matlab/step2_eval.m

   1 function step2_eval(varargin), main(varargin), end
   2
   3 % read
   4 function ret = READ(str)
   5     ret = reader.read_str(str);
   6 end
   7
   8 % eval
   9 function ret = eval_ast(ast, env)
  10     switch class(ast)
  11     case 'types.Symbol'
  12         ret = env(ast.name);
  13     case 'cell'
  14         ret = {};
  15         for i=1:length(ast)
  16             ret{end+1} = EVAL(ast{i}, env);
  17         end
  18     otherwise
  19         ret = ast;
  20     end
  21 end
  22
  23 function ret = EVAL(ast, env)
  24     if ~iscell(ast),
  25         ret = eval_ast(ast, env);
  26         return;
  27     end
  28
  29     % apply
  30     el = eval_ast(ast, env);
  31     f = el{1};
  32     args = el(2:end);
  33     ret = f(args{:});
  34 end
  35
  36 % print
  37 function ret = PRINT(ast)
  38     ret = printer.pr_str(ast, true);
  39 end
  40
  41 % REPL
  42 function ret = rep(str, env)
  43     ret = PRINT(EVAL(READ(str), env));
  44 end
  45
  46 function main(args)
  47     repl_env = containers.Map();
  48     repl_env('+') = @(a,b) a+b;
  49     repl_env('-') = @(a,b) a-b;
  50     repl_env('*') = @(a,b) a*b;
  51     repl_env('/') = @(a,b) floor(a/b);
  52
  53     %cleanObj = onCleanup(@() disp('*** here1 ***'));
  54     while (true)
  55         line = input('user> ', 's');
  56         if strcmp(strtrim(line),''), continue, end
  57         try
  58             fprintf('%s\n', rep(line, repl_env));
  59         catch err
  60             fprintf('Error: %s\n', err.message);
  61             fprintf('%s\n', getReport(err, 'extended'));
  62         end
  63     end
  64 end