Bronze Edition Guide - True BASIC

212 BRONZE Edition Guide
sequence, options$. If you use typed commands, anything you type following the do
command itself and a comma will be similarly assigned. (For the typed command, you’ll
automatically use the TBDo directory; see the discussion of aliases in Chapter 15.)
Here is a simple example: Suppose you want a do program that will change all upper
case letters into lowercase, or all lower case letters into uppercase. Write the following
subroutine:
EXTERNAL
SUB xxxxx (current$(), options$)
LET options$ = ltrim$(lcase$(options$))[1:1]
FOR i = 1 to ubound(current$())
IF options$ = “u” then
LET current$(i) = ucase$(current$(i))
ELSE IF options$ = “l” then
LET current$(i) = lcase$(current$(i))
ELSE
PRINT “Use either ‘upper’ or ‘lower’”
EXIT SUB
END IF
NEXT i
END SUB
Now save it with the name “ChangeCase” in the directory TBDo.
To use your new DO program to change all uppercase letters to lowercase in your current
program, type the command
do changecase, lower
Conversely, if you want to change to all uppercase, type the command
do changecase, upper
That’s all there is to it.
If you put your very own DO program in the directory (folder) TBDo, its name will
appear in the Run menu the next time you start True BASIC. If you put it into a different
directory, you can access it by selecting “Do ...” from the Run menu, using the Finder
to locate it, and then clicking on “Open”. In any case, you will be asked if there are any
command-line parameters; whatever you enter will be supplied as the value of options$
in the call to the DO program.