diff options
Diffstat (limited to 'lua/stepA_mal.lua')
| -rwxr-xr-x | lua/stepA_mal.lua | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/lua/stepA_mal.lua b/lua/stepA_mal.lua new file mode 100755 index 0000000..db31789 --- /dev/null +++ b/lua/stepA_mal.lua @@ -0,0 +1,205 @@ +#!/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 core = require('core') +local List, Vector, HashMap = types.List, types.Vector, types.HashMap + +-- read +function READ(str) + return reader.read_str(str) +end + +-- eval +function is_pair(x) + return types._sequential_Q(x) and #x > 0 +end + +function quasiquote(ast) + if not is_pair(ast) then + return types.List:new({types.Symbol:new("quote"), ast}) + elseif types._symbol_Q(ast[1]) and ast[1].val == 'unquote' then + return ast[2] + elseif is_pair(ast[1]) and + types._symbol_Q(ast[1][1]) and + ast[1][1].val == 'splice-unquote' then + return types.List:new({types.Symbol:new("concat"), + ast[1][2], + quasiquote(ast:slice(2))}) + else + return types.List:new({types.Symbol:new("cons"), + quasiquote(ast[1]), + quasiquote(ast:slice(2))}) + end +end + +function is_macro_call(ast, env) + if types._list_Q(ast) and + types._symbol_Q(ast[1]) and + env:find(ast[1]) then + local f = env:get(ast[1]) + return types._malfunc_Q(f) and f.ismacro + end +end + +function macroexpand(ast, env) + while is_macro_call(ast, env) do + local mac = env:get(ast[1]) + ast = mac.fn(unpack(ast:slice(2))) + end + return ast +end + +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) + while true do + --print("EVAL: "..printer._pr_str(ast,true)) + if not types._list_Q(ast) then return eval_ast(ast, env) end + + -- apply list + ast = macroexpand(ast, env) + if not types._list_Q(ast) then return ast end + + 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)) + 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 + env = let_env + ast = a2 -- TCO + elseif 'quote' == a0sym then + return a1 + elseif 'quasiquote' == a0sym then + ast = quasiquote(a1) -- TCO + elseif 'defmacro!' == a0sym then + local mac = EVAL(a2, env) + mac.ismacro = true + return env:set(a1, mac) + elseif 'macroexpand' == a0sym then + return macroexpand(a1, env) + elseif 'try*' == a0sym then + local exc, result = nil, nil + xpcall(function() + result = EVAL(a1, env) + end, function(err) + exc = err + end) + if exc ~= nil then + if types._malexception_Q(exc) then + exc = exc.val + end + if a2 and a2[1].val == 'catch*' then + result = EVAL(a2[3], Env:new(env, {a2[2]}, {exc})) + else + types.throw(exc) + end + end + return result + elseif 'do' == a0sym then + local el = eval_ast(ast:slice(2,#ast-1), env) + ast = ast[#ast] -- TCO + elseif 'if' == a0sym then + local cond = EVAL(a1, env) + if cond == types.Nil or cond == false then + if a3 then ast = a3 else return types.Nil end -- TCO + else + ast = a2 -- TCO + end + elseif 'fn*' == a0sym then + return types.MalFunc:new(function(...) + return EVAL(a2, Env:new(env, a1, arg)) + end, a2, env, a1) + else + local args = eval_ast(ast, env) + local f = table.remove(args, 1) + if types._malfunc_Q(f) then + ast = f.ast + env = Env:new(f.env, f.params, args) -- TCO + else + return f(unpack(args)) + end + end + 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 + +-- core.lua: defined using Lua +for k,v in pairs(core.ns) do + repl_env:set(types.Symbol:new(k), v) +end +repl_env:set(types.Symbol:new('eval'), + function(ast) return EVAL(ast, repl_env) end) +repl_env:set(types.Symbol:new('*ARGV*'), types.List:new(types.slice(arg,2))) + +-- core.mal: defined using mal +rep("(def! *host-language* \"lua\")") +rep("(def! not (fn* (a) (if a false true)))") +rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))") +rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))") +rep("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))") + +function print_exception(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 + +if #arg > 0 and arg[1] == "--raw" then + readline.raw = true + table.remove(arg,1) +end + +if #arg > 0 then + xpcall(function() rep("(load-file \""..arg[1].."\")") end, + print_exception) + os.exit(0) +end + +rep("(println (str \"Mal [\" *host-language* \"]\"))") +while true do + line = readline.readline("user> ") + if not line then break end + xpcall(function() print(rep(line)) end, + print_exception) +end |