factor/library/math/vectors.factor

! Copyright (C) 2005 Slava Pestov.
! See http://factor.sf.net/license.txt for BSD license.
IN: math
USING: arrays generic kernel sequences ;

! Vectors
: vneg ( v -- v ) [ neg ] map ;

: n*v ( n v -- v ) [ * ] map-with ;
: v*n ( v n -- v ) swap n*v ;
: n/v ( n v -- v ) [ / ] map-with ;
: v/n ( v n -- v ) swap [ swap / ] map-with ;

: v+   ( v v -- v ) [ + ] 2map ;
: v-   ( v v -- v ) [ - ] 2map ;
: v*   ( v v -- v ) [ * ] 2map ;
: v/   ( v v -- v ) [ / ] 2map ;
: vmax ( v v -- v ) [ max ] 2map ;
: vmin ( v v -- v ) [ min ] 2map ;

: sum ( v -- n ) 0 [ + ] reduce ;
: product ( v -- n ) 1 [ * ] reduce ;

: set-axis ( x y axis -- v )
    2dup v* >r >r drop dup r> v* v- r> v+ ;

: v. ( v v -- x )
    #! Dot product.
    0 [ * + ] 2reduce ;

: norm-sq ( v -- n ) 0 [ absq + ] reduce ;

: norm ( vec -- n )
    #! Length of a vector.
    norm-sq sqrt ;

: normalize ( vec -- uvec )
    #! Unit vector with same direction as vec.
    dup norm v/n ;