of the alias operator
        with a user-defined function.  CA-Clipper's DBSEEK() could be used
        instead of MySeek().

     .  This example explicitly references field and memory variables
        with the same name:

        USE Customer NEW
        MEMVAR->CustName = "Bill Smith"      // Create a memvar
                                             // CustName
        LOCATE FOR MEMVAR->CustName = FIELD->CustName

     .  This example uses an expression as a work area handle to
        create a work area-independent database operation:

        cTable1 := "C:Myfile.dbf"
        cTable2 := "D:Myfile.dbf"
        USE (cTable1) NEW
        hArea1 = SELECT()
        USE (cTable2) NEW
        hArea2 = SELECT()
        DoStuff( hArea1, hArea2 )

        FUNCTION DoStuff( hArea1, hArea2 )
           LOCAL nCount, nSave
           nSave := SELECT()
           SELECT (hArea1)
           FOR nCount := 1 TO FCOUNT()
              FIELDPUT( nCount, ( hArea2 )-> ;
                 ( FIELDGET( nCount )))
           NEXT
           SELECT (nSave)
           RETURN NIL

See Also: FIELD FIELDNAME() FIELDPOS() FIELDGET() SELECT

Simple Clipper Extensions

Posted on by vivaclipper

Simple extensions

Exact comparisons,
Name precedence,
SELECT 0,
Alias functions,
Call by reference and value,
Other Clipper extensions

C5 Database Functions

Posted on by vivaclipper

AFIELDS() :

Fill arrays with the structure of the current database file

AFIELDS([<aFieldNames>],
    [<aTypes>],
    [<aWidths>],
    [<aDecimals>]) --> nFields

ALIAS() : 

Return a specified work area alias

ALIAS([<nWorkArea>]) --> cAlias

BOF() : 

Determine when beginning of file is encountered

BOF() --> lBoundary

DBAPPEND() : 

Add a new record

DBAPPEND() --> NIL

DBCLEARFILTER() : 

Clear a filter condition

    DBCLEARFILTER() –> NIL

DBCLEARIND() :  Close all indexes for the current work area

    DBCLEARINDEX() --> NIL

DBCLEARREL() : 

Clear active relations

DBCLEARRELATION() --> NIL

DBCLOSEALL() : 

Close all occupied workareas

DBCLOSEALL() --> NIL

DBCLOSEAREA() : 

Close a workarea

DBCLOSEAREA() --> NIL

DBCOMMIT() : 

Flush pending updates

DBCOMMIT() --> NIL

DBCOMMITALL() : 

Flush pending updates in all workareas

DBCOMMITALL() --> NIL

DBCREATE() : 

Create a database file from a database structure array

DBCREATE(<cDatabase>, <aStruct> [, <cDriver> ] ) --> NIL

DBCREATEIND() : 

Create an Index

   DBCREATEINDEX(<cIndexName>, <cKeyExpr>,
        [<bKeyExpr>], [<lUnique>]) --> NIL

DBDELETE() : 

Mark a record for deletion

DBDELETE() --> NIL

DBEDIT() : 

        Browse records in a table layout

    DBEDIT([<nTop>], [<nLeft>],
        [<nBottom>], <nRight>],
        [<acColumns>],
        [<cUserFunction>],
        [<acColumnSayPictures> | <cColumnSayPicture>],
        [<acColumnHeaders> | <cColumnHeader>],
        [<acHeadingSeparators> | <cHeadingSeparator>],
        [<acColumnSeparators> | <cColumnSeparator>],
        [<acFootingSeparators> | <cFootingSeparator>],
        [<acColumnFootings> | <cColumnFooting>]) --> NIL

DBEVAL() : 

Evaluate a code block for each record

DBEVAL(<bBlock>,
    [<bForCondition>],
    [<bWhileCondition>],
    [<nNextRecords>],
    [<nRecord>],
    [<lRest>]) --> NIL

DBF()* : 

Return current alias name

DBF() --> cAlias

DBFIELDINFO() : 

Return and optionally change information about a field

   DBFIELDINFO(<nInfoType>,

        <nFieldPos>,
        [<expNewSetting>]) --> uCurrentSetting

DBFILEGET() : 

Insert the contents of a field into a file

     DBFILEGET(<nFieldPos>, <cTargetFile>, <nMode>)
        --> lSuccess

DBFILEPUT() : 

Insert the contents of a file into a field

     DBFILEPUT(<nFieldPos>, <cSourceFile>)
        --> lSuccess

 DBFILTER() : 

Return the current filter expression as a character string

DBFILTER() --> cFilter

DBGOBOTTOM() : 

Move to the last logical record

DBGOBOTTOM() --> NIL

DBGOTO() : 

Move to a particular record

DBGOTO(<nRecordNumber>) --> NIL

DBGOTOP() : 

Move to the first logical record

DBGOTOP() --> NIL

DBINFO() : 

         Return and optionally change database file information

    DBINFO(<nInfoType>, [<expNewSetting>])
        --> uCurrentSetting

DBORDERINFO() :          Return and optionally change information about orders and index files

