math.extras: adding linspace.

extra/math/extras/extras-docs.factor

@@ -57,3 +57,7 @@ HELP: sinc
 { $values { "x" number } { "y" number } }
 { $description "Returns the " { $link sinc } " function, calculated according to " { $snippet "sin(pi * x) / (pi * x)" } ". The name " { $link sinc } " is short for \"sine cardinal\" or \"sinus cardinalis\"." }
 { $notes { $snippet "0 sinc" } " is the limit value of 1." } ;
+
+HELP: linspace
+{ $values { "from" number } { "to" number } { "points" number } { "seq" sequence } }
+{ $description "Return evenly spaced numbers over a specified interval " { $snippet "[from,to]" } "." } ;

extra/math/extras/extras-tests.factor

@@ -1,7 +1,7 @@
 ! Copyright (C) 2012 John Benediktsson
 ! See http://factorcode.org/license.txt for BSD license
 
-USING: math math.extras math.ranges sequences tools.test ;
+USING: arrays math math.extras math.ranges sequences tools.test ;
 
 IN: math.extras.test
 
@@ -77,3 +77,5 @@ IN: math.extras.test
     { 1 2 3 4 }
     { 0 1 0 0 2 3 }
 } [ { 1 2 1 1 3 4 } unique-indices ] unit-test
+
+{ { 1 10+3/4 20+1/2 30+1/4 40 } } [ 1 40 5 linspace >array ] unit-test

extra/math/extras/extras.factor

@@ -198,3 +198,6 @@ PRIVATE>
 
 : unique-indices ( seq -- unique indices )
     [ members ] keep over dup length iota H{ } zip-as '[ _ at ] map ;
+
+: linspace ( from to points -- seq )
+    1 - [ 2dup swap - ] dip / <range> ;