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B.7  Mathematical Formulas

B.7.1  Math Mode Environment

The three ways to use math mode ($...$, \(...\) and \begin{math}...\end{math}) are supported. The three ways to use display math mode ($$...$$, \[...\] and \begin{displaymath}... \end{displaymath}) are also supported. Furthermore, \ensuremath behaves as expected.

The equation, eqnarray, eqnarray* environments are supported. Equation labeling and numbering is performed in the first two environments, using the equation counter. Additionally, numbering can be suppressed in one row of an eqnarray, using the \nonumber command.

Math mode is not as powerful in HEVEA as in LATEX. The limitations of math mode can often be surpassed by using math display mode. As a matter of fact, math mode is for in-text formulas. From the HTML point of view, this means that math mode does not close the current flow of text and that formulas in math mode must be rendered using text-level elements only. By contrast, displayed formulas can be rendered using block-level elements. This means that HEVEA have much more possibilities in display context than inside normal flow of text. In particular, stacking text elements one above the over is possible only in display context. For instance compare how HEVEA renders $\frac{1}{\sum_{i=1}^{\infty}$ as: 1/ Si=1¥ ii, and $$\frac{1}{\sum_{i=1}^{\infty}$$ as:
1

¥
S
i=1
ii

B.7.2  Common Structures

HEVEA admits, subscript (_), superscripts (^) and fractions (\frac{numer}{denom}). The best effect is obtained in display mode, where HTML <TABLE> element is extensively used. However, in-text simple subscript and superscript are rendered using the <SUB> and <SUP> text-level elements and their appearance should be correct both in in-text and displayed formulas.

The nth root command \sqrt is not supported.

An attempt is made to render all ellipsis constructs (\ldots, \cdots, \vdots and \ddots). The effect may be strange for the latter two.

B.7.3  Mathematical symbols

Symbols that can be printed using browser iso-latin1 or symbol fonts are translated. Other symbols are undefined most of the time. Attempting to translate them will thus generate ``Unknown macro'' warnings. Then, users can choose their own replacement for these symbols. These personal definitions are best placed in an ad-hoc style file, given as a command line argument to HEVEA. A suggested replacement is a mix of colors and available symbols. For instance, HEVEA cannot render the \leadsto symbol, but it can be defined as a red arrow by:
\newcommand{\leadsto}{{\red\rightarrow}}
Then, $$A \leadsto B$$ is rendered as follows:
A ® B

When given the -nosymb option, HEVEA silently replaces symbols that cannot be rendered by iso-latin1 only by text equivalents. These equivalents are English words by default, or French words when the -francais option is set.

Log-like functions and variable sized-symbols are recognized and their subscripts and superscripts are put where they should in display mode. Subscript and superscript placement can be changed using the \limits and \nolimits commands. Big delimiters are also handled.

B.7.4  Putting one thing above the other

The commands \stackrel, \underline and \overline are recognized. They produce sensible output in display mode. In text mode, these macros call the \textstackrel, \textunderline and \textoverline macros. These macros perform the following default actions, which can be changed by redefining them:
\textstackrel
Performs ordinary superscripting.
\textunderline
Underlines its argument, using the HTML <U> text-level element.
\textoverline
Sends a warning message to the console and echoes its argument in the output.
Math accents (\hat, \tilde, etc.) are not handled at all.

B.7.5  Spacing

By contrast with LATEX, space in the input matters in math mode. One or more spaces are translated to one space. Furthermore, spaces after commands (such as \alpha) are echoed except for invisible commands (such as \tt). This allows users to control space in their formulas, output being near to what can be expected.

Explicit spacing commands (\,, \!, \: and \;) are recognized, the first two commands do nothing, while the others two output one space.

B.7.6  Changing Style

Letters are always italicized inside math mode and this cannot be changed. The appearance of other symbols can be changed using LATEX2e style changing commands (\mathrm, etc.). The commands \boldmath and \unboldmath are not recognized. Whether symbols belonging to the symbol font are affected by these changes or not is browser dependent.

Observe that this does not corresponds directly to how LATEX manage style in math mode.

Math style changing declarations \displaysyle and \textstyle do not exist, while \scriptstyle and \scriptscriptstyle perform type size changes.


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