lua: simplify and debug environments

Use plain LUA strings as keys in environments. Search outers environments with a loop. Remove the now unneeded Env:find trick. Let DEBUG-EVAL show the contents of all outer environments but repl_env.
asarhaddon · Aug 26, 2024 · f64b53c · f64b53c
1 parent 5a35cb6
commit f64b53c
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Showing 9 changed files with 145 additions and 120 deletions.
diff --git a/impls/lua/env.lua b/impls/lua/env.lua
@@ -1,9 +1,12 @@
 local table = require('table')
 local types = require('types')
+local printer = require('printer')
 
 local Env = {}
 
 function Env:new(outer, binds, exprs)
+    -- binds is a MAL sequence of MAL symbols
+    -- exprs is an LUA table of MAL forms
     local data = {}
     local newObj = {outer = outer, data = data}
     self.__index = self
@@ -22,27 +25,35 @@ function Env:new(outer, binds, exprs)
     end
     return setmetatable(newObj, self)
 end
-function Env:find(sym)
-    if self.data[sym.val] ~= nil then
-        return self
-    else
-        if self.outer ~= nil then
-            return self.outer:find(sym)
-        else
-            return nil
-        end
+
+function Env:get(sym)
+    -- sym is an LUA string
+    -- returns nil if the key is not found
+    local env = self
+    local result
+    while true do
+        result = env.data[sym]
+        if result ~= nil then return result end
+        env = env.outer
+        if env == nil then return nil end
     end
 end
+
 function Env:set(sym,val)
-    self.data[sym.val] = val
+    -- sym is an LUA string
+    self.data[sym] = val
     return val
 end
-function Env:get(sym)
-    local env = self:find(sym)
-    if env then
-        return env.data[sym.val]
-    else
-        types.throw("'"..sym.val.."' not found")
+
+function Env:debug()
+    local env = self
+    while env.outer ~=nil do
+        line = '  ENV:'
+        for k, v in pairs(env.data) do
+            line = line .. ' ' .. k .. '=' .. printer._pr_str(v)
+        end
+        print(line)
+        env = env.outer
     end
 end
 

diff --git a/impls/lua/step3_env.lua b/impls/lua/step3_env.lua
@@ -19,17 +19,18 @@ end
 
 function EVAL(ast, env)
 
-    local dbgeval_key = types.Symbol:new("DEBUG-EVAL")
-    local dbgeval_env = env:find(dbgeval_key)
-    if dbgeval_env then
-        local dbgeval = dbgeval_env:get(dbgeval_key)
-        if dbgeval ~= types.Nil and dbgeval ~= false then
-            print("EVAL: " .. printer._pr_str(ast, true))
-        end
+    local dbgeval = env:get("DEBUG-EVAL")
+    if dbgeval ~= nil and dbgeval ~= types.Nil and dbgeval ~= false then
+        print("EVAL: " .. printer._pr_str(ast, true))
+        env:debug()
     end
 
     if types._symbol_Q(ast) then
-        return env:get(ast)
+        local result = env:get(ast.val)
+        if result == nil then
+            types.throw("'" .. ast.val .. "' not found")
+        end
+        return result
     elseif types._vector_Q(ast) then
         return Vector:new(utils.map(function(x) return EVAL(x,env) end,ast))
     elseif types._hash_map_Q(ast) then
@@ -45,11 +46,11 @@ function EVAL(ast, env)
     local a0,a1,a2 = ast[1], ast[2],ast[3]
     local a0sym = types._symbol_Q(a0) and a0.val or ""
     if 'def!' == a0sym then
-        return env:set(a1, EVAL(a2, env))
+        return env:set(a1.val, EVAL(a2, env))
     elseif 'let*' == a0sym then
         local let_env = Env:new(env)
         for i = 1,#a1,2 do
-            let_env:set(a1[i], EVAL(a1[i+1], let_env))
+            let_env:set(a1[i].val, EVAL(a1[i+1], let_env))
         end
         return EVAL(a2, let_env)
     else
@@ -71,10 +72,10 @@ function rep(str)
     return PRINT(EVAL(READ(str),repl_env))
 end
 
-repl_env:set(types.Symbol:new('+'), function(a,b) return a+b end)
-repl_env:set(types.Symbol:new('-'), function(a,b) return a-b end)
-repl_env:set(types.Symbol:new('*'), function(a,b) return a*b end)
-repl_env:set(types.Symbol:new('/'), function(a,b) return math.floor(a/b) end)
+repl_env:set('+', function(a,b) return a+b end)
+repl_env:set('-', function(a,b) return a-b end)
+repl_env:set('*', function(a,b) return a*b end)
+repl_env:set('/', function(a,b) return math.floor(a/b) end)
 
 if #arg > 0 and arg[1] == "--raw" then
     readline.raw = true

diff --git a/impls/lua/step4_if_fn_do.lua b/impls/lua/step4_if_fn_do.lua
@@ -20,17 +20,18 @@ end
 
 function EVAL(ast, env)
 
