nim/env.nim

   1 import tables, types
   2
   3 proc initEnv*(outer: Env = nil, binds, exprs: MalType = nilObj): Env =
   4   result = Env(data: initTable[string, MalType](), outer: outer)
   5
   6   if binds.kind in {List, Vector}:
   7     for i, e in binds.list:
   8       if e.str == "&":
   9         result.data[binds.list[i+1].str] = list(exprs.list[i .. -1])
  10         break
  11       else:
  12         result.data[e.str] = exprs.list[i]
  13
  14 proc set*(e: var Env, key: string, value: MalType): MalType {.discardable.} =
  15   e.data[key] = value
  16   value
  17
  18 proc find*(e: Env, key: string): Env =
  19   if e.data.hasKey(key): return e
  20   if e.outer != nil:     return e.outer.find(key)
  21
  22 proc get*(e: Env, key: string): MalType =
  23   let env = e.find(key)
  24   if env == nil: raise newException(ValueError, "'" & key & "' not found")
  25   env.data[key]