Nim: step3

diff --git a/nim/env.nim b/nim/env.nim
new file mode 100644 (file)
index 0000000..616c817
--- /dev/null
+++ b/nim/env.nim
@@ -0,0 +1,20 @@
+import tables, types
+
+type Env* = ref object
+  data: Table[string, MalType]
+  outer: Env
+
+proc initEnv*: Env = Env(data: initTable[string, MalType]())
+
+proc set*(e: var Env, key: string, value: MalType): MalType {.discardable.} =
+  e.data[key] = value
+  value
+
+proc find(e: Env, key: string): Env =
+  if e.data.hasKey(key): return e
+  if e.outer != nil:     return e.outer.find(key)
+
+proc get*(e: Env, key: string): MalType =
+  let env = e.find(key)
+  if env == nil: raise newException(ValueError, "'" & key & "' not found")
+  env.data[key]

diff --git a/nim/step3_env.nim b/nim/step3_env.nim
new file mode 100644 (file)
index 0000000..9da4af4
--- /dev/null
+++ b/nim/step3_env.nim
@@ -0,0 +1,73 @@
+import rdstdin, tables, sequtils, types, reader, printer, env
+
+proc read(str: string): MalType = str.read_str
+
+proc eval(ast: MalType, env: var Env): MalType
+
+proc eval_ast(ast: MalType, env: var Env): MalType =
+  case ast.kind
+  of Symbol:
+    result = env.get(ast.symbol)
+  of List:
+    result = list ast.list.mapIt(MalType, it.eval(env))
+  of Vector:
+    result = vector ast.vector.mapIt(MalType, it.eval(env))
+  of HashMap:
+    result = hash_map()
+    for k, v in ast.hash_map.pairs:
+      result.hash_map[k] = v.eval(env)
+  else:
+    result = ast
+
+proc eval(ast: MalType, env: var Env): MalType =
+  case ast.kind
+  of List:
+    let
+      a0 = ast.list[0]
+      a1 = ast.list[1]
+      a2 = ast.list[2]
+
+    case a0.symbol
+    of "def!":
+      result = env.set(a1.symbol, a2.eval(env))
+    of "let*":
+      var letEnv: Env
+      letEnv.deepCopy(env)
+      case a1.kind
+      of List:
+        for i in countup(0, a1.list.high, 2):
+          letEnv.set(a1.list[i].symbol, a1.list[i+1].eval(letEnv))
+      of Vector:
+        for i in countup(0, a1.vector.high, 2):
+          letEnv.set(a1.vector[i].symbol, a1.vector[i+1].eval(letEnv))
+      else: discard
+      result = a2.eval(letEnv)
+    else:
+      let el = ast.eval_ast(env)
+      result = el.list[0].fun(el.list[1 .. -1])
+  else:
+    result = ast.eval_ast(env)
+
+proc print(exp: MalType): string = exp.pr_str
+
+template wrapNumberFun(op: expr): expr =
+  fun proc(xs: varargs[MalType]): MalType = number op(xs[0].number, xs[1].number)
+
+var repl_env = initEnv()
+
+repl_env.set("+", wrapNumberFun(`+`))
+repl_env.set("-", wrapNumberFun(`-`))
+repl_env.set("*", wrapNumberFun(`*`))
+repl_env.set("/", wrapNumberFun(`div`))
+#repl_env.set("/", wrapNumberFun(proc(x,y: int): int = int(x.float / y.float)))
+
+proc rep(str: string): string =
+  str.read.eval(repl_env).print
+
+while true:
+  try:
+    let line = readLineFromStdin("user> ")
+    echo line.rep
+  except:
+    echo getCurrentExceptionMsg()
+    echo getCurrentException().getStackTrace()