|  | NAME     
 |  |  |  | eqn – typeset mathematics 
 | 
 SYNOPSIS     
 |  |  |  | eqn [ option ... ] [ file ... ] 
 | 
 DESCRIPTION     
 |  |  |  | Eqn is a troff(1) preprocessor for typesetting mathematics on
    a typesetter. Usage is almost always If no files are specified, eqn reads from the standard input.
    Eqn prepares output for the typesetter named in the −Tdest option
    (default −Tutf; see troff(1)). When run with other preprocessor
    filters, eqn usually comes last. 
    
    
    A line beginning with .EQ marks the start of an equation; the
    end of an equation is marked by a line beginning with .EN. Neither
    of these lines is altered, so they may be defined in macro packages
    to get centering, numbering, etc. It is also possible to set two
    characters as ‘delimiters’; text between delimiters is also eqn
    input. Delimiters may be set to
    characters x and y with the option −dxy or (more commonly) with
    delim xy between .EQ and .EN. Left and right delimiters may be
    identical. (They are customarily taken to be $font L "$$" )$. Delimiters
    are turned off by delim off. All text that is neither between
    delimiters nor between .EQ and .EN is passed through untouched.
    
    
    
    Tokens within eqn are separated by spaces, tabs, newlines, braces,
    double quotes, tildes or circumflexes. Braces {} are used for
    grouping; generally speaking, anywhere a single character like
    x could appear, a complicated construction enclosed in braces
    may be used instead. Tilde ~ represents a full space in the output,
    circumflex ^ half as much. 
    
    
    Subscripts and superscripts are produced with the keywords sub
    and sup. Thus x sub i makes $x sub i$, a sub i sup 2 produces
    $a sub i sup 2$, and e sup {x sup 2 + y sup 2} gives $e sup {x
    sup 2 + y sup 2}$. 
    
    
    Over makes fractions: a over b yields $a over b$. 
    
    
    Sqrt produces square roots: 1 over sqrt {ax sup 2 +bx+c} results
    in $1 over sqrt {ax sup 2 +bx+c}$ . 
    
    
    The keywords from and to introduce lower and upper limits on arbitrary
    things: $lim from {n -> inf} sum from 0 to n x sub i$ is made with
    lim from {n −> inf} sum from 0 to n x sub i. 
    
    
    Left and right brackets, braces, etc., of the right height are
    made with left and right: left [ x sup 2 + y sup 2 over alpha
    right ] ~=~1 produces $left [ x sup 2 + y sup 2 over alpha right
    ] ~=~1$. The right clause is optional. Legal characters after
    left and right are braces, brackets, bars, c and f for ceiling
    and floor, and "" for
    nothing at all (useful for a right-side-only bracket). 
    
    
    Vertical piles of things are made with pile, lpile, cpile, and
    rpile: pile {a above b above c} produces $pile {a above b above
    c}$. There can be an arbitrary number of elements in a pile. lpile
    left-justifies, pile and cpile center, with different vertical
    spacing, and rpile right justifies. 
    
    
    Matrices are made with matrix: matrix { lcol { x sub i above y
    sub 2 } ccol { 1 above 2 } } produces $matrix { lcol { x sub i
    above y sub 2 } ccol { 1 above 2 } }$. In addition, there is rcol
    for a right-justified column. 
    
    
    Diacritical marks are made with prime, dot, dotdot, hat, tilde,
    bar, under, vec, dyad, and under: x sub 0 sup prime = f(t) bar
    + g(t) under is $x sub 0 sup prime = f(t) bar + g(t) under$, and
    x vec = y dyad is $x vec = y dyad$. 
    
    
    Sizes and fonts can be changed with prefix operators size n, size
    ±n, fat, roman, italic, bold, or font n. Size and fonts can be
    changed globally in a document by gsize n and gfont n, or by the
    command-line arguments −sn and −fn. 
    
    
    Normally subscripts and superscripts are reduced by 3 point sizes
    from the previous size; this may be changed by the command-line
    argument −pn. 
    
    
    Successive display arguments can be lined up. Place mark before
    the desired lineup point in the first equation; place lineup at
    the place that is to line up vertically in subsequent equations.
    
    
    
    Shorthands may be defined or existing keywords redefined with
    define: define thing % replacement % defines a new token called
    thing which will be replaced by replacement whenever it appears
    thereafter. The % may be any character that does not occur in
    replacement. 
    
    
    Keywords like sum ( sum ), int ( int ), inf ( inf ), and shorthands
    like >= (>=), −> (->), and != ( != ) are recognized. Greek letters
    are spelled out in the desired case, as in alpha or GAMMA. Mathematical
    words like sin, cos, log are made Roman automatically. Troff(1)
    four-character escapes like \(lh (<=) can be used anywhere. Strings
    enclosed in
    double quotes " " are passed through untouched; this permits keywords
    to be entered as text, and can be used to communicate with troff
    when all else fails.
 
 | 
 FILES     
 |  |  |  | /sys/lib/troff/font/devutf   font descriptions for PostScript 
 | 
 SOURCE     
 SEE ALSO     
 |  |  |  | troff(1), tbl(1) J. F. Ossanna and B. W. Kernighan, “Troff User’s Manual”.
 B. W. Kernighan and L. L. Cherry, “Typesetting Mathematics--User’s
    Guide”, Unix Research System Programmer’s Manual, Tenth Edition,
    Volume 2.
 
 | 
 BUGS     
 |  |  |  | To embolden digits, parens, etc., it is necessary to quote them,
    as in bold "12.3". delim off 
 | 
 |  |