Some notes on VisualWorks Smalltalk:

1) Interactive testing and debugging output can be conveniently displayed
in the system transcript display of the VW Launcher window by sending
appropriate messages to global variable Transcript.  The standard way
to do this is illustrated by

   Transcript show: aString; cr

which causes the String aString to be displayed in the transcript, followed
by a carriage return.


2) printOn: is used by the print: method for Transcript,  but the results
are not quite what would be expected.  If X is an instance of a class for
which printOn: has been provided, then the value of X as defined by the
printOn: method can be displayed on Transcript by

  Transcript print: X; endEntry.

but as indicated above, the format is not quite what is normally desired.


3) The method printString is predefined for many predefined nonString
classes.  It returns a string representation of its receiver that is
appropriate for printing.  (Note that the reason for the name "printString"
is that it returns a string for printing, not that it prints a string.)
Thus, for example,

   Transcript show: (17 printString); cr.

causes "17" (without quotes) to be printed on the transcript.  To be
consistent with the predefined methods, it is often a good idea to
define a printString method for user-defined classes.


4) The withCRs method for instances of String returns the string obtained
by replacing each of the backslash characters (\) of the target string
(receiver of the withCRs message) by a carriage-return character.  For
example, if s is a string, then the value of

   s withCRs

is the value of s with all '\' characters replaced by a CR character.
In building a string for a printString method, it is convenient to
initially use backslash characters where a CR is desired, and then use
withCRs to convert all the backslash characters to CRs as the last step.



Some differences between VW Smalltalk and GNU Smalltalk:

(Each of the following applies to VW Smalltalk.)

1) The nl method in GNU Smalltalk is cr in VisualWorks.

2) A string parameter (not nil) is required for the category: component
of a class definition.

3) Global variable names must begin with an upper-case letter.

4) There is no printNl.

5) !! is considered to be a single symbol. (Use ! ! instead.)