Scripting the techexplorer Hypermedia Browser

Input mathematics with the expression editor

The expression editor is a Java applet for editing mathematical expressions that exemplifies the use of the techexplorer Java interface to the Document Object Model (DOM) API. With the expression editor you can use the keyboard and mouse to create and edit mathematical structures that have been created either for the purpose of displaying mathematics in a document or performing a scientific computation.

The design of the expression editor is distinguished by three interrelated subcomponents:

1. it is based on a hierarchy of mathematical objects that relates to either or both the graphical rendering of the mathematics on the printed page, and the interpretation of the formulas by a computational system;
2. it provides for WYSIWYG (``what-you-see-is-what-you-get'') editing of mathematics by use of a single visual cue: a highlighted subexpression; and,
3. it correlates these mathematical objects and single visual cue with keyboard actions for purposes of insertion, deletion, and navigation.

In what follows we introduce the basic use of the expression editor by examining how to create a basic expression, use the arrow keys, insert and delete mathematical expressions, undo and redo, and and matrix edit commands. We conclude with recommendations for the use of the expression editor.

Once you are ready start editing equations!

Creating a Basic Expression

First here is how you create an expression from scratch. The expression editor first presents you with an empty box. You fill this box with the first character that you type from the keyboard. As you type in new characters, the highlight moves to the right.

The expression editor has a single visual clue, a highlighted current expression. Here is a summary of basic principles:

• An empty box denotes an expression to be filled in. Your initial expression is an empty box. In general, your expression may containing any number of empty boxes.

• The current expression is highlighted. Each new expression you type becomes the new current expression, i.e. becomes highlighted.

• Variables names have single alphabetic characters. Thus xy is interpreted as the product of two variables x and y.

• LaTeX control words are entered with a backslash. For LaTex control words, type a backslash (\) then one of more leading alphabetic letters of its name. Use TAB to complete the word as far as possible, then any non-alphabetic character to accept that completion. Alternatively, right-click on the characters typed so far to get a context menu of choices for completions.

• An open-parenthesis creates an empty enclosed expression. Typing an open parenthesis, bracket, or brace, creates an empty enclosed expression. Want to change them? Use the right/left-arrow keys to move to the delimiter then type a new one (use a dot "." if you want it invisible).

• A close-parenthesis wraps the highlighted expression in parentheses. Typing a closed parenthesis, bracket, or brace wraps the the current expression with identical delimiters.

• Typing the infix operator + gives you an empty box for the right operand. Operators + - = and / create no two-dimensional structure but always give you an empty box for the right operand.

• Type ALT+s (or infix '_') to create a subscript Typing ALT+s creates an empty box for a subscript. You can then rotate this box in the same direction (clockwise) using ALT+r. Once a script is given, use ALT+a to add an additional script. Other two-dimensional structures are created by ALT+p (or '^') for powers, ALT+d (or '%') for divisions, ALT+q for square roots, and ALT+o for general roots.

Arrow Keys

As is customary with text editors, the arrow keys move you in the direction indicated by the arrow. Left and right arrow move you systematically across the characters of the math expression. Up and down move from superscript to subscript, numerator to denominator, and so on. Adding the CTRL key, lets you navigate the math expression as a tree structure.

• CTRL+Left and CTRL+Right move across siblings. Adding CTRL to the left- and right-arrow keys move the highlight to the left or right sibling of the current expression tree.

• CTRL+Up means larger. Type CTRL+up arrow to move the highlight to the parent of the current expression.

• CTRL+Down means smaller. Type CTRL+down arrow to move the highlight to a child of the current expression.

• CTRL+SHIFT+Right/Left means extend. When the CTRL+SHIFT key is held down when typing the right- or left-arrow, the highlight is extended in the direction of the arrow.

Insertion and Deletion

• New characters are always inserted to the right unless preceeded by an INSERT.. The characters you type are always inserted to the right of the currently highlighted expression. If you must insert a character to the left, just precede the character by an INSERT.

• DELETE and BACKSPACE ( or ALT+b ) delete the current expression.
  • The DELETE key deletes the current expression and moves the highlight to the right.
  • The BACKSPACE key deletes the current expression and moves the highlight to the left.

• DELETE and BACKSPACE delete enclosing parentheses. Once you have an expression enclosed in any kind of left-right delimiters: parentheses, brackets, or curly brackets, typing DELETE or BACKSPACE replaces the enclosed expresssion by the expression itself.

• DELETE and BACKSPACE are used to edit control words and numbers. Numbers are consecutive strings of digits containing an optional decimal point. While creating a number or control word, the right- and left-arrow keys, DELETE, and BACKSPACE may be used to edit their contents. Thereafter numbers and control words becomes nodes of the expression tree. To re-edit either, type a down-arrow.

Undo and Redo

• UNDO ( CTRL+z ) cancels the last action. To undo the last keyboard action, issue an UNDO by typing CTRL+Z. A second UNDO undoes the next-to-last keyboard action. And so on.

• REDO (CTRL+y ) cancels UNDO. To cancel an UNDO, issue a REDO by typing CTRL+Y. The first REDO cancels the effect of the last UNDO. A second REDO cancels the next-to-last UNDO. And so on. A REDO does nothing unless it immediately follows an UNDO or REDO.

• UNDO cancels REDO. An UNDO immediately following a REDO cancels the effect of the REDO.

The example below illustrates the use of DELETE, UNDO, and REDO to edit the last expression produced above.

Matrices

• ALT+m creates a 2-by-2 matrix of empty boxes. The 1-1 element becomes its initial current expression.
  • Matrices appear without a border. Add whatever you like.

• Use ENTER to insert rows and columns
  • Type ENTER to insert an empty row below a highlighted element.
  • Add the CTRL key to insert an empty column to the right of the highlighted element.
  • Add the SHIFT key to insert a row above or a column to the left of the highlighted element.

• Use the arrow keys and TAB to traverse the elements.
  • Use the left/right arrow keys to walk across the characters and elements of the matrix.
  • Add the CTRL key to traverse the elements.
  • Use the up/down arrow keys to move up/down the columns.
  • Type TAB to jump to the next row element.
  • Add the CTRL key to jump to the next column element.
  • Add the SHIFT key to jump to the previous row or column element.

• Use the arrow keys to move to and traverse rows and columns
  • Use CTRL+up arrow to move the highlight from an element to the row containing the element.
  • Use ALT+r ("rotate") to rotate the highlight from a row to a column or vice-versa.
  • Use CTRL+left/right arrows to move highlight along the rows or columns.
  • Use another CTRL+up arrow to move the highlight from a row or column to the entire matrix.
  • Use CTRL+down to move the highlight from a matrix to a row/column, or a row/column to a element.

• DELETE or BACKSPACE work as usual
  • Both replace a highlighted element by an empty box, moving the highlight right or left.
  • Both delete a highlighted row, moving the highlight down or up.
  • Both delete a highlighted column, moving the highlight right or left.
  • Both delete a highlighted matrix, moving the highlight right or left.

Recomended techexplorer settings

• Colors recommendation: suggest light gray--bottom row, 3rd from right, in table of basic colors for Selection Background( Options...->Colors from context menu on the Expression Editor window)
• Font recommendation: Times New Roman 13 for normal and italic math (Options...-->Fonts from context menu on Expression Editor window).

IBM techexplorer Hypermedia Browser is a trademark of the IBM Corporation. Send comments and questions to techexpl@us.ibm.com.