1.10.3 Editing and Evaluating Two-Dimensional Expressions
When you see a two-dimensional expression on the screen, you can edit it much as you would edit text. You can for example place your cursor somewhere and start typing. Or you can select a part of the expression, then remove it using the Delete key, or insert a new version by typing it in.
In addition to ordinary text editing features, there are some keys that you can use to move around in two-dimensional expressions.
Ways to move around in two-dimensional expressions.
This shows the sequence of subexpressions selected by repeatedly typing ..
Ways to evaluate two-dimensional expressions.
In most computations, you will want to go from one step to the next by taking the whole expression that you have generated, and then evaluating it. But if for example you are trying to manipulate a single formula to put it into a particular form, you may instead find it more convenient to perform a sequence of operations separately on different parts of the expression.
You do this by selecting each part you want to operate on, then inserting the operation you want to perform, then using Shift-Control-Enter or Command-Return.
Here is an expression with one part selected.
Pressing Shift-Control-Enter evaluates the selected part.