In programming the "fluent" style programming has been adopted quite widely (cf.
<https://en.wikipedia.org/wiki/Fluent_interface>). It allows one to nicely code
multiple
assignments/method invocations on the same object, by making sure that each
such invocation returns
itself (the object in which the method gets activated) as a result, such that
the next invocation is
working with the same object. This allows one to cascade method invocations. In
ooRexx the double
tilde/twiddle "~~" allows one to employ this "fluent" style of programming as
ooRexx will carry out
the appropriate mechanics.
Using the fluent programming style induces programming sequences like (C++
example from the above URL):
FluentGlutApp(argc,
argv).withDoubleBuffer().withRGBA().withAlpha().withDepth().at(200,
200).across(500, 500).named("My OpenGL/GLUT App").create();
or (the same C++ program, better legible, i.e. easier to read/understand and
less error-prone):
FluentGlutApp(argc, argv) .withDoubleBuffer() .withRGBA() .withAlpha()
.withDepth() .at(200,
200).across(500, 500) .named("My OpenGL/GLUT App") .create();
It would be possible in ooRexx to define a class "FluentGlutApp" and invoke all
the methods by using
the double twiddle message operator of ooRexx, yielding, e.g. an ooRexx program
matching the above
C++ program:
FluentGlutApp(argc,
argv)~new~~withDoubleBuffer~~withRGBA~~withAlpha~~withDepth~~at(200,
200)~~across(500, 500)~~named("My OpenGL/GLUT App")~~create
This is actually quite a powerful built-in feature of the ooRexx language.
However, in order to make
the ooRexx programm better legible, one needs to break it up like:
FluentGlutApp(argc, argv)~new - ~~withDoubleBuffer- ~~withRGBA-
~~withAlpha- ~~withDepth-
~~at(200, 200)- ~~across(500, 500) - ~~named("My OpenGL/GLUT App")- ~~create
The code is better legible, however we have to add another operator to the end
(a hyphen or a
comma). It would be easier to read, if it was possible to code in ooRexx:
FluentGlutApp(argc, argv)~new
~~withDoubleBuffer~~withRGBA~~withAlpha~~withDepth~~at(200,
200)~~across(500, 500) ~~named("My OpenGL/GLUT App")~~create
Of course, in ooRexx it should be possible to intermix single message operators
(~) and double
message operators (~) in such multiline message statements.
The rule would be for the parser that if the next line begins with a single or
double message
operator, that it is regarded to be a split statement. If there are resulting
errors, the normal
ooRexx error messages can be employed therafter.
---rony
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