lerp functions

basis/math/functions/functions-tests.factor

@@ -157,3 +157,8 @@ IN: math.functions.tests
     2135623355842621559
     [ >bignum ] tri@ ^mod
 ] unit-test
+
+[ 1.0  ] [ 1.0 2.5 0.0 lerp ] unit-test
+[ 2.5  ] [ 1.0 2.5 1.0 lerp ] unit-test
+[ 1.75 ] [ 1.0 2.5 0.5 lerp ] unit-test
+

basis/math/functions/functions.factor

@@ -262,3 +262,6 @@ M: real atan fatan ;
     [ drop ] [ dup 0 < [ - 1- ] [ - ] if ] if ; foldable
 
 : ceiling ( x -- y ) neg floor neg ; foldable
+
+: lerp ( a b t -- a_t ) [ over - ] dip * + ; inline
+

basis/math/vectors/vectors-tests.factor

@@ -9,3 +9,8 @@ USING: math.vectors tools.test ;
 [ 5 ] [ { 1 2 } norm-sq ] unit-test
 [ 13 ] [ { 2 3 } norm-sq ] unit-test
 
+[ { 1.0  2.5  } ] [ { 1.0 2.5 } { 2.5 1.0 } 0.0 vnlerp ] unit-test 
+[ { 2.5  1.0  } ] [ { 1.0 2.5 } { 2.5 1.0 } 1.0 vnlerp ] unit-test 
+[ { 1.75 1.75 } ] [ { 1.0 2.5 } { 2.5 1.0 } 0.5 vnlerp ] unit-test 
+
+[ { 1.75 2.125 } ] [ { 1.0 2.5 } { 2.5 1.0 } { 0.5 0.25 } vlerp ] unit-test 

basis/math/vectors/vectors.factor

@@ -32,6 +32,12 @@ IN: math.vectors
 : set-axis ( u v axis -- w )
     [ [ zero? 2over ? ] dip swap nth ] map-index 2nip ;
 
+: vlerp ( a b t -- a_t )
+    [ lerp ] 3map ;
+
+: vnlerp ( a b t -- a_t )
+    [ lerp ] curry 2map ;
+
 HINTS: vneg { array } ;
 HINTS: norm-sq { array } ;
 HINTS: norm { array } ;
@@ -50,3 +56,6 @@ HINTS: v/ { array array } ;
 HINTS: vmax { array array } ;
 HINTS: vmin { array array } ;
 HINTS: v. { array array } ;
+
+HINTS: vlerp { array array array } ;
+HINTS: vnlerp { array array object } ;