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Determine if two triangles overlap: Difference between revisions

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Determine if two triangles overlap (view source)

Revision as of 20:58, 12 January 2022

29,732 bytes added ,  2 years ago
m
→‎{{header|Phix}}: added syntax colouring, marked p2js compatible
(→‎{{header|Haskell}}: added Haskell solution)
m (→‎{{header|Phix}}: added syntax colouring, marked p2js compatible)
Line 4,361:
{{trans|zkl}}
Plus draw all eight pairs of triangles for visual confirmation.
<!--<lang Phix>include pGUI.e(phixonline)-->
<span style="color: #000080;font-style:italic;">--
 
-- demo\rosetta\Determine_if_two_triangles_overlap.exw
Ihandle dlg, canvas
--</span>
cdCanvas cddbuffer, cdcanvas
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
 
<span style="color: #008080;">include</span> <span style="color: #000000;">pGUI</span><span style="color: #0000FF;">.</span><span style="color: #000000;">e</span>
constant triangles = {{{{0,0},{5,0},{0,5}},{{0,0},{5,0},{0,6}}},
{{{0,0},{0,5},{5,0}},{{0,0},{0,5},{5,0}}},
{{{0,0},{5,0},{0,5}},{{-10,0},{-5,0},{-1,6}}},
{{{0,0},{5,0},{2.5,5}},{{0,4},{2.5,-1},{5,4}}},
{{{0,0},{1,1},{0,2}},{{2,1},{3,0},{3,2}}},
{{{0,0},{1,1},{0,2}},{{2,1},{3,-2},{3,4}}},
{{{0,0},{1,0},{0,1}},{{1,0},{2,0},{1,1}}},
{{{0,0},{1,0},{0,1}},{{1,0},{2,0},{1,1}}}}
 
procedure draw_triangle(sequence t, integer cx,cy, c)
cdCanvasSetForeground(cddbuffer, c)
cdCanvasBegin(cddbuffer,CD_CLOSED_LINES)
for c=1 to 3 do
atom {x,y} = t[c]
cdCanvasVertex(cddbuffer, cx+x*10, cy+y*10)
end for
cdCanvasEnd(cddbuffer)
end procedure
 
function det2D(sequence triangle)
atom {{p1x,p1y},{p2x,p2y},{p3x,p3y}} := triangle
return p1x*(p2y-p3y) + p2x*(p3y-p1y) + p3x*(p1y-p2y)
end function
 
bool bReversed
function checkWinding(sequence triangle, bool allowReversed)
atom detTri := det2D(triangle);
if detTri<0.0 then
if allowReversed then
bReversed = true
triangle = extract(triangle,{1,3,2})
else
throw("triangle has wrong winding direction")
end if
end if
return triangle
end function
 