-    local dbgeval_key = types.Symbol:new("DEBUG-EVAL")
-    local dbgeval_env = env:find(dbgeval_key)
-    if dbgeval_env then
-        local dbgeval = dbgeval_env:get(dbgeval_key)
-        if dbgeval ~= types.Nil and dbgeval ~= false then
-            print("EVAL: " .. printer._pr_str(ast, true))
-        end
+    local dbgeval = env:get("DEBUG-EVAL")
+    if dbgeval ~= nil and dbgeval ~= types.Nil and dbgeval ~= false then
+        print("EVAL: " .. printer._pr_str(ast, true))
+        env:debug()
     end
 
     if types._symbol_Q(ast) then
-        return env:get(ast)
+        local result = env:get(ast.val)
+        if result == nil then
+            types.throw("'" .. ast.val .. "' not found")
+        end
+        return result
     elseif types._vector_Q(ast) then
         return Vector:new(utils.map(function(x) return EVAL(x,env) end,ast))
     elseif types._hash_map_Q(ast) then
@@ -46,11 +47,11 @@ function EVAL(ast, env)
     local a0,a1,a2,a3 = ast[1], ast[2],ast[3],ast[4]
     local a0sym = types._symbol_Q(a0) and a0.val or ""
     if 'def!' == a0sym then
-        return env:set(a1, EVAL(a2, env))
+        return env:set(a1.val, EVAL(a2, env))
     elseif 'let*' == a0sym then
         local let_env = Env:new(env)
         for i = 1,#a1,2 do
-            let_env:set(a1[i], EVAL(a1[i+1], let_env))
+            let_env:set(a1[i].val, EVAL(a1[i+1], let_env))
         end
         return EVAL(a2, let_env)
     elseif 'do' == a0sym then
@@ -88,7 +89,7 @@ end
 
 -- core.lua: defined using Lua
 for k,v in pairs(core.ns) do
-    repl_env:set(types.Symbol:new(k), v)
+    repl_env:set(k, v)
 end
 
 -- core.mal: defined using mal

diff --git a/impls/lua/step5_tco.lua b/impls/lua/step5_tco.lua
@@ -20,17 +20,19 @@ end
 
 function EVAL(ast, env)
   while true do
-    local dbgeval_key = types.Symbol:new("DEBUG-EVAL")
-    local dbgeval_env = env:find(dbgeval_key)
-    if dbgeval_env then
-        local dbgeval = dbgeval_env:get(dbgeval_key)
-        if dbgeval ~= types.Nil and dbgeval ~= false then
-            print("EVAL: " .. printer._pr_str(ast, true))
-        end
+
+    local dbgeval = env:get("DEBUG-EVAL")
+    if dbgeval ~= nil and dbgeval ~= types.Nil and dbgeval ~= false then
+        print("EVAL: " .. printer._pr_str(ast, true))
+        env:debug()
     end
 
     if types._symbol_Q(ast) then
-        return env:get(ast)
+        local result = env:get(ast.val)
+        if result == nil then
+            types.throw("'" .. ast.val .. "' not found")
+        end
+        return result
     elseif types._vector_Q(ast) then
         return Vector:new(utils.map(function(x) return EVAL(x,env) end,ast))
     elseif types._hash_map_Q(ast) then
@@ -46,11 +48,11 @@ function EVAL(ast, env)
     local a0,a1,a2,a3 = ast[1], ast[2],ast[3],ast[4]
     local a0sym = types._symbol_Q(a0) and a0.val or ""
     if 'def!' == a0sym then
-        return env:set(a1, EVAL(a2, env))
+        return env:set(a1.val, EVAL(a2, env))
     elseif 'let*' == a0sym then
         local let_env = Env:new(env)
         for i = 1,#a1,2 do
-            let_env:set(a1[i], EVAL(a1[i+1], let_env))
+            let_env:set(a1[i].val, EVAL(a1[i+1], let_env))
         end
         env = let_env
         ast = a2 -- TCO
@@ -95,7 +97,7 @@ end
 
 -- core.lua: defined using Lua
 for k,v in pairs(core.ns) do
-    repl_env:set(types.Symbol:new(k), v)
+    repl_env:set(k, v)
 end
 