    DBORDERINFO(<nInfoType>,   [<cIndexFile>],
        [<cOrder> | <nPosition>],
        [<expNewSetting>]) --> uCurrentSetting

DBRECALL() : 

Reinstate a record marked for deletion

DBRECALL() --> NIL

DBRECORDINFO() :

         Return and optionally change information about a record

    DBRECORDINFO(<nInfoType>,
        [<nRecord>],
        [<expNewSetting>]) --> uCurrentSetting

DBREINDEX() :

         Recreate all active indexes for the current work area

    DBREINDEX() --> NIL

DBRELATION() :

Return the linking expression of a specified relation

DBRELATION( <nRelation> ) --> cLinkExp

DBRLOCK() :      

         Lock the record at the current or specified identity

    DBRLOCK([<xIdentity>]) --> lSuccess

DBRLOCKLIST()          Return an array of the current lock list

   DBRLOCKLIST() --> aRecordLocks

DBRSELECT() :

Return the target workarea number of a relation

DBRSELECT( <nRelation> ) --> nWorkArea

DBRUNLOCK()    

          Release all or specified record locks

    DBRUNLOCK([<xIdentity>]) --> NIL

DBSEEK() : 

Search for a key value

DBSEEK(<expKey>, [<lSoftSeek>]) --> lFound

DBSELECTAR() : 

Change the current workarea

DBSELECTAREA(<nArea> | <cAlias>) --> NIL

DBSETDRIVER() : 

Set the default database driver

DBSETDRIVER([<cDriver>]) --> cCurrentDriver

DBSETFILTER() : 

Set a filter condition

DBSETFILTER(<bCondition>, [<cCondition>]) --> NIL

DBSETINDEX()    

         Empty orders from an order bag into the order list

    DBSETINDEX(<cOrderBagName>) --> NIL

DBSETORDER()

Set the controlling order

    DBSETORDER(<nOrderNum>) --> NIL

DBSETRELAT() :

Relate two workareas

DBSETRELATION( <nArea> | <cAlias>, <bExpr>, [<cExpr>]) --> NIL

DBSKIP() : 

Move relative to the current record

DBSKIP([<nRecords>]) --> NIL

DBSTRUCT() : 

Create an array containing the structure of a database file

DBSTRUCT() --> aStruct

DBUNLOCK()

Release all locks for the current work area

    DBUNLOCK() --> NIL

DBUNLOCKALL()

Release all locks for all work areas

    DBUNLOCKALL() --> NIL

DBUSEAREA() : 

Use a database file in a workarea

DBUSEAREA( [<lNewArea>],
    [<cDriver>],
    <cName>,
    [<xcAlias>],
    [<lShared>],
    [<lReadonly>]) --> NIL

DELETED() : 

Return the deleted status of the current record

DELETED() --> lDeleted

EOF() : 

Determine when end of file is encountered

EOF() --> lBoundary

FCOUNT() : 

Return the number of fields in the current (.dbf) file

FCOUNT() --> nFields

FIELD() : 

Return a field name from the current (.dbf) file

    FIELD/FIELD(<nPosition>) --> cFieldName

FIELDBLOCK() :

Return a set-get code block for a field variable

FIELDBLOCK(<cFieldName>) --> bFieldBlock

FIELDGET() : 

Retrieve the value of a field using the ordinal position of the field in the database structure

FIELDGET(<nField>) --> ValueField

FIELDNAME() : 

Return a field name from the current (.dbf) file

FIELDNAME/FIELD(<nPosition>) --> cFieldName

FIELDPOS() : 

Return the position of a field in a workarea

FIELDPOS(<cFieldName>) --> nFieldPos

FIELDPUT() : 

Set the value of a field variable using the ordinal position of the field in the database structure

FIELDPUT(<nField>, <expAssign>) --> ValueAssigned

FIELDWBLOCK() : 

Return a set-get block for a field in a given workarea

FIELDWBLOCK(<cFieldName>, <nWorkArea>) --> bFieldWBlock

FLOCK() : 

Lock an open and shared database file

    FLOCK() –> lSuccess

FOUND() : 

Determine if the previous search operation succeeded

FOUND() --> lSuccess

HEADER() : 

Return the current database file header length

HEADER() --> nBytes

LASTREC() : 

Determine the number of records in the current (.dbf) file

LASTREC() | RECCOUNT()* --> nRecords

LUPDATE() : 

Return the last modification date of a (.dbf) file

LUPDATE() --> dModification

RECCOUNT()* : 

Determine the number of records in the current (.dbf) file

RECCOUNT()* | LASTREC() --> nRecords

RECNO() : 

Return the current record number of a work area

RECNO() --> nRecord

RECSIZE() : 

Determine the record length of a database (.dbf) file

RECSIZE() --> nBytes

RLOCK()

Lock the current record in the active work area

    RLOCK() --> lSuccess

SELECT() : 

Determine the work area number of a specified alias

SELECT([<cAlias>]) --> nWorkArea

USED() : 

Determine if a database file is in USE

USED() --> lDbfOpen