Microsoft KB Archive/113172

{| = How the EVALUATE Function Works =
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ID: Q113172

The information in this article applies to:


 * Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a, and 2.5b
 * Microsoft FoxPro for Windows, versions 2.5, 2.5a, and 2.5b
 * Microsoft FoxPro for Macintosh, version 2.5b

SUMMARY
The EVALUATE function evaluates the expression contained within the parentheses and returns the result. However, the EVALUATE function produces different results based on the exact syntax of the statement.

MORE INFORMATION
The EVALUATE function returns different values based on whether quotation marks ("") are placed around the expression being evaluated. Enclosing the expression within quotation marks causes EVALUATE to return the literal value of the expression. However, if no quotation marks are used, the command returns the value stored in the expression.

To demonstrate this behavior, type the following in the Command window:

x = "Level1" Level1 = "Level2" ? EVALUATE("X")   && "Level1" appears on the screen ? EVALUATE(X)     && "Level2" appears on the screen. As you can see, quotation marks determine what value the EVALUATE function returns. With the quotation marks, EVALUATE returns the literal value of the expression; in this case, "Level1". Without the quotation marks, EVALUATE returns the value contained within the expression being evaluated; in this case, "Level2". Since the function returns quite different values based on its syntax, it may cause various error messages to appear, depending on the program's code. For example, the following code returns the error "Index Does Not Match Database File. Recreate Index":

IF _MAC USE tutorial\customer SHARE ELSE USE c:\ \tutorial\customer.dbf SHARE ENDIF BROWSE NOWAIT PUBLIC ord ord="Company" INDEX ON EVALUATE(ord) TO test.idx APPEND BLANK REPLACE Company WITH 'test company"  SHOW WINDOW CUSTOMER REFRESH Since the EVALUATE function in this example does not contain quotation marks around the variable "ord", the literal value "company" is not returned. Instead, EVALUATE(ord) returns the value of the COMPANY field of the current record, which causes the error messages.