 -- core.mal: defined using mal

diff --git a/impls/lua/step6_file.lua b/impls/lua/step6_file.lua
@@ -20,17 +20,19 @@ end
 
 function EVAL(ast, env)
   while true do
-    local dbgeval_key = types.Symbol:new("DEBUG-EVAL")
-    local dbgeval_env = env:find(dbgeval_key)
-    if dbgeval_env then
-        local dbgeval = dbgeval_env:get(dbgeval_key)
-        if dbgeval ~= types.Nil and dbgeval ~= false then
-            print("EVAL: " .. printer._pr_str(ast, true))
-        end
+
+    local dbgeval = env:get("DEBUG-EVAL")
+    if dbgeval ~= nil and dbgeval ~= types.Nil and dbgeval ~= false then
+        print("EVAL: " .. printer._pr_str(ast, true))
+        env:debug()
     end
 
     if types._symbol_Q(ast) then
-        return env:get(ast)
+        local result = env:get(ast.val)
+        if result == nil then
+            types.throw("'" .. ast.val .. "' not found")
+        end
+        return result
     elseif types._vector_Q(ast) then
         return Vector:new(utils.map(function(x) return EVAL(x,env) end,ast))
     elseif types._hash_map_Q(ast) then
@@ -46,11 +48,11 @@ function EVAL(ast, env)
     local a0,a1,a2,a3 = ast[1], ast[2],ast[3],ast[4]
     local a0sym = types._symbol_Q(a0) and a0.val or ""
     if 'def!' == a0sym then
-        return env:set(a1, EVAL(a2, env))
+        return env:set(a1.val, EVAL(a2, env))
     elseif 'let*' == a0sym then
         local let_env = Env:new(env)
         for i = 1,#a1,2 do
-            let_env:set(a1[i], EVAL(a1[i+1], let_env))
+            let_env:set(a1[i].val, EVAL(a1[i+1], let_env))
         end
         env = let_env
         ast = a2 -- TCO
@@ -95,11 +97,11 @@ end
 
 -- core.lua: defined using Lua
 for k,v in pairs(core.ns) do
-    repl_env:set(types.Symbol:new(k), v)
+    repl_env:set(k, v)
 end
-repl_env:set(types.Symbol:new('eval'),
+repl_env:set('eval',
              function(ast) return EVAL(ast, repl_env) end)
-repl_env:set(types.Symbol:new('*ARGV*'), types.List:new(types.slice(arg,2)))
+repl_env:set('*ARGV*', types.List:new(types.slice(arg,2)))
 
 -- core.mal: defined using mal
 rep("(def! not (fn* (a) (if a false true)))")

diff --git a/impls/lua/step7_quote.lua b/impls/lua/step7_quote.lua
@@ -52,17 +52,19 @@ end
 
 function EVAL(ast, env)
   while true do
-    local dbgeval_key = types.Symbol:new("DEBUG-EVAL")
-    local dbgeval_env = env:find(dbgeval_key)
-    if dbgeval_env then
-        local dbgeval = dbgeval_env:get(dbgeval_key)
-        if dbgeval ~= types.Nil and dbgeval ~= false then
-            print("EVAL: " .. printer._pr_str(ast, true))
-        end
+
+    local dbgeval = env:get("DEBUG-EVAL")
+    if dbgeval ~= nil and dbgeval ~= types.Nil and dbgeval ~= false then
+        print("EVAL: " .. printer._pr_str(ast, true))
+        env:debug()
     end
 
     if types._symbol_Q(ast) then
-        return env:get(ast)
+        local result = env:get(ast.val)
+        if result == nil then
+            types.throw("'" .. ast.val .. "' not found")
+        end
+        return result
     elseif types._vector_Q(ast) then
         return Vector:new(utils.map(function(x) return EVAL(x,env) end,ast))
     elseif types._hash_map_Q(ast) then
@@ -78,11 +80,11 @@ function EVAL(ast, env)
     local a0,a1,a2,a3 = ast[1], ast[2],ast[3],ast[4]
     local a0sym = types._symbol_Q(a0) and a0.val or ""
     if 'def!' == a0sym then
-        return env:set(a1, EVAL(a2, env))
+        return env:set(a1.val, EVAL(a2, env))
     elseif 'let*' == a0sym then
         local let_env = Env:new(env)
         for i = 1,#a1,2 do
-            let_env:set(a1[i], EVAL(a1[i+1], let_env))
+            let_env:set(a1[i].val, EVAL(a1[i+1], let_env))
         end
         env = let_env
         ast = a2 -- TCO
@@ -131,11 +133,11 @@ end
 
 -- core.lua: defined using Lua
 for k,v in pairs(core.ns) do
-    repl_env:set(types.Symbol:new(k), v)
+    repl_env:set(k, v)
 end
-repl_env:set(types.Symbol:new('eval'),
+repl_env:set('eval',
              function(ast) return EVAL(ast, repl_env) end)
-repl_env:set(types.Symbol:new('*ARGV*'), types.List:new(types.slice(arg,2)))
+repl_env:set('*ARGV*', types.List:new(types.slice(arg,2)))
 
 -- core.mal: defined using mal
 rep("(def! not (fn* (a) (if a false true)))")