ALTER

Syntax ALTER ‘variable’ TO value
Location ALTER (DIY Toolkit - Vol U)

This command works alongside SET from the same toolkit and allows you to re-define the universal constants created with SET.

Unlike SET, the constant to be re-defined must appear in quotes as the first parameter (otherwise the value of the constant is passed to be altered by the command!!). As with SET, the constant and the value must be of the same type, otherwise an ‘error in expression’ will be reported.

If the constant has not previously been defined with SET, then if it is recognised for some other reason an ‘In Use’ error will be reported. If it is not recognised at all, then ‘Not Found’ will be reported.

Unlike SET, you can use ALTER from any program which is being used on the QL and therefore you can use this to update constants or possibly device names (or anything else you can invent).

Example

Set the following from SuperBASIC:

10 SET DEF_DRIVE$ TO ‘flp1_’

If whilst using another program, the user re-defines the default device, that program can use a line such as: ALTER ‘DEF_DRIVE$’ TO ‘win1_prog_’ which will then alter the default device for all programs which read this constant.

NOTE

ALTER does not work on SMS.

CROSS-REFERENCE

See SET.