Shoelace formula for polygonal area: Difference between revisions
add RPL
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=={{header|RPL}}==
{| class="wikitable"
! RPL code
! Comment
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≪ DUP SIZE → points n
≪ points 1 GET OBJ→ →V2 { 2 1 } RDM
n 1 '''FOR''' j
points j GET OBJ→ →V2 1 COL+ -1 '''STEP'''
0 1 n '''FOR''' j
OVER j DUP n + 2 + SUB DET + '''NEXT'''
ABS 2 / SWAP DROP
≫ ≫ <span style="color:blue">''''SHOEL''''</span> STO
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<span style="color:blue">'''SHOEL'''</span> ''( { (vertices) } → area ) ''
initialise matrix with (x1, y1)
add n columns with (xj, yj)
sum n 2x2 determinants along the matrix
finalize calculation, clean stack
return area
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{(3,4) (5,11) (12,8) (9,5) (5,6)} <span style="color:blue">'''SHOEL'''</span>
{{out}}
<pre>
1: 30
</pre>
=={{header|Ruby}}==
<syntaxhighlight lang="ruby">
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