Racket: add steps0-A. Self-hosting.

- Some additioanl tests.
- Split step9 tests into optional but self-hosting requirements
  (metadata on functions) and other optional (conj, metadata on
  collections).

12 files changed, 873 insertions, 0 deletions

diff --git a/docs/steps/step0_repl.txt b/docs/steps/step0_repl.txt
new file mode 100644
index 0000000..db31e58
--- /dev/null
+++ b/docs/steps/step0_repl.txt
@@ -0,0 +1,11 @@
+--- step0_repl ----------------------------------
+READ(str): return str
+
+EVAL(ast,any): return ast
+
+PRINT(exp): return exp
+
+rep(str): return PRINT(EVAL(READ(str),""))
+
+main loop: println(rep(readline("user> ")))
+
diff --git a/docs/steps/step1_read_print.txt b/docs/steps/step1_read_print.txt
new file mode 100644
index 0000000..3a0fd7c
--- /dev/null
+++ b/docs/steps/step1_read_print.txt
@@ -0,0 +1,14 @@
+--- step1_read_print ----------------------------
+import reader, printer
+
+READ(str): return reader.read_str(str)
+
+EVAL(ast,env): return ast
+
+PRINT(exp): return printer.pr_str(exp)
+
+rep(str): return PRINT(EVAL(READ(str),""))
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
diff --git a/docs/steps/step2_eval.txt b/docs/steps/step2_eval.txt
new file mode 100644
index 0000000..beb5500
--- /dev/null
+++ b/docs/steps/step2_eval.txt
@@ -0,0 +1,25 @@
+--- step2_eval ----------------------------------
+import types, reader, printer
+
+READ(str): return reader.read_str(str)
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return lookup(env, ast) OR raise "'" + ast + "' not found"
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+    if not list?(ast): return eval_ast(ast, env)
+    f, args = eval_ast(ast, env)
+    return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = {'+: add_fn, ...}
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
diff --git a/docs/steps/step3_env.txt b/docs/steps/step3_env.txt
new file mode 100644
index 0000000..a1de572
--- /dev/null
+++ b/docs/steps/step3_env.txt
@@ -0,0 +1,38 @@
+--- step3_env -----------------------------------
+import types, reader, printer, env
+
+READ(str): return reader.read_str(str)
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        return EVAL(ast[2], ...)
+      _default_:    f, args = eval_ast(ast, env)
+                    return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+repl_env.set('+, add_fn)
+    ...
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null)
+    data = hash_map()
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
diff --git a/docs/steps/step4_if_fn_do.txt b/docs/steps/step4_if_fn_do.txt
new file mode 100644
index 0000000..805d9b1
--- /dev/null
+++ b/docs/steps/step4_if_fn_do.txt
@@ -0,0 +1,76 @@
+--- step4_if_fn_do ------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        return EVAL(ast[2], ...)
+      'do:          return eval_ast(rest(ast), env)[-1]
+      'if:          return EVAL(EVAL(ast[1], env) ? ast[2] : ast[3], env)
+      'fn*:         return (...a) -> EVAL(ast[2], new Env(env, ast[1], a))
+      _default_:    f, args = eval_ast(ast, env)
+                    return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+
+;; core.mal: defined using the language itself
+rep("(def! not (fn* (a) (if a false true)))")
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'empty?:   empty?,
+      'count:    count}
diff --git a/docs/steps/step5_tco.txt b/docs/steps/step5_tco.txt
new file mode 100644
index 0000000..30e2a46
--- /dev/null
+++ b/docs/steps/step5_tco.txt
@@ -0,0 +1,78 @@
+--- step5_tco -----------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+
+;; core.mal: defined using the language itself
+rep("(def! not (fn* (a) (if a false true)))")
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'empty?:   empty?,
+      'count:    count}
diff --git a/docs/steps/step6_file.txt b/docs/steps/step6_file.txt
new file mode 100644
index 0000000..bccf8fa
--- /dev/null
+++ b/docs/steps/step6_file.txt
@@ -0,0 +1,85 @@
+--- step6_file ----------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
+repl_env.set('*ARGV*, cmdline_args[1..])
+
+;; core.mal: defined using the language itself
+rep("(def! not (fn* (a) (if a false true)))")
+rep("(def! load-file (fn* (f) ...))")
+
+if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+      'read-string: read_str,
+      'slurp     read-file,
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'empty?:   empty?,
+      'count:    count}
diff --git a/docs/steps/step7_quote.txt b/docs/steps/step7_quote.txt
new file mode 100644
index 0000000..c166257
--- /dev/null
+++ b/docs/steps/step7_quote.txt
@@ -0,0 +1,92 @@
+--- step7_quote ---------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+pair?(ast): return ... // true if non-empty sequence
+quasiquote(ast): return ... // quasiquote
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'quote:       return ast[1]
+      'quasiquote:  ast = quasiquote(ast[1]) // TCO
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
+repl_env.set('*ARGV*, cmdline_args[1..])
