1 USING: arrays kernel sequences vectors math math.vectors namespaces
2 shuffle splitting sequences.lib math.order ;
5 ! Polynomials are vectors with the highest powers on the right:
6 ! { 1 1 0 1 } -> 1 + x + x^3
9 : powers ( n x -- seq )
10 #! Output sequence has n elements, { 1 x x^2 x^3 ... }
11 <array> 1 [ * ] accumulate nip ;
14 : 2pad-left ( p p n -- p p ) 0 [ pad-left swap ] 2keep pad-left swap ;
15 : 2pad-right ( p p n -- p p ) 0 [ pad-right swap ] 2keep pad-right swap ;
16 : pextend ( p p -- p p ) 2dup [ length ] bi@ max 2pad-right ;
17 : pextend-left ( p p -- p p ) 2dup [ length ] bi@ max 2pad-left ;
18 : unempty ( seq -- seq ) [ { 0 } ] when-empty ;
19 : 2unempty ( seq seq -- seq seq ) [ unempty ] bi@ ;
22 : p= ( p p -- ? ) pextend = ;
25 dup length 1 = [ [ zero? ] trim-right ] unless ;
27 : 2ptrim ( p p -- p p ) [ ptrim ] bi@ ;
28 : p+ ( p p -- p ) pextend v+ ;
29 : p- ( p p -- p ) pextend v- ;
30 : n*p ( n p -- n*p ) n*v ;
33 : pextend-conv ( p p -- p p )
34 #! extend to: p_m + p_n - 1
35 2dup [ length ] bi@ + 1- 2pad-right [ >vector ] bi@ ;
38 #! Multiply two polynomials.
39 2unempty pextend-conv <reversed> dup length
40 [ over length pick <slice> pick [ * ] 2map sum ] map 2nip reverse ;
47 : p/mod-setup ( p p -- p p n )
50 dup 1 < [ drop 1 ] when
51 [ over length + 0 pad-left pextend ] keep 1+ ;
53 : /-last ( seq seq -- a )
54 #! divide the last two numbers in the sequences
57 : (p/mod) ( p p -- p p )
61 dup pop* swap rest-slice ;
65 : p/mod ( a b -- / mod )
66 p/mod-setup [ [ (p/mod) ] times ] V{ } make
67 reverse nip swap 2ptrim pextend ;
69 : (pgcd) ( b a y x -- a d )
73 tuck p/mod >r pick p* swap >r swapd p- r> r> (pgcd)
77 swap V{ 0 } clone V{ 1 } clone 2swap (pgcd) [ >array ] bi@ ;
80 #! Polynomial derivative.
81 dup length v* { 0 } ?head drop ;
83 : polyval ( p x -- p[x] )
84 #! Evaluate a polynomial.
85 >r dup length r> powers v. ;