From d2f33fe305f6a2a4ad2a18f1eafc4e1e4741bd8c Mon Sep 17 00:00:00 2001
From: Drahflow <drahflow@gmx.de>
Date: Mon, 21 Aug 2017 07:52:18 +0200
Subject: Added _' for indexed access to stack

---
 compiler/elymasGlobal.ey | 18 ++++++++++++++++++
 doc/global.md            | 13 +++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/compiler/elymasGlobal.ey b/compiler/elymasGlobal.ey
index cfa58cf..66ab27f 100644
--- a/compiler/elymasGlobal.ey
+++ b/compiler/elymasGlobal.ey
@@ -2056,6 +2056,24 @@
       :retn
     ] /ey_ defv
 
+    # top stack element is an integer index into the stack,
+    # starting with 0 at the one below this index
+    # duplicates the indicated stack element to the top
+    [[
+      /rbx :popqReg
+      /rdx :popqReg
+      63 /rdx :btrqImm8Reg
+      /unboxed :jcLbl8
+      8 /rdx /rdx :movqMemDisp8Reg
+      @unboxed
+
+      8 /rdx /rsp /rdx :movqMemIndexScaleReg
+      /rdx :pushqReg
+
+      /rbx :pushqReg
+      :retn
+    ]] /ey_' defv
+
     # top stack element is a string defining a stack shuffle
     # 0-9: push the thusly numbered element
     #   *: execute top element
diff --git a/doc/global.md b/doc/global.md
index e207973..99dc65c 100644
--- a/doc/global.md
+++ b/doc/global.md
@@ -311,6 +311,19 @@ Duplicates the top stack element.
     0000000000000001
 
 
+`_'`
+---
+
+Takes from the top of the stack an integer. This is used as
+an index into the rest of the stack (starting from top).
+The specified stack element is duplicated to the top of the stack.
+
+    /a /b /c 1 _' dump dump dump dump
+    "b"
+    "c"
+    "b"
+    "a"
+
 `-`
 ---
 
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