[Info-vax] Pascal question

[Arne Vajhøj]

On 1/21/2019 10:52 PM, Dave Froble wrote:
> John, did any other languages (besides Basic) use the VMS dynamic string 
> types?
> 
> The implementation on Basic+ was rather interesting.  If one set string 
> A$ = B$, it would not copy the data, it changed the pointer for A$ to 
> the same value as the pointer for B$.  Things could get interesting.  If 
> A$ was a label in an I/O buffer, it would no longer be a label in the 
> buffer.

That type of "smart" ideas are still seen.

String is immutable in Java. At least using normal methods, so in
some Java versions use of non-normal methods can give funky results.

$ type StringFun.java
public class StringFun {
     public static void main(String[] args) throws Exception {
         String s1 = "ABCEF";
         System.out.printf("s1=%s\n", s1);
         String s2 = s1.substring(1, 4);
         System.out.printf("s2=%s\n", s2);
         // start dirty
         // note: only access s1 not s2
         java.lang.reflect.Field value = 
String.class.getDeclaredField("value");
         value.setAccessible(true);
         char[] buf = (char[])value.get(s1);
         buf[2] = 'X';
         // end dirty
         System.out.printf("s1=%s\n", s1);
         System.out.printf("s2=%s\n", s2);
     }
}
$ @sys$startup:java$60_setup
$ java -version
java version "1.6.0"
Java(TM) SE Runtime Environment "1.6.0-7"
Java HotSpot(TM) 64-Bit Server VM (build 20.7-b07, mixed mode)
$ javac StringFun.java
$ java StringFun
s1=ABCEF
s2=BCE
s1=ABXEF
s2=BXE
$ @sys$startup:java$80_setup
$ javac StringFun.java
$ java StringFun
s1=ABCEF
s2=BCE
s1=ABXEF
s2=BCE

:-)

Arne