function overlap(sequence t1, t2, atom epsilon=0.0, bool allowReversed=false, onBoundary=true)
-- Trangles must be expressed anti-clockwise
bReversed = false
t1 = checkWinding(t1, allowReversed)
t2 = checkWinding(t2, allowReversed)
<span style="color: #004080;">Ihandle</span> <span style="color: #000000;">dlg</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">canvas</span>
for t=1 to 2 do -- check t1 then t2
<span style="color: #004080;">cdCanvas</span> <span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">cdcanvas</span>
for edge=1 to 3 do -- check each edge
sequence p1 = t1[edge],
<span style="color: #008080;">constant</span> <span style="color: #000000;">triangles</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">5</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">6</span><span style="color: #0000FF;">}}},</span>
p2 = t1[mod(edge,3)+1]
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">5</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">5</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">}}},</span>
-- Check all points of trangle 2 lay on the external side
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">5</span><span style="color: #0000FF;">}},{{-</span><span style="color: #000000;">10</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{-</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">6</span><span style="color: #0000FF;">}}},</span>
-- of the edge E. If they do, the triangles do not collide.
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">2.5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">5</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">4</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">2.5</span><span style="color: #0000FF;">,-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">5</span><span style="color: #0000FF;">,</span><span style="color: #000000;">4</span><span style="color: #0000FF;">}}},</span>
integer onside = 0
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">}}},</span>
for k=1 to 3 do
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">4</span><span style="color: #0000FF;">}}},</span>
integer c = compare(det2D({p1,p2,t2[k]}),epsilon)
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">}}},</span>
if onBoundary then
<span style="color: #0000FF;">{{{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">}},{{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">}}}}</span>
if not (c<0) then exit end if
else
<span style="color: #008080;">procedure</span> <span style="color: #000000;">draw_triangle</span><span style="color: #0000FF;">(</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">integer</span> <span style="color: #000000;">cx</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cy</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">c</span><span style="color: #0000FF;">)</span>
if not (c<=0) then exit end if
<span style="color: #7060A8;">cdCanvasSetForeground</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">c</span><span style="color: #0000FF;">)</span>
end if
<span style="color: #7060A8;">cdCanvasBegin</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span><span style="color: #004600;">CD_CLOSED_LINES</span><span style="color: #0000FF;">)</span>
-- -- (the following incomprehensible one-liner is equivalent:)
<span style="color: #008080;">for</span> <span style="color: #000000;">c</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">3</span> <span style="color: #008080;">do</span>
-- if compare(det2D({p1,p2,t2[k]}),epsilon)>-onBoundary then exit end if
<span style="color: #004080;">atom</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">x</span><span style="color: #0000FF;">,</span><span style="color: #000000;">y</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">[</span><span style="color: #000000;">c</span><span style="color: #0000FF;">]</span>
onside += 1
<span style="color: #7060A8;">cdCanvasVertex</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">cx</span><span style="color: #0000FF;">+</span><span style="color: #000000;">x</span><span style="color: #0000FF;">*</span><span style="color: #000000;">10</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">cy</span><span style="color: #0000FF;">+</span><span style="color: #000000;">y</span><span style="color: #0000FF;">*</span><span style="color: #000000;">10</span><span style="color: #0000FF;">)</span>
end for
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
if onside=3 then
<span style="color: #7060A8;">cdCanvasEnd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">)</span>
return iff(onBoundary?"no overlap":"no overlap (no boundary)")
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
end if
end for
<span style="color: #008080;">function</span> <span style="color: #000000;">det2D</span><span style="color: #0000FF;">(</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">triangle</span><span style="color: #0000FF;">)</span>
{t2,t1} = {t1,t2} -- flip and re-test
<span style="color: #004080;">atom</span> <span style="color: #0000FF;">{{</span><span style="color: #000000;">p1x</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p1y</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">p2x</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p2y</span><span style="color: #0000FF;">},{</span><span style="color: #000000;">p3x</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p3y</span><span style="color: #0000FF;">}}</span> <span style="color: #0000FF;">:=</span> <span style="color: #000000;">triangle</span>
end for
<span style="color: #008080;">return</span> <span style="color: #000000;">p1x</span><span style="color: #0000FF;">*(</span><span style="color: #000000;">p2y</span><span style="color: #0000FF;">-</span><span style="color: #000000;">p3y</span><span style="color: #0000FF;">)</span> <span style="color: #0000FF;">+</span> <span style="color: #000000;">p2x</span><span style="color: #0000FF;">*(</span><span style="color: #000000;">p3y</span><span style="color: #0000FF;">-</span><span style="color: #000000;">p1y</span><span style="color: #0000FF;">)</span> <span style="color: #0000FF;">+</span> <span style="color: #000000;">p3x</span><span style="color: #0000FF;">*(</span><span style="color: #000000;">p1y</span><span style="color: #0000FF;">-</span><span style="color: #000000;">p2y</span><span style="color: #0000FF;">)</span>
return iff(bReversed?"overlap (reversed)":"overlap")
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
end function
 
