1 files changed, 80 insertions, 0 deletions
diff --git a/matlab/step3_env.m b/matlab/step3_env.m
new file mode 100644
index 0000000..6ac6426
--- /dev/null
+++ b/matlab/step3_env.m
@@ -0,0 +1,80 @@
+function step3_env(varargin), main(varargin), end
+
+% read
+function ret = READ(str)
+    ret = reader.read_str(str);
+end
+
+% eval
+function ret = eval_ast(ast, env)
+    switch class(ast)
+    case 'types.Symbol'
+        ret = env.get(ast);
+    case 'cell'
+        ret = {};
+        for i=1:length(ast)
+            ret{end+1} = EVAL(ast{i}, env);
+        end
+    otherwise
+        ret = ast;
+    end
+end
+
+function ret = EVAL(ast, env)
+    if ~iscell(ast),
+        ret = eval_ast(ast, env);
+        return;
+    end
+
+    % apply
+    if isa(ast{1},'types.Symbol')
+        a1sym = ast{1}.name;
+    else
+        a1sym = '_@$fn$@_';
+    end
+    switch (a1sym)
+    case 'def!'
+        ret = env.set(ast{2}, EVAL(ast{3}, env));
+    case 'let*'
+        let_env = Env(env);
+        for i=1:2:length(ast{2})
+            let_env.set(ast{2}{i}, EVAL(ast{2}{i+1}, let_env));
+        end
+        ret = EVAL(ast{3}, let_env);
+    otherwise
+        el = eval_ast(ast, env);
+        f = el{1};
+        args = el(2:end);
+        ret = f(args{:});
+    end
+end
+
+% print
+function ret = PRINT(ast)
+    ret = printer.pr_str(ast, true);
+end
+
+% REPL
+function ret = rep(str, env)
+    ret = PRINT(EVAL(READ(str), env));
+end
+
+function main(args)
+    repl_env = Env(false);
+    repl_env.set(types.Symbol('+'), @(a,b) a+b);
+    repl_env.set(types.Symbol('-'), @(a,b) a-b);
+    repl_env.set(types.Symbol('*'), @(a,b) a*b);
+    repl_env.set(types.Symbol('/'), @(a,b) floor(a/b));
+
+    %cleanObj = onCleanup(@() disp('*** here1 ***'));
+    while (true)
+        line = input('user> ', 's');
+        if strcmp(strtrim(line),''), continue, end
+        try
+            fprintf('%s\n', rep(line, repl_env));
+        catch err
+            fprintf('Error: %s\n', err.message);
+            fprintf('%s\n', getReport(err, 'extended'));
+        end
+    end
+end