From fb2538a946263baed3dfce1776243cfdb5557303 Mon Sep 17 00:00:00 2001
From: Alexander Iljin <ajsoft@yandex.ru>
Date: Fri, 13 Jan 2017 01:58:52 +0300
Subject: [PATCH] charts.lines: add calc-y

---
 lines/lines-tests.factor | 4 ++++
 lines/lines.factor       | 1 +
 2 files changed, 5 insertions(+)

diff --git a/lines/lines-tests.factor b/lines/lines-tests.factor
index 6361ca6350..c2d693016b 100644
--- a/lines/lines-tests.factor
+++ b/lines/lines-tests.factor
@@ -4,6 +4,10 @@ USING: tools.test charts.lines charts.lines.private ;
 IN: charts.lines.tests
 
 { -2/3 } [ { 1 3 } { -2 5 } calc-line-slope ] unit-test
+{ 3 } [ -2/3 1 { 1 3 } calc-y ] unit-test
+{ 5 } [ -2/3 -2 { 1 3 } calc-y ] unit-test
+{ 3 } [ -2/3 1 { -2 5 } calc-y ] unit-test
+{ 5 } [ -2/3 -2 { -2 5 } calc-y ] unit-test
 
 { { } }
 [ { } { } clip-data ] unit-test
diff --git a/lines/lines.factor b/lines/lines.factor
index f8e0700cca..3e9c7a21d2 100644
--- a/lines/lines.factor
+++ b/lines/lines.factor
@@ -62,6 +62,7 @@ TUPLE: line < gadget color data ;
 !    } 2&& ;
 
 : calc-line-slope ( point1 point2 -- slope ) v- first2 swap / ;
+: calc-y ( slope x point -- y ) first2 [ - * ] dip + ;
 
 : clip-by-first ( min,max pairs -- pairs' )
     2dup first-in-bounds? [