+ LuaMacro

1 files changed, 90 insertions, 0 deletions

diff --git a/Tools/LuaMacro/macro/ifelse.lua b/Tools/LuaMacro/macro/ifelse.lua
new file mode 100644
index 0000000..3d5a0df
--- /dev/null
+++ b/Tools/LuaMacro/macro/ifelse.lua
@@ -0,0 +1,90 @@
+local M = require 'macro'
+
+local function eval (expr,was_expr)
+    expr = tostring(expr)
+    if was_expr then expr = "return "..expr end
+    local chunk = M.assert(loadstring(expr))
+    local ok, res = pcall(chunk)
+    if not ok then M.error("error evaluating "..res) end
+    return res
+end
+
+local function eval_line (get,was_expr)
+    local args = get:line()
+    return eval(args,was_expr)
+end
+
+local function grab (get)
+    local ilevel = 0
+    while true do
+        local t,v = get()
+        while t ~= '@' do t = get() end
+        t,v = get()
+        if v == 'if' then
+            ilevel = ilevel + 1
+        else -- 'end','elseif','else'
+            if ilevel > 0 and v == 'end' then
+                ilevel = ilevel - 1
+            elseif ilevel == 0 then return '@'..v end
+        end
+    end
+end
+
+M.define('@',function(get,put)
+    local t,v = get()
+--~     print('got',t,v)
+    return put:iden(v..'_')
+end)
+
+local ifstack,push,pop = {},table.insert,table.remove
+
+local function push_if (res)
+--~     print 'push'
+    push(ifstack, not (res==false or res==nil))
+end
+
+local function pop_if ()
+--~     print 'pop'
+    pop(ifstack)
+end
+
+M.define('if_',function(get)
+    local res = eval_line(get,true)
+    push_if(res)
+    if not res then
+        return grab(get)
+    end
+end)
+
+M.define('elseif_',function(get)
+    local res
+    if ifstack[#ifstack] then
+        res = false
+    else
+        res = eval_line(get,true)
+        pop_if()
+        push_if(res)
+    end
+    if not res then
+        return grab(get)
+    end
+end)
+
+M.define('else_',function(get)
+    if #ifstack == 0 then M.error("mismatched else") end
+    if ifstack[#ifstack] then
+        return grab(get)
+    end
+end)
+
+M.define('end_',function(get)
+    pop_if()
+end)
+
+M.define('let_',function(get)
+    eval_line(get)
+end)
+
+M.define('eval_(X)',function(X)
+    return tostring(eval(X,true))
+end)