How the EVALUATE() Function Works

• 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.

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:\<foxpro directory>\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

REFERENCES

"Commands & Functions," version 2.0 (MS-DOS), page C3-356 "Language Reference," version 2.5 (MS-DOS and Windows), page L3-485 "Language Reference," version 2.5 (Macintosh), page 407