<span style="color: #004080;">bool</span> <span style="color: #000000;">bReversed</span>
function redraw_cb(Ihandle /*ih*/, integer /*posx*/, integer /*posy*/)
<span style="color: #008080;">function</span> <span style="color: #000000;">checkWinding</span><span style="color: #0000FF;">(</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">triangle</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">bool</span> <span style="color: #000000;">allowReversed</span><span style="color: #0000FF;">)</span>
cdCanvasActivate(cddbuffer)
<span style="color: #004080;">atom</span> <span style="color: #000000;">detTri</span> <span style="color: #0000FF;">:=</span> <span style="color: #000000;">det2D</span><span style="color: #0000FF;">(</span><span style="color: #000000;">triangle</span><span style="color: #0000FF;">);</span>
integer cy = 200, cx = 100
<span style="color: #008080;">if</span> <span style="color: #000000;">detTri</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0.0</span> <span style="color: #008080;">then</span>
for i=1 to length(triangles) do
<span style="color: #008080;">if</span> <span style="color: #000000;">allowReversed</span> <span style="color: #008080;">then</span>
sequence {t1,t2} = triangles[i]
<span style="color: #000000;">bReversed</span> <span style="color: #0000FF;">=</span> <span style="color: #004600;">true</span>
draw_triangle(t1,cx,cy,CD_RED)
<span style="color: #000000;">triangle</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">extract</span><span style="color: #0000FF;">(</span><span style="color: #000000;">triangle</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">})</span>
integer s = (i<=2) -- (smudge tests[1..2] by one
<span style="color: #008080;">else</span>
-- pixel to show them better)
<span style="color: #008080;">throw</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"triangle has wrong winding direction"</span><span style="color: #0000FF;">)</span>
draw_triangle(t2,cx+s,cy+s,CD_BLUE)
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
cdCanvasSetForeground(cddbuffer, CD_BLACK)
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
cdCanvasText(cddbuffer,cx+10,cy-40,overlap(t1,t2,0,i=2,i!=8))
<span style="color: #008080;">return</span> <span style="color: #000000;">triangle</span>
if i=4 then
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
cy = 100
cx = 100
<span style="color: #008080;">function</span> <span style="color: #000000;">overlap</span><span style="color: #0000FF;">(</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">t1</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">t2</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">atom</span> <span style="color: #000000;">epsilon</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0.0</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">bool</span> <span style="color: #000000;">allowReversed</span><span style="color: #0000FF;">=</span><span style="color: #004600;">false</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">onBoundary</span><span style="color: #0000FF;">=</span><span style="color: #004600;">true</span><span style="color: #0000FF;">)</span>
else
<span style="color: #000080;font-style:italic;">-- Trangles must be expressed anti-clockwise</span>
cx += 300
<span style="color: #000000;">bReversed</span> <span style="color: #0000FF;">=</span> <span style="color: #004600;">false</span>
end if
<span style="color: #000000;">t1</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">checkWinding</span><span style="color: #0000FF;">(</span><span style="color: #000000;">t1</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">allowReversed</span><span style="color: #0000FF;">)</span>
end for
<span style="color: #000000;">t2</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">checkWinding</span><span style="color: #0000FF;">(</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">allowReversed</span><span style="color: #0000FF;">)</span>
cdCanvasFlush(cddbuffer)
return IUP_DEFAULT
<span style="color: #008080;">for</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">2</span> <span style="color: #008080;">do</span> <span style="color: #000080;font-style:italic;">-- check t1 then t2</span>
end function
<span style="color: #008080;">for</span> <span style="color: #000000;">edge</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">3</span> <span style="color: #008080;">do</span> <span style="color: #000080;font-style:italic;">-- check each edge</span>
 
