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Annotation of 43BSDReno/share/doc/usd/27.eqnguide/g3, revision 1.1

1.1     ! root        1: .\"    @(#)g3  6.1 (Berkeley) 5/22/86
        !             2: .\"
        !             3: .SC "Shorthand for In-line Equations"
        !             4: .PP
        !             5: In a mathematical document,
        !             6: it is necessary to follow mathematical conventions
        !             7: not just in display equations,
        !             8: but also in the body of the text,
        !             9: for example by making variable names like $x$ italic.
        !            10: Although this could be done by surrounding the appropriate parts
        !            11: with
        !            12: .UC .EQ
        !            13: and
        !            14: .UC .EN ,
        !            15: the continual repetition of
        !            16: .UC .EQ
        !            17: and
        !            18: .UC .EN
        !            19: is a nuisance.
        !            20: Furthermore, with `\(mims',
        !            21: .UC .EQ
        !            22: and
        !            23: .UC .EN
        !            24: imply a displayed equation.
        !            25: .PP
        !            26: .UC EQN
        !            27: provides a shorthand for short in-line expressions.
        !            28: You can define two characters to mark the left and right ends
        !            29: of an in-line equation, and then type expressions right in the middle of text
        !            30: lines.
        !            31: To set both the left and right characters to dollar signs, for example,
        !            32: add to the beginning of your document the three lines
        !            33: .P1
        !            34:  .EQ
        !            35:  delim %%
        !            36:  .EN
        !            37: .P2
        !            38: Having done this, you can then say things like
        !            39: .P1
        !            40: .fi
        !            41: Let %alpha sub i% be the primary variable,
        !            42: and let %beta% be zero.
        !            43: Then we can show that %x sub 1% is %>=0%.
        !            44: .P2
        !            45: This works as
        !            46: you might expect _
        !            47: spaces, newlines, and so on are significant
        !            48: in the text, but not in the equation part itself.
        !            49: Multiple equations can occur in a single input line.
        !            50: .PP
        !            51: Enough room is left before and after a line that contains
        !            52: in-line expressions
        !            53: that something like
        !            54: $sum from i=1 to n x sub i$
        !            55: does not interfere with the lines surrounding it.
        !            56: .PP
        !            57: To turn off the delimiters,
        !            58: .P1
        !            59:  .EQ
        !            60:  delim off
        !            61:  .EN
        !            62: .P2
        !            63: Warning: don't use braces, tildes, circumflexes, or double quotes as delimiters _
        !            64: chaos will result.
        !            65: .SC "Definitions"
        !            66: .PP
        !            67: .UC EQN
        !            68: provides a facility so you can give
        !            69: a frequently-used string of characters a name,
        !            70: and thereafter just type the name instead of the
        !            71: whole string.
        !            72: For example, if the sequence
        !            73: .P1
        !            74: x sub i sub 1 + y sub i sub 1
        !            75: .P2
        !            76: appears repeatedly throughout a paper,
        !            77: you can save re-typing it each time by defining it like this:
        !            78: .P1 2
        !            79: define  xy  'x sub i sub 1 + y sub i sub 1'
        !            80: .P2
        !            81: This makes
        !            82: .ul
        !            83: xy
        !            84: a shorthand for whatever characters occur between the single quotes
        !            85: in the definition.
        !            86: You can use any character instead of quote to mark the ends of the definition,
        !            87: so long as it doesn't appear inside the definition.
        !            88: .PP
        !            89: Now you can use
        !            90: .ul
        !            91: xy
        !            92: like this:
        !            93: .P1
        !            94: ^EQ
        !            95: f(x) = xy ...
        !            96: ^EN
        !            97: .P2
        !            98: and so on.
        !            99: Each occurrence of
        !           100: .ul
        !           101: xy
        !           102: will expand into what it was defined as.
        !           103: Be careful to leave spaces or their equivalent
        !           104: around the name
        !           105: when you actually use it, so
        !           106: .UC EQN
        !           107: will be able to identify it as special.
        !           108: .PP
        !           109: There are several things to watch out for.
        !           110: First, although definitions can use previous definitions,
        !           111: as in
        !           112: .P1
        !           113:  .EQ
        !           114:  define  xi  ' x sub i '
        !           115:  define  xi1  ' xi sub 1 '
        !           116:  .EN
        !           117: .P2
        !           118: .ul
        !           119: don't define something in terms of itself'
        !           120: A favorite error is to say
        !           121: .P1
        !           122: define  X  ' roman X '
        !           123: .P2
        !           124: This is a guaranteed disaster,
        !           125: since X
        !           126: .ul
        !           127: is
        !           128: now defined in terms of itself.
        !           129: If you say
        !           130: .P1
        !           131: define  X  ' roman "X" '
        !           132: .P2
        !           133: however, the quotes
        !           134: protect the second X,
        !           135: and everything works fine.
        !           136: .PP
        !           137: .UC EQN
        !           138: keywords can be redefined.
        !           139: You can make
        !           140: / mean
        !           141: .ul
        !           142: over
        !           143: by saying
        !           144: .P1
        !           145: define  /  ' over '
        !           146: .P2
        !           147: or redefine
        !           148: .ul
        !           149: over
        !           150: as /
        !           151: with
        !           152: .P1
        !           153: define  over  ' / '
        !           154: .P2
        !           155: .PP
        !           156: If you need different things
        !           157: to print on a terminal and on the typesetter, it is sometimes worth
        !           158: defining a symbol differently in
        !           159: .UC NEQN
        !           160: and
        !           161: .UC EQN .
        !           162: This can be done with
        !           163: .ul
        !           164: ndefine
        !           165: and
        !           166: .ul
        !           167: tdefine.
        !           168: A definition made with
        !           169: .ul
        !           170: ndefine
        !           171: only takes effect if you are running
        !           172: .UC NEQN ;
        !           173: if you use
        !           174: .ul
        !           175: tdefine,
        !           176: the definition only applies for
        !           177: .UC EQN .
        !           178: Names defined with plain
        !           179: .ul
        !           180: define
        !           181: apply to both
        !           182: .UC EQN 
        !           183: and
        !           184: .UC NEQN .
        !           185: .SC "Local Motions"
        !           186: .PP
        !           187: Although
        !           188: .UC EQN
        !           189: tries to get most things at the right place on the paper,
        !           190: it isn't perfect, and occasionally you will need to tune
        !           191: the output to make it just right.
        !           192: Small extra horizontal spaces can be obtained with
        !           193: tilde and circumflex.
        !           194: You can also say
        !           195: .ul
        !           196: back n
        !           197: and
        !           198: .ul
        !           199: fwd n
        !           200: to move small amounts horizontally.
        !           201: .ul
        !           202: n
        !           203: is how far to move in 1/100's of an em (an em is about the width
        !           204: of the letter
        !           205: `m'.)
        !           206: Thus
        !           207: .ul
        !           208: back 50
        !           209: moves back about half the width of an m.
        !           210: Similarly you can move things up or down with
        !           211: .ul
        !           212: up n
        !           213: and
        !           214: .ul
        !           215: down n.
        !           216: As with 
        !           217: .ul
        !           218: sub
        !           219: or
        !           220: .ul
        !           221: sup,
        !           222: the local motions affect the next thing in the input,
        !           223: and this can be something arbitrarily complicated if it is enclosed
        !           224: in braces.

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