RosettaCodeData/Task/Modular-inverse/Phix/modular-inverse.phix

(phixonline)-->
 <span style="color: #008080;">function</span> <span style="color: #000000;">mul_inv</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">a</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">)</span>
     <span style="color: #008080;">if</span> <span style="color: #000000;">n</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">n</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">n</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #008080;">if</span> <span style="color: #000000;">a</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">a</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">n</span> <span style="color: #0000FF;">-</span> <span style="color: #7060A8;">mod</span><span style="color: #0000FF;">(-</span><span style="color: #000000;">a</span><span style="color: #0000FF;">,</span><span style="color: #000000;">n</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #004080;">integer</span> <span style="color: #000000;">t</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span><span style="color: #0000FF;">,</span>  <span style="color: #000000;">nt</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">1</span><span style="color: #0000FF;">,</span>
             <span style="color: #000000;">r</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">,</span>  <span style="color: #000000;">nr</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">a</span><span style="color: #0000FF;">;</span>
     <span style="color: #008080;">while</span> <span style="color: #000000;">nr</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">do</span>
         <span style="color: #004080;">integer</span> <span style="color: #000000;">q</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">floor</span><span style="color: #0000FF;">(</span><span style="color: #000000;">r</span><span style="color: #0000FF;">/</span><span style="color: #000000;">nr</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;">nt</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">nt</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">-</span><span style="color: #000000;">q</span><span style="color: #0000FF;">*</span><span style="color: #000000;">nt</span><span style="color: #0000FF;">}</span>
         <span style="color: #0000FF;">{</span><span style="color: #000000;">r</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">nr</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">nr</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">r</span><span style="color: #0000FF;">-</span><span style="color: #000000;">q</span><span style="color: #0000FF;">*</span><span style="color: #000000;">nr</span><span style="color: #0000FF;">}</span>
     <span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
     <span style="color: #008080;">if</span> <span style="color: #000000;">r</span><span style="color: #0000FF;">></span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span> <span style="color: #008080;">return</span> <span style="color: #008000;">"a is not invertible"</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #008080;">if</span> <span style="color: #000000;">t</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">t</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">n</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #008080;">return</span> <span style="color: #000000;">t</span>
 <span style="color: #008080;">end</span> <span style="color: #008080;">function</span>

 <span style="color: #0000FF;">?</span><span style="color: #000000;">mul_inv</span><span style="color: #0000FF;">(</span><span style="color: #000000;">42</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2017</span><span style="color: #0000FF;">)</span>
 <span style="color: #0000FF;">?</span><span style="color: #000000;">mul_inv</span><span style="color: #0000FF;">(</span><span style="color: #000000;">40</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">1</span><span style="color: #0000FF;">)</span>
 <span style="color: #0000FF;">?</span><span style="color: #000000;">mul_inv</span><span style="color: #0000FF;">(</span><span style="color: #000000;">52</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">217</span><span style="color: #0000FF;">)</span>  <span style="color: #000080;font-style:italic;">/* Pari semantics for negative modulus */</span>
 <span style="color: #0000FF;">?</span><span style="color: #000000;">mul_inv</span><span style="color: #0000FF;">(-</span><span style="color: #000000;">486</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">217</span><span style="color: #0000FF;">)</span>
 <span style="color: #0000FF;">?</span><span style="color: #000000;">mul_inv</span><span style="color: #0000FF;">(</span><span style="color: #000000;">40</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">2018</span><span style="color: #0000FF;">)</span>
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