samples: add Terra samples

source: https://github.com/zdevito/terra/tree/master/tests

samples/Terra/lazylog.t

@@ -0,0 +1,61 @@
+local function gentrees(depth)
+    local function treetostring(tree)
+        if type(tree) == "string" then return tree
+        elseif tree.rhs then return "(" .. treetostring(tree.lhs) .. " " .. tree.op .. " " .. treetostring(tree.rhs) .. ")"
+        else return "(" .. tree.op .. " " .. treetostring(tree.lhs) .. ")" end
+    end
+    local function gendepth(depth)
+        local trees = {}
+        table.insert(trees, "%s")
+        if depth == 0 then return trees end
+        local subtrees = gendepth(depth - 1)
+        for _,t0 in ipairs(subtrees) do
+            table.insert(trees, { lhs = t0, op = "not" })
+            for _,t1 in ipairs(subtrees) do
+                table.insert(trees, { lhs = t0, rhs = t1, op = "and" })
+                table.insert(trees, { lhs = t0, rhs = t1, op = "or" })
+            end
+        end
+        return trees
+    end
+    local trees = gendepth(depth)
+    local nargs = 2 ^ depth
+    local argassign = "local i0"
+    local targs = "return terra(i0 : bool"
+    local args = {"i0"}
+    for i = 1, nargs - 1 do
+        local arg = "i"..tostring(i)
+        table.insert(args,arg)
+        argassign = argassign .. ", " .. arg
+        targs = targs .. ", " .. arg .. " : bool"
+    end
+    argassign = argassign .. " = ..."
+    targs = targs .. ")"
+    
+    argassign = argassign .. "\nreturn "
+    targs = targs .. "\nreturn "
+    for treeno,t in ipairs(trees) do
+        local line = string.format(treetostring(t),unpack(args))
+        io.write(string.format("\r%3d%% %s",treeno/#trees * 100,line))
+        local lcode = argassign .. line
+        local tcode = targs .. line .. " end"
+        local lfn = assert(loadstring(lcode))
+        local tfn = assert(terralib.loadstring(tcode))()
+        tfn:compile()
+        local states = 2 ^ nargs
+        local actuals = {}
+        local band = bit.band
+        local blshift = bit.lshift
+        for i = 0, states - 1 do
+            for s = 1, nargs do
+                actuals[s] = 0 ~= band(i,blshift(1,s-1))
+            end 
+            local result = lfn(unpack(actuals))
+            local result2 = tfn(unpack(actuals))
+            assert(result == result2)
+        end
+    end
+    io.write("\n")
+end
+
+gentrees(2)