Q31557: Passing Array of TYPE or Fixed-Length Strings to SUBprogram

Article: Q31557
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 15-JAN-1991

An array of fixed-length strings cannot be passed directly as a
parameter to a SUBprogram or FUNCTION procedure (that is, the phrase
AS STRING*n cannot be used in DECLARE, SUB, or FUNCTION statements).

The following are three alternatives for passing an array of
fixed-length strings to a procedure:

1. Pass the array of fixed-length strings through COMMON SHARED.
   (Please see Example 1 below.)

2. Convert the array of fixed-length strings to an array of
   user-defined type and pass the array AS that type. (Please see
   Example 2 below or the TORUS.BAS sample program provided on the
   release disk.)

3. Convert the array of fixed-length strings to an array of
   user-defined type and pass that array through COMMON SHARED. (Please
   see Example 3 below.)

This information applies to QuickBASIC Versions 4.00, 4.00b and 4.50,
to Microsoft BASIC Compiler Versions 6.00 and 6.00b for MS-DOS and
OS/2, and to Microsoft BASIC Professional Development System (PDS)
Versions 7.00 and 7.10 for MS-DOS and MS OS/2.

Note that when you pass a simple fixed-length string variable to a
procedure, it is always converted to a variable-length string. Thus,
the variable-length STRING type is allowed in DECLARE, SUB, and
FUNCTION statements, but the fixed-length STRING*n type is not.

The following is an example (Example 1) of how to pass an array of
fixed-length strings through COMMON SHARED:

   DECLARE SUB TEST()
   DIM X(1 TO 30) AS STRING*22
   COMMON SHARED X() AS STRING*22
   X(5)="THIS IS A TEST"
   CALL TEST
   END
   SUB TEST STATIC
      PRINT X(5)
   END SUB

The following is an example (Example 2) of how to pass an array of
user-defined type as a parameter to a procedure:

   DECLARE SUB sub1 (t() AS ANY)
   TYPE foo
     y AS STRING * 10
   END TYPE
   DIM t(10) AS foo
   CALL sub1(t())
   PRINT t(1).y
   END
   SUB sub1 (t() AS foo)
     t(1).y = "test"
   END SUB

The following is an example of how to pass an array of user-defined
type through COMMON SHARED:

   TYPE FOO
     FIRST AS STRING*25
   END TYPE
   DIM AR(9) AS FOO
   COMMON SHARED AR() AS FOO, TEMP AS INTEGER
   AR(5).FIRST="This is fifth element"
   TEMP=99
   CALL TEST
   END
   SUB TEST STATIC
     PRINT AR(5).FIRST
     PRINT TEMP
   END SUB

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