[self-interest] (Aspects) Utilities in Lisp vs Design Patterns in Smalltalk- Self
dpharris at telus.net
Thu Apr 24 13:49:23 UTC 2003
But, in reality, most people design in both directions at once -- as it
is important to thing about the low-level implementation at the same
time as considering the overall stategy or hight-level shape of the
Jecel Assumpcao Jr wrote:
>On Monday 21 April 2003 13:27, Albertina Lourenci wrote:
>>First of all I would like if someone explain to me
>>if there are differences between bottom-up programming
>>and exploratory programming.
>This is way off topic, but here is a short reply:
>Imagine that a program A is made up of components B, C and D. Suppose
>that component C is made up of subcompenents E and F. This is a tree
>structure, right? As is usual in computer science, imagine the tree
>with the root (A) at the top.
>If you create this program by starting with A and ending with E and F
>you will be doing "top-down design". "bottom-up design" goes in the
>A problem with top-down design is that A can't really run if B, C and D
>haven't been created yet. So the very first time you get to run the
>program is when you have finished writing it! One solution is to create
>small "place holder" components that are dummy versions of B, C and D
>so you can test A and see if it works.
>With a proper interactive environment (such as Self) you can test E as
>soon as you have written it. A more static environment would not allow
>you to call E from a command line and would make you write a program to
>call it (a dummy C, for example).
>Many people plan ahead in a top-down fashion and then program in a
>bottom-up way. Others actually prefer to first think about the low
>level components (leaves of the tree) and play around with them
>exploring what they can do before moving on the the next level.
>A language like Forth forces you to program bottom-up since everything a
>"word" refers to when it is defined must have been previously defined.
>Lisp and Self allow references to things that might not yet exist.
>Aspects are "cross-cutting", as you said yourself, and would represent
>an entirely different direction compared to the up/down axis.
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