1 files changed, 60 insertions, 0 deletions
diff --git a/ps/env.ps b/ps/env.ps
new file mode 100644
index 0000000..b8752af
--- /dev/null
+++ b/ps/env.ps
@@ -0,0 +1,60 @@
+(in env.ps\n) print
+
+% outer binds exprs -> env_new -> new_env
+/env_new { 3 dict begin
+    %(in env_new\n) print
+    /exprs exch dup _sequential? { /data get }{ pop [ ] } ifelse def
+    /binds exch dup _sequential? { /data get }{ pop [ ] } ifelse def
+    /outer exch def
+    << 
+        /__outer__ outer
+        0 1 binds length 1 sub {
+            /idx exch def
+            binds idx get (&) eq { %if &
+                binds idx 1 add get % key
+                exprs idx   exprs length idx sub   getinterval % value
+                _list_from_array
+                exit
+            } if
+            binds idx get % key
+            exprs idx get % value
+        } for
+    >>
+end } def
+
+/env_find { 2 dict begin
+    /key exch def
+    /env exch def
+    env key known { %if key in env
+        env
+    }{ env /__outer__ get null ne { %elseif __outer__ not null
+        env /__outer__ get   key env_find
+    }{ %else
+        null
+    } ifelse } ifelse
+end } def
+
+/env_set { 4 dict begin
+    dup
+    /func? exch xcheck def % executable function
+    /val exch cvlit def
+    /key exch def
+    /env exch def
+    env key val func? { cvx } if put
+    val func? { cvx } if
+end } def
+
+/env_get { 2 dict begin
+    /key exch def
+    /env exch def
+    env key env_find
+    dup null eq {
+        (')
+        key dup length string cvs
+        (' not found)
+        concatenate concatenate
+        _throw
+    }{
+        key get
+    } ifelse
+end } def