Talk:Find the intersection of two lines: Difference between revisions
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Walterpachl (talk | contribs) m (well, waiting for other opinions) |
m (→a REXX version of a REXX version: included comments that were added to REXX version 2, added more comments.) |
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{{trans|REXX (version 2)}} |
{{trans|REXX (version 2)}} |
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<lang rexx>/*REXX program finds (possibly) the intersection of two lines (with diagnostic errors).*/ |
<lang rexx>/*REXX program finds (possibly) the intersection of two lines (with diagnostic errors).*/ |
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say iSect( 4 0 6 10 0 3 10 7 ) |
say iSect( 4 0 6 10 0 3 10 7 ) |
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say iSect( 0 0 0 10 0 3 10 7 ) |
say iSect( 0 0 0 10 0 3 10 7 ) |
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say iSect( 0 0 0 10 0 3 10 7 ) |
say iSect( 0 0 0 10 0 3 10 7 ) |
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say iSect( 0 0 0 1 1 0 1 7 ) |
say iSect( 0 0 0 1 1 0 1 7 ) |
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say iSect( 0 0 0 0 0 3 10 7 ) |
say iSect( 0 0 0 0 0 3 10 7 ) |
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say iSect( 0 0 3 3 0 0 6 6 ) |
say iSect( 0 0 3 3 0 0 6 6 ) |
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say iSect( 0 0 3 3 0 1 6 7 ) |
say iSect( 0 0 3 3 0 1 6 7 ) |
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say iSect( 0 0 3 3 8 8 8 8 ) |
say iSect( 0 0 3 3 8 8 8 8 ) |
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exit |
exit /* ═══a═══ ═══b═══ ═══c═══ ═══c═══ stick a fork in it, we're all done. */ |
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/*──────────────────────────────────────────────────────────────────────────────────────*/ |
/*──────────────────────────────────────────────────────────────────────────────────────*/ |
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iSect: procedure; parse arg xa ya xb yb xc yc xd yd |
iSect: procedure; parse arg xa ya xb yb xc yc xd yd |
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@ident= 'lines AB and CD are identical' /*literal to help shorten a line*/ |
@ident= 'lines AB and CD are identical' /*literal to help shorten a line*/ |
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@paral= 'lines AB and CD are parallel' |
@paral= 'lines AB and CD are parallel' /* " " " " " " */ |
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$=. /*the |
$=. /*the intersection or error msg.*/ |
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if xa=xb then do |
if xa=xb then do /*is AB a vertical line? */ |
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k1=. |
k1=. /*the slope is infinite. */ |
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x1=xa |
x1=xa /*the X's intersection is XA */ |
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if ya=yb then $= 'points A and B are identical' |
if ya=yb then $= 'points A and B are identical' |
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end |
end |
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else do |
else do /*AB isn't a vertical line. */ |
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k1=(yb-ya) / (xb-xa) |
k1=(yb-ya) / (xb-xa) /*compute the slope of AB */ |
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d1=ya - k1 * xa |
d1=ya - k1 * xa /*calc. intersection with Y axis*/ |
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end |
end |
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if xc=xd then do |
if xc=xd then do /*is CD a vertical line? */ |
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k2=. |
k2=. /*the slope is infinite. */ |
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x2=xc |
x2=xc /*the C's intersection is XC */ |
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if yc=yd then $= 'points C and D are identical' |
if yc=yd then $= 'points C and D are identical' |
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end |
end |
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else do |
else do /*CD isn't a vertical line. */ |
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k2=(yd-yc) / (xd-xc) |
k2=(yd-yc) / (xd-xc) /*compute the slope of CD */ |
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d2=yc - k2 * xc |
d2=yc - k2 * xc /*calc. intersection with Y axis*/ |
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end |
end |
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if $=. then do |
if $=. then do /*no special case so far ··· */ |
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if k1=. |
if k1=. then if k2=. then if x1=x2 then $=@ident /*identical. */ |
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else $=@paral /*parallel. */ |
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else do |
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x=x1 /*use X1 */ |
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y=k2 * x + d2 /*Y from CD */ |
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end |
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else if k2=. then do /*vertical CD*/ |
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x=x2 /*X from CD */ |
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y=k1 * x + d1 /*Y from AB */ |
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end |
