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AEVAL()
Execute a code block for each element in an array
------------------------------------------------------------------------------
Syntax
AEVAL(<aArray>, <bBlock>,
[<nStart>], [<nCount>]) --> aArray
Arguments
<aArray> is the array to traverse.
<bBlock> is a code block to execute for each element encountered.
<nStart> is the starting element. If not specified, the default is
element one.
<nCount> is the number of elements to process from <nStart>. If not
specified, the default is all elements to the end of the array.
Returns
AEVAL() returns a reference to <aArray>.
Description
AEVAL() is an array function that evaluates a code block once for each
element of an array, passing the element value and the element index as
block parameters. The return value of the block is ignored. All
elements in <aArray> are processed unless either the <nStart> or the
<nCount> argument is specified.
AEVAL() makes no assumptions about the contents of the array elements it
is passing to the block. It is assumed that the supplied block knows
what type of data will be in each element.
AEVAL() is similar to DBEVAL() which applies a block to each record of a
database file. Like DBEVAL(), AEVAL() can be used as a primitive for
the construction of iteration commands for both simple and complex array
structures.
Refer to the Code Blocks section in the "Basic Concepts" chapter of the
Programming and Utilities Guide for more information on the theory and
syntax of code blocks.
Examples
. This example uses AEVAL() to display an array of file names
and file sizes returned from the DIRECTORY() function:
#include "Directry.ch"
//
LOCAL aFiles := DIRECTORY("*.dbf"), nTotal := 0
AEVAL(aFiles,;
{ | aDbfFile |;
QOUT(PADR(aDbfFile[F_NAME], 10), aDbfFile[F_SIZE]),;
nTotal += aDbfFile[F_SIZE]);
} )
//
?
? "Total Bytes:", nTotal
. This example uses AEVAL() to build a list consisting of
selected items from a multidimensional array:
#include "Directry.ch"
//
LOCAL aFiles := DIRECTORY("*.dbf"), aNames := {}
AEVAL(aFiles,;
{ | file | AADD(aNames, file[F_NAME]) };
)
. This example changes the contents of the array element
depending on a condition. Notice the use of the codeblock
parameters:
LOCAL aArray[6]
AFILL(aArray,"old")
AEVAL(aArray,;
{|cValue,nIndex| IF(cValue == "old",;
aArray[nIndex] := "new",)})
Files Library is CLIPPER.LIB.
