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Calkin-Wilf sequence: Difference between revisions
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(Added solution for Little Man Computer) |
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83116/51639 is at index 123456789.
</pre>
=={{header|Forth}}==
{{works with|gforth|0.7.3}}
<lang forth>\ Calkin-Wilf sequence
: frac. swap . ." / " . ;
: cw-next ( num den -- num den ) 2dup / over * 2* over + rot - ;
: cw-seq ( n -- )
1 1 rot
0 do
cr 2dup frac. cw-next
loop 2drop ;
variable index
variable bit-state
variable bit-position
: r2cf-next ( num1 den1 -- num2 den2 u ) swap over >r s>d r> sm/rem ;
: n2bitlength ( n -- )
bit-state @ if
1 swap lshift 1- bit-position @ lshift index +!
else drop then ;
: index-init true bit-state ! 0 bit-position ! 0 index ! ;
: index-build ( n -- )
dup n2bitlength bit-position +! bit-state @ invert bit-state ! ;
: index-finish ( n 0 -- ) 2drop -1 bit-position +! 1 index-build ;
: cw-index ( num den -- )
index-init
begin r2cf-next index-build dup 0<> while repeat
index-finish ;
: cw-demo
20 cw-seq
cr 83116 51639 2dup frac. cw-index index @ . ;
cw-demo</lang>
{{out}}
<pre>1 / 1
1 / 2
2 / 1
1 / 3
3 / 2
2 / 3
3 / 1
1 / 4
4 / 3
3 / 5
5 / 2
2 / 5
5 / 3
3 / 4
4 / 1
1 / 5
5 / 4
4 / 7
7 / 3
3 / 8
83116 / 51639 123456789 ok</pre>
=={{header|FreeBASIC}}==
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