1 2High quality typesetting of mathematical formulas is a quite tedious 3task. One of the most sophisticated typesetting programs for 4mathematical text \TeX{} \cite{Knuth:84}, together with its widely used 5macro package \LaTeX{} \cite{Lamport:86}, has a strange syntax of 6mathematical formulas, especially of the complicated type. This is the 7main reason which lead us to designing the formula interface between the 8computer algebra system \REDUCE{} and the document preparation system 9\LaTeX{}. The other reason is that all available syntaxes of the 10\REDUCE{} formula output are line oriented and thus not suitable for 11typesetting in mathematical text. The idea of interfacing a computer 12algebra system to a typesetting program has already been used, eg. in 13\cite{Fateman:87} presenting the \TeX{} output of the MACSYMA computer 14algebra system. 15 16The formula interface presented here adds to \REDUCE{} the new syntax of 17formula output, namely \LaTeX{} syntax, and can also be named \REDUCE{} - 18\LaTeX{} translator. Text generated by \REDUCE{} in this syntax can be 19directly used in \LaTeX{} source documents. Various mathematical 20constructions are supported by the interface including subscripts, 21superscripts, font changing, Greek letters, divide-bars, integral and 22sum signs, derivatives etc. 23 24The interface can be used in two ways: 25\begin{itemize} 26\item for typesetting of results of \REDUCE{} algebraic calculations. 27\item for typesetting of users formulas. 28\end{itemize} 29 30The latter can even be used by users unfamiliar with the \REDUCE{} 31system, because the \REDUCE{} input syntax of formulas is almost the 32same as the syntax of the majority of programming languages. We aimed 33at speeding up the process of formula typesetting, because we are 34convinced, that the writing of correct complicated formulas in the 35\REDUCE{} syntax is a much more simpler task than writing them in the 36\LaTeX{} syntax full of keywords and special characters \verb+ \, {, ^+ 37etc. It is clear, that not every formula produced by the interface is 38typeset in the best format from an aesthetic point of view. When a user 39is not satisfied with the result, he can add some \LaTeX{} commands to the 40\REDUCE{} output - \LaTeX{} input. 41 42The interface is connected to \REDUCE{} by three new switches and 43several statements. To activate the \LaTeX{} output mode the switch {\tt 44latex} must be set {\tt on}. this switch, similar to the switch {\tt 45fort} producing FORTRAN output, being {\tt on} causes all outputs to be 46written in the \LaTeX{} syntax of formulas. The switch {\tt VERBATIM} is 47used for input printing control. If it is {\tt on} input to \REDUCE{} system 48is typeset in \LaTeX{} verbatim environment after the line containing 49the string {\tt REDUCE Input:}. 50 51The switch {\tt lasimp} controls the algebraic evaluation of input 52formulas. If it is {\tt on} every formula is evaluated, simplified and 53written in the form given by ordinary \REDUCE{} statements and switches 54such as {\tt factor}, {\tt order}, {\tt rat} etc. In the case when the 55{\tt lasimp} switch is {\tt off} evaluation, simplification or 56reordering of formulas is not performed and \REDUCE{} acts only as a 57formula parser and the form of the formula output is exactly the same as 58that of the input, the only difference remains in the syntax. The mode 59{\tt off lasimp} is designed especially for typesetting of formulas for 60which the user needs preservation of their structure. This switch has 61no meaning if the switch {\tt Latex} is {\tt off} and thus is working 62only for \LaTeX{} output. 63 64For every identifier used in the typeset \REDUCE{} formula 65the following properties can be defined by the statement {\tt defid}: 66\begin{itemize} 67\item its printing symbol (Greek letters can be used). 68\item the font in which the symbol will be typeset. 69\item accent which will be typeset above the symbol. 70\end{itemize} 71 72Symbols with indexes are treated in \REDUCE{} as operators. Each index 73corresponds to an argument of the operator. The meaning of operator 74arguments (where one wants to typeset them) is declared by the statement 75{\tt defindex}. This statement causes the arguments to be typeset as 76subscripts or superscripts (on left or right-hand side of the operator) 77or as arguments of the operator. 78 79The statement {\tt mathstyle} defines the style of formula typesetting. 80The variable {\tt laline!*} defines the length of output lines. 81 82The fractions with horizontal divide bars are typeset by using the 83new \REDUCE{} infix operator \verb+//+. This operator is not 84algebraically simplified. During typesetting of powers the checking on 85the form of the power base and exponent is performed to determine the 86form of the typeset expression (eg. sqrt symbol, using parentheses). 87 88Some special forms can be typeset by using \REDUCE{} prefix operators. 