* Builtin function `add' to add integers.

* Put common test functions in tests/lang/lib.nix.

tests/lang/eval-okay-arithmetic.exp

@@ -0,0 +1 @@
+Int(1275)

tests/lang/eval-okay-arithmetic.nix

@@ -0,0 +1,18 @@
+with import ./lib.nix;
+
+let {
+
+  range = first: last: [first] ++ (if first == last then [] else range (builtins.add first 1) last);
+
+  /* Supposedly tail recursive version:
+  
+  range_ = accum: first: last: 
+    if first == last then ([first] ++ accum)
+    else range_ ([first] ++ accum) (builtins.add first 1) last;
+
+  range = range_ [];
+  */
+
+  body = sum (range 1 50);
+
+}

tests/lang/eval-okay-flatten.nix

@@ -1,18 +1,7 @@
+with import ./lib.nix;
+
 let {
 
-  fold = op: nul: list:
-    if list == []
-    then nul
-    else op (builtins.head list) (fold op nul (builtins.tail list));
-
-  concat =
-    fold (x: y: x + y) "";
-    
-  flatten = x:
-    if builtins.isList x
-    then fold (x: y: (flatten x) ++ y) [] x
-    else [x];
-
   l = ["1" "2" ["3" ["4"] ["5" "6"]] "7"];
 
   body = concat (flatten l);

tests/lang/eval-okay-list.nix

@@ -1,13 +1,7 @@
+with import ./lib.nix;
+
 let {
 
-  fold = op: nul: list:
-    if list == []
-    then nul
-    else op (builtins.head list) (fold op nul (builtins.tail list));
-
-  concat =
-    fold (x: y: x + y) "";
-
   body = concat ["foo" "bar" "bla" "test"];
     
 }

tests/lang/eval-okay-map.exp

@@ -1 +1 @@
-List([Call(Function1("x",OpPlus(Var("x"),Str("bar")),Pos("(string)",1,7)),Str("foo")),Call(Function1("x",OpPlus(Var("x"),Str("bar")),Pos("(string)",1,7)),Str("bla")),Call(Function1("x",OpPlus(Var("x"),Str("bar")),Pos("(string)",1,7)),Str("xyzzy"))])
+Str("foobarblabarxyzzybar")

tests/lang/eval-okay-map.nix

@@ -1 +1,3 @@
-map (x: x + "bar") [ "foo" "bla" "xyzzy" ]
+with import ./lib.nix;
+
+concat (map (x: x + "bar") [ "foo" "bla" "xyzzy" ])

tests/lang/lib.nix

@@ -0,0 +1,18 @@
+rec {
+
+  fold = op: nul: list:
+    if list == []
+    then nul
+    else op (builtins.head list) (fold op nul (builtins.tail list));
+
+  concat =
+    fold (x: y: x + y) "";
+
+  flatten = x:
+    if builtins.isList x
+    then fold (x: y: (flatten x) ++ y) [] x
+    else [x];
+
+  sum = fold (x: y: builtins.add x y) 0;
+
+}