Operator Properties

The Operator Properties dialog has ten somewhat obscure options dealing with operators. "Operator" is used in a very general sense in MathML, and includes things like stretchy arrows and braces.

As with all property dialogs, the Operator Properties dialog is opened from the Properties menu. It is also the default property dialog for operator tokens, and can thus be opened by double-clicking the corresponding MathML elements in the MathML Ancestry panel.

The following properties can be set from this dialog:

Form

This property lets you flag this operator as being an infix, prefix or postfix operator. Changing the form may adjust spacing around the operator slightly. For example, a prefix minus sign has slightly less spacing around it than an infix minus sign.

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Usually the proper form is set automatically by the Editor. The form property may also be used by some MathML software to aid in translation to other formats.

Space to left of operator and Space to right of operator

Setting this property can increase or decrease the default spacing around the operator. You can enter any MathML size value except percentages. If you specify no units, the default is "em", a unit of space used in printing that is roughly the width of a capital 'M'. Enter "automatic" to select MathFlow's default spacing.

Allow stretching, Stretch symmetrically, Min Size, and Max Size

These four options work together to control how operators stretch. Most characters cannot be sensibly stretched, but characters such as parentheses and arrows often "stretch" to match the height or width of some adjacent expression. By setting "allow stretching" to false, you can disable stretching of parentheses, and other characters that are stretchy in MathML by default.

For example, these outer parentheses are stretchy:

Those in this example are not:

If a character is stretchy, then you also have a choice as to whether you want the stretching to be symmetric around the natural axis of the equation. Characters normally stretch symmetrically. However, in situations where a non-symmetric expression is being bracketed by stretchy fences, non-symmetric stretching is needed.

In some situations, you may wish to specify a minimum or maximum amount a stretchy character can grow or shrink, using the min size and max size options. These properties take MathML size values.

Enlarge in display style and Move limits to script positions in inline style

A few characters like integrals and summation signs are typically set in a larger font in a display equation than they are in inline equations where it is good to save space vertically. In MathML, characters can be marked as having a large display form to cause them to set their size depending on how they are used. You can turn off this automatic behavior by setting the property to "false."

Similarly, some large operators, such as summation signs, are traditionally typeset with associated limits in the subscript and superscript positions when the equation appears inline, and they appear above and below the sum in a display equation. You can disable this automatic shift between typesetting styles depending on the context by setting this property to "false."

Treat as an accent for positioning

In normal math typesetting, an underscript or an overscript is displayed in a reduced font size, just as with a normal superscript. However, in many situations, this is not what looks best. In particular, with accent characters like tildes and bars, the size for the accent should match the size of the character over which it is placed. Also, these accent-type characters are usually typeset a bit closer to the character. You can tell MathFlow to treat an overscript as an accent for typesetting purposes by setting this property to "true."