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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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