+
+;; core.mal: defined using the language itself
+rep("(def! not (fn* (a) (if a false true)))")
+rep("(def! load-file (fn* (f) ...))")
+
+if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+      'read-string: read_str,
+      'slurp     read-file,
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'cons:     (a) -> concat([a[0]], a[1]),
+      'concat:   (a) -> reduce(concat, [], a),
+      'empty?:   empty?,
+      'count:    count}
diff --git a/docs/steps/step8_macros.txt b/docs/steps/step8_macros.txt
new file mode 100644
index 0000000..da68191
--- /dev/null
+++ b/docs/steps/step8_macros.txt
@@ -0,0 +1,102 @@
+--- step8_macros --------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+pair?(ast): return ... // true if non-empty sequence
+quasiquote(ast): return ... // quasiquote
+
+macro?(ast, env): return ... // true if macro function
+macroexpand(ast, env): return ... // recursive macro expansion
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'quote:       return ast[1]
+      'quasiquote:  ast = quasiquote(ast[1]) // TCO
+      'defmacro!:   return ... // like def!, but set macro property
+      'macroexpand: return macroexpand(ast[1], env)
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
+repl_env.set('*ARGV*, cmdline_args[1..])
+
+;; core.mal: defined using the language itself
+rep("(def! not (fn* (a) (if a false true)))")
+rep("(def! load-file (fn* (f) ...))")
+rep("(defmacro! cond (fn* (& xs) ...))")
+rep("(defmacro! or (fn* (& xs) ...))")
+
+if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+      'read-string: read_str,
+      'slurp     read-file,
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'cons:     (a) -> concat([a[0]], a[1]),
+      'concat:   (a) -> reduce(concat, [], a),
+      'nth:      (a) -> a[0][a[1]] OR raise "nth: index out of range",
+      'first:    (a) -> a[0][0] OR nil,
+      'rest:     (a) -> a[0][1..] OR list(),
+      'empty?:   empty?,
+      'count:    count}
diff --git a/docs/steps/step9_try.txt b/docs/steps/step9_try.txt
new file mode 100644
index 0000000..f0bb5c9
--- /dev/null
+++ b/docs/steps/step9_try.txt
@@ -0,0 +1,109 @@
+--- step9_try -----------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+pair?(ast): return ... // true if non-empty sequence
+quasiquote(ast): return ... // quasiquote
+
+macro?(ast, env): return ... // true if macro function
+macroexpand(ast, env): return ... // recursive macro expansion
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'quote:       return ast[1]
+      'quasiquote:  ast = quasiquote(ast[1]) // TCO
+      'defmacro!:   return ... // like def!, but set macro property
+      'macroexpand: return macroexpand(ast[1], env)
+      'try*:        return ... // try/catch native and malval exceptions
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
+repl_env.set('*ARGV*, cmdline_args[1..])
+
+;; core.mal: defined using the language itself
+rep("(def! not (fn* (a) (if a false true)))")
+rep("(def! load-file (fn* (f) ...))")
+rep("(defmacro! cond (fn* (& xs) ...))")
+rep("(defmacro! or (fn* (& xs) ...))")
+
+if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
+
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'throw:    throw,
+
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol:   symbol,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+      'read-string: read_str,
+      'readline: readline,
+      'slurp     read-file,
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'cons:     (a) -> concat([a[0]], a[1]),
+      'concat:   (a) -> reduce(concat, [], a),
+      'nth:      (a) -> a[0][a[1]] OR raise "nth: index out of range",
+      'first:    (a) -> a[0][0] OR nil,
+      'rest:     (a) -> a[0][1..] OR list(),
+      'empty?:   empty?,
+      'count:    count,
+      'apply:    apply,
+      'map:      map}
diff --git a/docs/steps/stepA_interop.txt b/docs/steps/stepA_interop.txt
new file mode 100644
index 0000000..9657468
--- /dev/null
+++ b/docs/steps/stepA_interop.txt
@@ -0,0 +1,112 @@
+--- step9_try -----------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+pair?(ast): return ... // true if non-empty sequence
+quasiquote(ast): return ... // quasiquote
+
+macro?(ast, env): return ... // true if macro function
+macroexpand(ast, env): return ... // recursive macro expansion
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'quote:       return ast[1]
+      'quasiquote:  ast = quasiquote(ast[1]) // TCO
+      'defmacro!:   return ... // like def!, but set macro property
+      'macroexpand: return macroexpand(ast[1], env)
+      'try*:        return ... // try/catch native and malval exceptions
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
+repl_env.set('*ARGV*, cmdline_args[1..])
+
+;; core.mal: defined using the language itself
+rep("(def! *host-language* \"racket\")")
+rep("(def! not (fn* (a) (if a false true)))")
+rep("(def! load-file (fn* (f) ...))")
+rep("(defmacro! cond (fn* (& xs) ...))")
+rep("(defmacro! or (fn* (& xs) ...))")
