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5 Symbols
curves can also place symbols. \curvesymbol must first define the symbol as anything a \put or \multiput may draw. A negative symbol count between drawing command and coordinates e.g., \tagcurve[-3](0,100,...) fixes the number of symbols per curve segment.
These commands draw flight times and successive positions in the following drawing:
__
\newcounter{time}
___\curvesymbol{\thetime\,s\addtocounter{time}{1}}
___\put(5,4){\curve[-2](0,0, 9.8,19.6, 19.6,0)}
___\curvesymbol{\phantom{\circle*{1}}\circle*{1}}
___\put(5,2){\curve[-2](0,0, 9.8,19.6, 19.6,0)}
_
where \phantom is a plain TEX command from the TEXbook.

Successive positions of a sphere with initial position m,
initial velocity m/s, and acceleration m/s.
The flight time is recorded above each sphere position.
Fixed spacing of symbols at lengths other than the segment's requires more commands. Empty
\curvedashes, empty \curvesymbol and negative symbol count stops drawing so a drawing command will calculate \curvelength only. \curvesymbol then resets the symbol and \curvedashes sets the spacing to its pattern length. If there are no symbols at the ends, \overhang pulls symbols along the curve. The last command with no symbol count draws the symbols.
\arc and \bigcircle use sixteen segments for a circle so if eight symbols are required the fixed spacing technique is necessary. The following commands draw the pin numbers on a relay base:
____
\newcounter{pin}
___\curvedashes{}
___\curvesymbol{}
___\put(60,60){\arc[-1](40,0){-360}}
___\setlength{\curvelength}{0.125\curvelength}
___\curvedashes[\curvelength]{1}
___\setlength{\overhang}{0.5\curvelength}
___\curvesymbol{\addtocounter{pin}{1}\thepin}
___\put(60,60){\arc(40,0){-360}}
_

The pin numbering of plug-in relays is clockwise
from the spigot key when viewed from below.
If symbols and dash pattern exist and \overhang is 0pt, curves draw the first position blank. For equal spacing they draw the last position blank if rounding error causes the last pattern to be slightly short. If \renewcommand changes \diskpitchstretch, rounding error changes and the final symbol may reappear. To avoid fiddling with \diskpitchstretch for closed curves with symbols equally spaced, use an \overhang which is a fraction of a pattern length as in the previous example.