Designing with Leo¶
This chapter discusses how outlines can improve the design of programs, web sites and any other complex data. The more complex your program or data, the more useful Leo becomes.
Furthermore, the same features that help with design also help with implementation, maintenance and testing. In all cases, being able to organize, understand and manipulate (script) complex data is what Leo does best.
Contents
Outlines embody design¶
Leo’s outlines don’t merely represent design. They often are the design. Outlines effortlessly show relationships between class, methods or any other data.
Outlines express design and structure directly. In most programs, the grouping of functions into files, or the organization of a single file as a set of functions, etc.
Typical design tools are separate from the resulting product. With Leo, your designs become your programs or web site.
Leo’s outline pane always shows you the big picture, and the relationship of the presently selected outline to that big picture. At all times you are aware of both the overall design and all the intermediate levels of detail.
Outlines create new design dimensions.
There are many ways to express a program as a Leo outline. Such choices are important. They add clarity to the entire program. These are different kind of choices. They simply can not be expressed at all in other editors. In other words, such choices exist in a new design space.
Outlines add a new dimension to the design and coding process. Choices about what sections do, what they are named, what order they appear in, are choices in a design space different from “normal” programming. This an abstract concept, to be sure. However, the previous paragraphs are really a manifestation of working in this new design space.
Nodes hide details¶
Organizer nodes convey information about the structure and design of a large system. Decoupling structure from content in this way is precisely what is needed for flexibility: one can reorganize at will without worrying about changing the meaning of the code.
Outlines clarify the shape of code
These last several paragraphs have discussed comments in detail because the net effect of “putting comments where they belong” is that comments don’t clutter the code. Section references hide irrelevant detail, so larger-scale patterns within functions (or declarations) become more apparent. Often just recasting code into web format has created Aha’s about my own code, with no special attention to recoding or redesign! Recasting a function as a web raises the real and apparent level of abstraction.
Organizer nodes eliminate mundane comments The headline of an organizer node is often all that needs to be said.
Nodes create places for comments
Each of Leo’s nodes provide a place for lengthy comments that do not clutter other code. In practice this encourages comments where they are needed.
Outlines reduce the need for comments
Bridge or transition phrases are almost always unnecessary in a Leo outline. One never needs to say something like, “having just finished with topic x, we turn now to topic y.”
Comments and formatting no longer have to indicate overall design; node do that.
Nodes reduce the visual “weight” of code
Nodes and their helpers (usually in child nodes) can be as complex as necessary without affecting the organization of the outline. Moreover, collapsed nodes are inconspicuous, no matter how many children they contain and no matter how much code each child contains.
Clones create views¶
Typical browsers show you a fixed view of code. In contrast, Leo allows you to organize your programs as you want, and Leo remembers your organizations.
Furthermore, Leo does not constrain you to a single “right” view of your data, programs or designs. By using clones, a single outline may contain dozens or even thousands of views of the nodes in the outline. You are free to create a new view for every new task or project.
Finally, you can insert organizer nodes anywhere in an outline, including anywhere in any view. Organizer nodes do not change the meaning of programs, html pages or web sites, yet they can clarify and simplify designs, programs, web sites or data.
Nodes create context¶
Nodes naturally provide useful context. For example, @button and @test nodes.
Outlines provide a convenient way of expressing the intended scope of commands. Many of Leo’s commands operates on the presently selected tree.