<span style="color: #004080;">sequence</span> <span style="color: #000000;">p1</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">t1</span><span style="color: #0000FF;">[</span><span style="color: #000000;">edge</span><span style="color: #0000FF;">],</span>
function map_cb(Ihandle ih)
<span style="color: #000000;">p2</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">t1</span><span style="color: #0000FF;">[</span><span style="color: #7060A8;">mod</span><span style="color: #0000FF;">(</span><span style="color: #000000;">edge</span><span style="color: #0000FF;">,</span><span style="color: #000000;">3</span><span style="color: #0000FF;">)+</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span>
cdcanvas = cdCreateCanvas(CD_IUP, ih)
<span style="color: #000080;font-style:italic;">-- Check all points of trangle 2 lay on the external side
cddbuffer = cdCreateCanvas(CD_DBUFFER, cdcanvas)
-- of the edge E. If they do, the triangles do not collide.</span>
cdCanvasSetBackground(cddbuffer, CD_WHITE)
<span style="color: #004080;">integer</span> <span style="color: #000000;">onside</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
return IUP_DEFAULT
<span style="color: #008080;">for</span> <span style="color: #000000;">k</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">3</span> <span style="color: #008080;">do</span>
end function
<span style="color: #004080;">integer</span> <span style="color: #000000;">c</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">compare</span><span style="color: #0000FF;">(</span><span style="color: #000000;">det2D</span><span style="color: #0000FF;">({</span><span style="color: #000000;">p1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">[</span><span style="color: #000000;">k</span><span style="color: #0000FF;">]}),</span><span style="color: #000000;">epsilon</span><span style="color: #0000FF;">)</span>
 
<span style="color: #008080;">if</span> <span style="color: #000000;">onBoundary</span> <span style="color: #008080;">then</span>
procedure main()
<span style="color: #008080;">if</span> <span style="color: #008080;">not</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">c</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
IupOpen()
<span style="color: #008080;">else</span>
<span style="color: #008080;">if</span> <span style="color: #008080;">not</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">c</span><span style="color: #0000FF;"><=</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
canvas = IupCanvas(NULL)
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
IupSetAttribute(canvas, "RASTERSIZE", "1250x300")
<span style="color: #000080;font-style:italic;">-- -- (the following incomprehensible one-liner is equivalent:)
IupSetCallback(canvas, "MAP_CB", Icallback("map_cb"))
-- if compare(det2D({p1,p2,t2[k]}),epsilon)&gt;-onBoundary then exit end if</span>
 
<span style="color: #000000;">onside</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
dlg = IupDialog(canvas,"DIALOGFRAME=YES")
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
IupSetAttribute(dlg, "TITLE", "Triangle overlap")
<span style="color: #008080;">if</span> <span style="color: #000000;">onside</span><span style="color: #0000FF;">=</span><span style="color: #000000;">3</span> <span style="color: #008080;">then</span>
IupSetCallback(canvas, "ACTION", Icallback("redraw_cb"))
<span style="color: #008080;">return</span> <span style="color: #008080;">iff</span><span style="color: #0000FF;">(</span><span style="color: #000000;">onBoundary</span><span style="color: #0000FF;">?</span><span style="color: #008000;">"no overlap"</span><span style="color: #0000FF;">:</span><span style="color: #008000;">"no overlap (no boundary)"</span><span style="color: #0000FF;">)</span>
 
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
IupShowXY(dlg,IUP_CENTER,IUP_CENTER)
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
IupSetAttribute(canvas, "RASTERSIZE", NULL)
<span style="color: #0000FF;">{</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">t1</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">t1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">}</span> <span style="color: #000080;font-style:italic;">-- flip and re-test</span>
IupMainLoop()
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
IupClose()
<span style="color: #008080;">return</span> <span style="color: #008080;">iff</span><span style="color: #0000FF;">(</span><span style="color: #000000;">bReversed</span><span style="color: #0000FF;">?</span><span style="color: #008000;">"overlap (reversed)"</span><span style="color: #0000FF;">:</span><span style="color: #008000;">"overlap"</span><span style="color: #0000FF;">)</span>
end procedure
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
 
