1 IN: polynomials-internals
2 USING: arrays kernel sequences vectors math math-internals namespaces arrays
5 ! Polynomials are vectors with the highest powers on the right:
6 ! { 1 1 0 1 } -> 1 + x + x^3
9 : 2pad-left ( p p n -- p p ) 0 [ pad-left swap ] 2keep pad-left swap ;
10 : 2pad-right ( p p n -- p p ) 0 [ pad-right swap ] 2keep pad-right swap ;
11 : pextend ( p p -- p p ) 2dup [ length ] 2apply max 2pad-right ;
12 : pextend-left ( p p -- p p ) 2dup [ length ] 2apply max 2pad-left ;
13 : unempty ( seq -- seq ) dup empty? [ drop { 0 } ] when ;
14 : 2unempty ( seq seq -- seq seq ) [ unempty ] 2apply ;
17 : p= ( p p -- ? ) pextend = ;
19 : ptrim ( p -- p ) [ zero? ] rtrim* ;
21 : 2ptrim ( p p -- p p ) [ ptrim ] 2apply ;
22 : p+ ( p p -- p ) pextend v+ ;
23 : p- ( p p -- p ) pextend v- ;
24 : n*p ( n p -- n*p ) n*v ;
27 : pextend-conv ( p p -- p p )
28 #! extend to: p_m + p_n - 1
29 2dup [ length ] 2apply + 1- 2pad-right [ >vector ] 2apply ;
32 #! Multiply two polynomials.
33 2unempty pextend-conv <reversed> dup length
34 [ over length pick <slice> pick [ * ] 2map sum ] map 2nip reverse ;
39 IN: polynomials-internals
41 : pop-front ( seq -- seq )
44 : /-last ( seq seq -- a )
45 #! divide the last two numbers in the sequences
48 : p/mod-setup ( p p -- p p n )
49 2ptrim 2dup [ length ] 2apply - dup 1 < [ drop 1 ] when
50 dup >r over length + 0 pad-left pextend r> 1+ ;
53 2dup /-last 2dup , n*p swapd p- >vector dup pop drop swap pop-front ;
57 p/mod-setup [ [ (p/mod) ] times ] V{ } make
58 reverse nip swap 2ptrim pextend ;
60 : (pgcd) ( b a y x -- a d )
64 tuck p/mod >r pick p* swap >r swapd p- r> r> (pgcd)
68 swap V{ 0 } clone V{ 1 } clone 2swap (pgcd) [ >array ] 2apply ;
71 #! Polynomial derivative.
72 dup length v* { 0 } ?head drop ;
74 : polyval ( p x -- p[x] )
75 #! Evaluate a polynomial.
76 >r dup length r> powers v. ;