89These are as follows: 90\begin{itemize} 91\item {\tt int} - integral of an expression. 92\item {\tt dint} - definite integral of an expression. 93\item {\tt df} - derivative of an expression. 94\item {\tt pdf} - partial derivative of an expression. 95\item {\tt sum} - sum of expressions. 96\item {\tt product} - product of expressions. 97\item {\tt sqrt} - square root of expression. 98\end{itemize} 99There are still some problems unsolved in the present version of the 100interface as follows: 101\begin{itemize} 102\item breaking the formulas which do not fit on one line. 103\item automatic decision where to use divide bars in fractions. 104\item distinction of two- or more-character identifiers from the product 105 of one-character symbols. 106\item typesetting of matrices. 107\end{itemize} 108 109 110 111\centerline{\bf Remark} 112 113After finishing presented interface, we have found another work 114\cite{Antweiler:89}, which solves the same problem. The RLFI package has 115been described in \cite{Drska:90} too. 116 117 118 119 120\subsection{APPENDIX: Summary and syntax} 121 122{\bf Warning} 123 124The RLFI package can be used only on systems supporting lower case 125letters with {\tt off raise} statement. The package distinquishes the 126upper and lower case letters, so be carefull in typing them. 127In \REDUCE 3.6 the \REDUCE commands have to be typed in lower-case 128while the switch {\tt latex} is {\tt on}, in previous versions 129the commands had to be typed in upper-case. 130 131{\bf Switches} 132 133\begin{description} 134\item[{\tt latex}] 135- If {\tt on} output is in \LaTeX{} format. It turns {\tt off} the {\tt 136raise} switch if it is set {\tt on} and {\tt on} the {\tt raise} switch 137if it is set {\tt off}. By default is {\tt off}. 138\item[{\tt lasimp}] 139- If {\tt on} formulas are evaluated (simplified), \REDUCE{} works 140as usually. If {\tt off} no evaluation is performed and the structure 141of formulas is preserved. By default is {\tt on}. 142\item[{\tt verbatim}] 143- If {\tt on} the \REDUCE{} input, while {\tt latex} switch being {\tt 144on}, is printed in \LaTeX{} verbatim environment. The acutal \REDUCE{} 145input is printed after the line containing the string {\tt "REDUCE 146Input:"}. It turns {\tt on} resp. {\tt off} the {\tt echo} switch when 147turned {\tt on} resp. {\tt off}. by default is {\tt off}. 148\end{description} 149 150{\bf Operators} 151 152\begin{description} 153\item[infix] - \verb+//+ 154\item[prefix] - {\tt int,dint,df,pdf,sum,product,sqrt} and all \REDUCE{} 155prefix operators defined in the \REDUCE{} kernel and the SOLVE module. 156\end{description} 157 158\begin{verbatim} 159 <alg. expression> // <alg. expression> 160 int(<function>,<variable>) 161 dint(<from>,<to>,<function>,<variable>) 162 df(<function>,<variables>) 163 <variables> ::= <o-variable>|<o-variable>,<variables> 164 <o-variable> ::= <variable>|<variable>,<order> 165 <variable> ::= <kernel> 166 <order> ::= <integer> 167 <function> ::= <alg. expression> 168 <from> ::= <alg. expression> 169 <to> ::= <alg. expression> 170 pdf(<function>,<variables>) 171 sum(<from>,<to>,<function>) 172 product(<from>,<to>,<function>) 173 sqrt(<alg. expression>) 174\end{verbatim} 175 176{\tt <alg. expression>} is any algebraic expression. Where appropriate, 177it can include also relational operators (e.g. argument {\tt <from>} of 178{\tt sum} or {\tt product} operators is usually equation). {\tt 179<kernel>} is identifier or prefix operator with arguments as described 180in \cite{Hearn:91}. Interface supports typesetting lists of algebraic 181expressions. 182 183 184{\bf Statements} 185 186\begin{verbatim} 187 mathstyle <m-style>; 188 <m-style> ::= math | displaymath | equation 189 defid <identifier>,<d-equations>; 190 <d-equations> ::= <d-equation> | <d-equation>,<d-equations> 191 <d-equation> ::= <d-print symbol> | <d-font>|<d-accent> 192 <d-print symbol> ::= name = <print symbol> 193 <d-font> ::= font = <font> 194 <d-accent> ::= accent = <accent> 195 <print symbol> ::= <character> | <special symbol> 196 <special symbol> ::= alpha|beta|gamma|delta|epsilon| 197 varepsilon|zeta|eta|theta|vartheta|iota|kappa|lambda| 198 mu|nu|xi|pi|varpi|rho|varrho|sigma|varsigma|tau| 199 upsilon|phi|varphi|chi|psi|omega|Gamma|Delta|Theta| 200 Lambda|Xi|Pi|Sigma|Upsilon|Phi|Psi|Omega|infty|hbar 201 <font> ::= bold|roman 202 <accent> ::=hat|check|breve|acute|grave|tilde|bar|vec| 203 dot|ddot 204\end{verbatim} 205 206For special symbols and accents see \cite{Lamport:86}, p. 43, 45, 51. 207 208\begin{verbatim} 209 defindex <d-operators>; 210 <d-operators> ::= <d-operator> | <d-operator>,<d-operators> 211 <d-operator> ::= <prefix operator>(<descriptions>) 212 <prefix operator> ::= <identifier> 213 <descriptions> ::= <description> | <description>, 214 <descriptions> 215 <description> ::= arg | up | down | leftup | leftdown 216\end{verbatim} 217 218The meaning of the statements is briefly described in the preceding 219text. 220