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Annotation of 42BSD/usr.lib/learn/eqn/L11.1f, revision 1.1.1.1

1.1       root        1: #once #create message
                      2: .ND
                      3: .tr %$
                      4: .EQ
                      5: delim $$
                      6: .EN
                      7: .LP
                      8: The way to handle the problem of a subscript or superscript
                      9: on nothing is to provide something to hang the subscript
                     10: or superscript on. 
                     11: One possibility is to use a tilde, but that has a real width,
                     12: and might spoil the appearance of the output.
                     13: The best solution is this:
                     14: 
                     15:   "" sup 1 ...
                     16: 
                     17: The expression "" has no width, so everything works
                     18: out properly.  The use of "" may seem a bit unnatural
                     19: but it's an idiom that you get used to quite quickly.
                     20: 
                     21: For practice, modify "Example" so it produces
                     22: output that looks like this,
                     23: then type "ready".
                     24: .pl 1
                     25: #once #create Ref
                     26: .LP
                     27: .EQ
                     28: "" sup + H sub 2 ~ "<=>" ~ "" sup - H ~+~ "" sup + H
                     29: .EN
                     30: .pl 1
                     31: #once #create Example
                     32: .LP
                     33: .EQ
                     34: xxx
                     35: .EN
                     36: .pl 1
                     37: #
                     38: #once neqn Ref | nroff >X1 &
                     39: #once neqn message Ref | nroff -T$term %s/tinyms -
                     40: #user
                     41: neqn Example | nroff >X2
                     42: #cmp X1 X2
                     43: #fail
                     44: Don't forget spaces; don't forget to quote
                     45: things when needed (including <=>).
                     46: #log
                     47: #next
                     48: 11.1g 10

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