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############################################################################
#
# File: xgtrace.icn
#
# Subject: Procedures to draw traces of points
#
# Author: Ralph E. Griswold
#
# Date: November 19, 1997
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# As used here, the term "trace" refers to a sequence of points that
# generally consists of locations on a curve or other geometrical object.
#
############################################################################
#
# Requires: Version 9 graphics
#
############################################################################
#
# Links: gtace, turtle
#
############################################################################
link gtrace
link turtle
#
# line_trace(call) draws lines along the figure described by the trace from
# invoke(call).
procedure line_trace(call)
local TPlot, point
TPlot := TGoto # go to first point
every point := invoke(call) do {
TPlot(point.x, point.y)
TPlot := TDrawto # draw subsequently
}
return
end
#
# segment_trace(call) draws line segments between successive pairs of
# points along the figure described by the trace from invoke(call).
procedure segment_trace(call)
local TPlot, TPlotNext, point
TPlot := TGoto # go to first point
TPlotNext := TDrawto
every point := invoke(call) do {
TPlot(point.x, point.y)
TPlot :=: TPlotNext # draw subsequently
}
return
end
#
# curve_trace(call) draws a curve along the figure described by the trace
# from invoke(call).
#
procedure curve_trace(call, limit)
local points, n
/limit := 500 # maximum number of points allowed
DrawCurve ! coord_list(call, limit)
return
end
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