Lua: all steps and self-hosting.

Also some misc docs/TODO updates.

1 files changed, 88 insertions, 0 deletions

diff --git a/lua/step3_env.lua b/lua/step3_env.lua
new file mode 100755
index 0000000..ed2e62a
--- /dev/null
+++ b/lua/step3_env.lua
@@ -0,0 +1,88 @@
+#!/usr/bin/env lua
+
+local table = require('table')
+
+local readline = require('readline')
+local utils = require('utils')
+local types = require('types')
+local reader = require('reader')
+local printer = require('printer')
+local Env = require('env')
+local List, Vector, HashMap = types.List, types.Vector, types.HashMap
+
+-- read
+function READ(str)
+    return reader.read_str(str)
+end
+
+-- eval
+function eval_ast(ast, env)
+    if types._symbol_Q(ast) then
+        return env:get(ast)
+    elseif types._list_Q(ast) then
+        return List:new(utils.map(function(x) return EVAL(x,env) end,ast))
+    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
+        local new_hm = {}
+        for k,v in pairs(ast) do
+            new_hm[EVAL(k, env)] = EVAL(v, env)
+        end
+        return HashMap:new(new_hm)
+    else
+        return ast
+    end
+end
+
+function EVAL(ast, env)
+    --print("EVAL: "..printer._pr_str(ast,true))
+    if not types._list_Q(ast) then return eval_ast(ast, env) end
+
+    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))
+    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))
+        end
+        return EVAL(a2, let_env)
+    else
+        local args = eval_ast(ast, env)
+        local f = table.remove(args, 1)
+        return f(unpack(args))
+    end
+end
+
+-- print
+function PRINT(exp)
+    return printer._pr_str(exp, true)
+end
+
+-- repl
+local repl_env = Env:new()
+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)
+
+while true do
+    line = readline.readline("user> ")
+    if not line then break end
+    xpcall(function()
+        print(rep(line))
+    end, function(exc)
+        if exc then
+            if types._malexception_Q(exc) then
+                exc = printer._pr_str(exc.val, true)
+            end
+            print("Error: " .. exc)
+            print(debug.traceback())
+        end
+    end)
+end