@...CLEAR
 Clear a rectangular region of the screen
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 Syntax

     @ <nTop>, <nLeft> [CLEAR
        [TO <nBottom>, <nRight>]]
        [DOUBLE] [COLOR <cColor>]

 Arguments

     <nTop> and <nLeft> define the upper-left corner coordinate.

     TO <nBottom>, <nRight> defines the lower-right corner
     coordinates of the screen region to CLEAR.  If the TO clause is not
     specified, these coordinates default to MAXROW() and MAXCOL().

 Description

     @...CLEAR erases a rectangular region of the screen by filling the
     specified region with space characters using the current standard color
     setting.  After @...CLEAR erases the designated region, the cursor is
     located in the upper corner of the region at <nTop> + 1 and <nLeft> + 1.
     ROW() and COL() are also updated to reflect the new cursor position.

 Examples

     .  This example erases the screen from 10, 10 to 20, 40, painting
        the region blue and then displaying a bright cyan box on blue:

        SETCOLOR("BG+/B")
        @ 10, 10 CLEAR TO 20, 40
        @ 10, 10 TO 20, 40

 Files   Library is CLIPPER.LIB.