RosettaCodeData/Task/Recamans-sequence/PL-I/recamans-sequence.pli

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recaman: procedure options(main);
declare A(0:30) fixed;
/* is X in the first N terms of the Recaman sequence? */
find: procedure(x, n) returns(bit);
declare (x, n, i) fixed;
do i=0 to n-1;
if A(i)=x then return('1'b);
end;
return('0'b);
end find;
/* generate the N'th term of the Recaman sequence */
generate: procedure(n) returns(fixed);
declare n fixed;
if n=0 then
A(0) = 0;
else do;
declare (sub, add) fixed;
sub = A(n-1) - n;
add = A(n-1) + n;
/* A(n-1) - n not positive? */
if sub <= 0 then
A(n) = add;
/* A(n-1) - n already generated? */
else if find(sub, n) then
A(n) = add;
else
A(n) = sub;
end;
return(A(n));
end generate;
declare i fixed;
put skip list('First 15 members:');
do i=0 to 14;
put edit(generate(i)) (F(3));
end;
put skip list('First repeated term: ');
do i=15 repeat(i+1) while(^find(generate(i), i)); end;
put edit('A(',i,') = ',A(i)) (A,F(2),A,F(2));
end recaman;