swift/step0_repl.swift

   1 //******************************************************************************
   2 // MAL - step 0 - repl
   3 //******************************************************************************
   4 // This file is automatically generated from templates/step.swift. Rather than
   5 // editing it directly, it's probably better to edit templates/step.swift and
   6 // regenerate this file. Otherwise, your change might be lost if/when someone
   7 // else performs that process.
   8 //******************************************************************************
   9
  10 import Foundation
  11
  12 // Parse the string into an AST.
  13 //
  14 private func READ(str: String) -> String {
  15     return str
  16 }
  17
  18 // Walk the AST and completely evaluate it, handling macro expansions, special
  19 // forms and function calls.
  20 //
  21 private func EVAL(ast: String) -> String {
  22     return ast
  23 }
  24
  25 // Convert the value into a human-readable string for printing.
  26 //
  27 private func PRINT(exp: String) -> String {
  28     return exp
  29 }
  30
  31 // Perform the READ and EVAL steps. Useful for when you don't care about the
  32 // printable result.
  33 //
  34 private func RE(text: String) -> String {
  35     let ast = READ(text)
  36     let exp = EVAL(ast)
  37     return exp
  38 }
  39
  40 // Perform the full READ/EVAL/PRINT, returning a printable string.
  41 //
  42 private func REP(text: String) -> String {
  43     let exp = RE(text)
  44     return PRINT(exp)
  45 }
  46
  47 // Perform the full REPL.
  48 //
  49 private func REPL() {
  50     while true {
  51         if let text = _readline("user> ") {
  52             print("\(REP(text))")
  53         } else {
  54             print("")
  55             break
  56         }
  57     }
  58 }
  59
  60 func main() {
  61     load_history_file()
  62     REPL()
  63     save_history_file()
  64 }