main()</lang>
<span style="color: #008080;">function</span> <span style="color: #000000;">redraw_cb</span><span style="color: #0000FF;">(</span><span style="color: #004080;">Ihandle</span> <span style="color: #000080;font-style:italic;">/*ih*/</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">cdCanvasActivate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">cy</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">200</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">cx</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">100</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">triangles</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">sequence</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">t1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">triangles</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span>
<span style="color: #000000;">draw_triangle</span><span style="color: #0000FF;">(</span><span style="color: #000000;">t1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cx</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cy</span><span style="color: #0000FF;">,</span><span style="color: #004600;">CD_RED</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">s</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">i</span><span style="color: #0000FF;"><=</span><span style="color: #000000;">2</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- (smudge tests[1..2] by one
-- pixel to show them better)</span>
<span style="color: #000000;">draw_triangle</span><span style="color: #0000FF;">(</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cx</span><span style="color: #0000FF;">+</span><span style="color: #000000;">s</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cy</span><span style="color: #0000FF;">+</span><span style="color: #000000;">s</span><span style="color: #0000FF;">,</span><span style="color: #004600;">CD_BLUE</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">cdCanvasSetForeground</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span> <span style="color: #004600;">CD_BLACK</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">cdCanvasText</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cx</span><span style="color: #0000FF;">+</span><span style="color: #000000;">10</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cy</span><span style="color: #0000FF;">-</span><span style="color: #000000;">40</span><span style="color: #0000FF;">,</span><span style="color: #000000;">overlap</span><span style="color: #0000FF;">(</span><span style="color: #000000;">t1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">t2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">i</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">8</span><span style="color: #0000FF;">))</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">4</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">cy</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">100</span>
<span style="color: #000000;">cx</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">100</span>
<span style="color: #008080;">else</span>
<span style="color: #000000;">cx</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">300</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #7060A8;">cdCanvasFlush</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">return</span> <span style="color: #004600;">IUP_DEFAULT</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">map_cb</span><span style="color: #0000FF;">(</span><span style="color: #004080;">Ihandle</span> <span style="color: #000000;">ih</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">cdcanvas</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">cdCreateCanvas</span><span style="color: #0000FF;">(</span><span style="color: #004600;">CD_IUP</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">ih</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">cddbuffer</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">cdCreateCanvas</span><span style="color: #0000FF;">(</span><span style="color: #004600;">CD_DBUFFER</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">cdcanvas</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">cdCanvasSetBackground</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cddbuffer</span><span style="color: #0000FF;">,</span> <span style="color: #004600;">CD_WHITE</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">return</span> <span style="color: #004600;">IUP_DEFAULT</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">main</span><span style="color: #0000FF;">()</span>
<span style="color: #7060A8;">IupOpen</span><span style="color: #0000FF;">()</span>
<span style="color: #000000;">canvas</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">IupCanvas</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"RASTERSIZE=1250x300"</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">IupSetCallbacks</span><span style="color: #0000FF;">(</span><span style="color: #000000;">canvas</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">{</span><span style="color: #008000;">"MAP_CB"</span><span style="color: #0000FF;">,</span> <span style="color: #7060A8;">Icallback</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"map_cb"</span><span style="color: #0000FF;">),</span>
<span style="color: #008000;">"ACTION"</span><span style="color: #0000FF;">,</span> <span style="color: #7060A8;">Icallback</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"redraw_cb"</span><span style="color: #0000FF;">)})</span>
<span style="color: #000000;">dlg</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">IupDialog</span><span style="color: #0000FF;">(</span><span style="color: #000000;">canvas</span><span style="color: #0000FF;">,</span><span style="color: #008000;">`RESIZE=NO, TITLE="Triangle overlap"`</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">IupShow</span><span style="color: #0000FF;">(</span><span style="color: #000000;">dlg</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">IupSetAttribute</span><span style="color: #0000FF;">(</span><span style="color: #000000;">canvas</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"RASTERSIZE"</span><span style="color: #0000FF;">,</span> <span style="color: #004600;">NULL</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #7060A8;">platform</span><span style="color: #0000FF;">()!=</span><span style="color: #004600;">JS</span> <span style="color: #008080;">then</span>
<span style="color: #7060A8;">IupMainLoop</span><span style="color: #0000FF;">()</span>
<span style="color: #7060A8;">IupClose</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #000000;">main</span><span style="color: #0000FF;">()</span>
<!--</lang>-->
 
=={{header|Python}}==
Petelomax
7,806

edits

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