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else if k1=k2 then if d1=d2 then $= @ident |
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else $= @paral |
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else do /*normal.*/ |
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x=(d2-d1) / (k1-k2) |
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y=k1 * x + d1 |
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end /*normal line*/ |
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end |
end |
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if $=. then $= 'intersection is at (' || x","y')' |
if $=. then $= 'intersection is at (' || x","y')' /*$ ¬defined?*/ |
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info= 'a=('xa","ya') b=('xb","yb') |
info=left( 'a=('xa","ya')', 12) left( 'b=('xb","yb')', 12), |
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left( 'c=('xc","yc')', 12) left( 'd=('xd","yd')', 12) |
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return left(info, max(51, length(info) ) ) ' ───► ' $ /*return str.*/</lang> |
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{{out|output|text= when using the default |
{{out|output|text= when using the default inputs:}} |
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<pre> |
<pre> |
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a=(4,0) b=(6,10) c=(0,3) d=(10,7) |
a=(4,0) b=(6,10) c=(0,3) d=(10,7) ───► intersection is at (5,5) |
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a=(0,0) b=(0,10) c=(0,3) d=(10,7) |
a=(0,0) b=(0,10) c=(0,3) d=(10,7) ───► intersection is at (0,3) |
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a=(0,0) b=(0,10) c=(0,3) d=(10,7) |
a=(0,0) b=(0,10) c=(0,3) d=(10,7) ───► intersection is at (0,3) |
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a=(0,0) b=(0,1) c=(1,0) d=(1,7) |
a=(0,0) b=(0,1) c=(1,0) d=(1,7) ───► lines AB and CD are parallel |
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a=(0,0) b=(0,0) c=(0,3) d=(10,7) |
a=(0,0) b=(0,0) c=(0,3) d=(10,7) ───► points A and B are identical |
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a=(0,0) b=(3,3) c=(0,0) d=(6,6) |
a=(0,0) b=(3,3) c=(0,0) d=(6,6) ───► lines AB and CD are identical |
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a=(0,0) b=(3,3) c=(0,1) d=(6,7) |
a=(0,0) b=(3,3) c=(0,1) d=(6,7) ───► lines AB and CD are parallel |
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a=(0,0) b=(3,3) c=(8,8) d=(8,8) |
a=(0,0) b=(3,3) c=(8,8) d=(8,8) ───► points C and D are identical |
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</pre> |
</pre> |
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============================================================================================== |
============================================================================================== |
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: If I were to translate many of the Rexx programs of GS to my liking I'd be busy for months. |
: If I were to translate many of the Rexx programs of GS to my liking I'd be busy for months. |
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::: There is no reason to take it personally. It wasn't meant as a criticism, it is just another version in a different style, albeit a fair number of (style) differences. <u>Everybody's</u> code can be improved (as least, the style can be changed). In this case, I elided a few superfluous statements, which, in my opinion, didn't add anything to the REXX program or make it easier to understand/peruse. I didn't appreciate your style of capitalization, misaligned DO-END statements (and the intervening/encapsulating REXX statements), split IF-THEN clauses, and much more. But, that's only my opinion and preferences, I merely added a version that I found easier to read and understand (and I hoped others will appreciate this version), and I also removed superfluous DO-END blocks and such. Note that this re-written REXX version was added in the '' |
::: There is no reason to take it personally. It wasn't meant as a criticism, it is just another version in a different style, albeit a fair number of (style) differences. <u>Everybody's</u> code can be improved (as least, the style can be changed). In this case, I elided a few superfluous statements, which, in my opinion, didn't add anything to the REXX program or make it easier to understand/peruse. I didn't appreciate your style of capitalization, misaligned DO-END statements (and the intervening/encapsulating REXX statements), split IF-THEN clauses, and much more. But, that's only my opinion and preferences, I merely added a version that I found easier to read and understand (and I hoped others will appreciate this version), and I also removed superfluous DO-END blocks and such. Note that this re-written REXX version was added in the ''discussion'' section, not on the ''page'' section so as to not clutter up the main page. I found that that particular REXX version was so difficult to follow and understand (the IF logic) with all the multiple misaligned DO-END and compound IF THEN-ELSE statements. The version (above) that I re-wrote speaks to style and understandability. There are many styles to write REXX programs in, and this is just one of them. Nobody's style is everybody's cup of tea. -- [[User:Gerard Schildberger|Gerard Schildberger]] ([[User talk:Gerard Schildberger|talk]]) 08:22, 19 May 2017 (UTC) |
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