Bronze Edition Guide - True BASIC

226 BRONZE Edition Guide
Here’s another example that changes all letters in a file to lowercase:
DIM line$(1000)
OPEN #3: NAME “Program5.Tru”
LET i = 0
DO WHILE MORE #3 ! Read lines into array
LET i = i + 1
LINE INPUT #3: line$(i)
LOOP
ERASE #3
! Erase the file
FOR j = 1 to i
! Rewrite in lowercase
PRINT #3: Lcase$(line$(j))
NEXT j
END
The program reads the file into an array, erases the file, and then writes lowercase versions
of the lines back into the file.
A word of caution about using the MAT PRINT and MAT INPUT statements with text files:
while both work with text files, the MAT PRINT statement does not write information in a
format that will work with the MAT INPUT statement. The MAT INPUT statement
expects items of a row to be separated by commas, but the MAT PRINT statement separates
the items of a row by spaces. There are two ways to solve this problem:
(1) Create the file’s contents by printing individual elements, putting a comma after each
item except the last:
...
FOR i = 1 to Ubound(array) - 1
PRINT #7: array(i); “, “;
NEXT i
PRINT array(Ubound(array))
...
(2) Use the LINE INPUT statement to input an entire line from the file and then “parse”
the line into its component items using the ExplodeN subroutine provided in the Str-
Lib library.
LIBRARY “C:\TBSilver\TBLIBS\STRLIB.TRC” ! Use appropriate
path name
...
LINE INPUT #4: line$
CALL ExplodeN(line$, array(),” “)
...
You should also be cautious when printing strings to text files for later input. Remember that
the INPUT statement requires double quotes around strings containing commas or leading