+
+if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
+
+rep("(println (str \"Mal [\" *host-language* \"]\"))")
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'throw:    throw,
+
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol:   symbol,
+      'symbol?:  symbol?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+      'read-string: read_str,
+      'readline: readline,
+      'slurp     read-file,
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+      'time-ms   cur-epoch-millis,
+
+      'list:     list,
+      'list?:    list?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+
+      'cons:     (a) -> concat([a[0]], a[1]),
+      'concat:   (a) -> reduce(concat, [], a),
+      'nth:      (a) -> a[0][a[1]] OR raise "nth: index out of range",
+      'first:    (a) -> a[0][0] OR nil,
+      'rest:     (a) -> a[0][1..] OR list(),
+      'empty?:   empty?,
+      'count:    count,
+      'apply:    apply,
+      'map:      map}
diff --git a/docs/steps/stepA_interop2.txt b/docs/steps/stepA_interop2.txt
new file mode 100644
index 0000000..1273411
--- /dev/null
+++ b/docs/steps/stepA_interop2.txt
@@ -0,0 +1,131 @@
+--- step9_try -----------------------------------
+import types, reader, printer, env, core
+
+READ(str): return reader.read_str(str)
+
+pair?(ast): return ... // true if non-empty sequence
+quasiquote(ast): return ... // quasiquote
+
+macro?(ast, env): return ... // true if macro function
+macroexpand(ast, env): return ... // recursive macro expansion
+
+eval_ast(ast,env):
+  switch type(ast):
+    symbol:      return env.get(ast)
+    list,vector: return ast.map((x) -> EVAL(x,env))
+    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
+    _default_:   return ast
+
+EVAL(ast,env):
+  while true:
+    if not list?(ast): return eval_ast(ast, env)
+    switch ast[0]:
+      'def!:        return env.set(ast[1], EVAL(ast[2], env))
+      'let*:        env = ...; ast = ast[2] // TCO
+      'quote:       return ast[1]
+      'quasiquote:  ast = quasiquote(ast[1]) // TCO
+      'defmacro!:   return ... // like def!, but set macro property
+      'macroexpand: return macroexpand(ast[1], env)
+      'try*:        return ... // try/catch native and malval exceptions
+      'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
+      'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
+      'fn*:         return new MalFunc(...)
+      _default_:    f, args = eval_ast(ast, env)
+                    if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
+                    else:                return apply(f, args)
+
+PRINT(exp): return printer.pr_str(exp)
+
+repl_env = new Env()
+rep(str): return PRINT(EVAL(READ(str),repl_env))
+
+;; core.EXT: defined using Racket
+core.ns.map((k,v) -> (repl_env.set(k, v)))
+repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
+repl_env.set('*ARGV*, cmdline_args[1..])
+
+;; core.mal: defined using the language itself
+rep("(def! *host-language* \"racket\")")
+rep("(def! not (fn* (a) (if a false true)))")
+rep("(def! load-file (fn* (f) ...))")
+rep("(defmacro! cond (fn* (& xs) ...))")
+rep("(defmacro! or (fn* (& xs) ...))")
+
+if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
+
+rep("(println (str \"Mal [\" *host-language* \"]\"))")
+main loop:
+  try:      println(rep(readline("user> ")))
+  catch e:  println("Error: ", e)
+
+--- env module ----------------------------------
+class Env (outer=null,binds=[],exprs=[])
+    data = hash_map()
+    foreach b, i in binds:
+      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
+      else: data[binds[i]] = exprs[i]
+  set(k,v): return data.set(k,v)
+  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
+  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
+    
+--- core module ---------------------------------
+ns = {'=:        equal?,
+      'throw:    throw,
+
+      'nil?:     nil?,
+      'true?:    true?,
+      'false?:   false?,
+      'symbol:   symbol,
+      'symbol?:  symbol?,
+      'keyword:  keyword,
+      'keyword?: keyword?,
+
+      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
+      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
+      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
+      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
+      'read-string: read_str,
+      'readline: readline,
+      'slurp     read-file,
+
+      '<:        lt,
+      '<=:       lte,
+      '>:        gt,
+      '>=:       gte,
+      '+:        add,
+      '-:        sub,
+      '*:        mult,
+      '/:        div,
+
+      'list:     list,
+      'list?:    list?,
+      'vector:   vector,
+      'vector?:  vector?,
+      'hash-map: hash_map,
+      'map?:     hash_map?,
+      'assoc:    assoc,
+      'dissoc:   dissoc,
+      'get:      get,
+      'contains?: contains?,
+      'keys:     keys,
+      'vals:     vals,
+
+      'sequential? sequential?,
+      'cons:     (a) -> concat([a[0]], a[1]),
+      'concat:   (a) -> reduce(concat, [], a),
+      'nth:      (a) -> a[0][a[1]] OR raise "nth: index out of range",
+      'first:    (a) -> a[0][0] OR nil,
+      'rest:     (a) -> a[0][1..] OR list(),
+      'empty?:   empty?,
+      'count:    count,
+      'apply:    apply,
+      'map:      map,
+      'conj:     conj,
+
+      'meta:     (a) -> a[0].meta,
+      'with-meta: (a) -> a[0].with_meta(a[1]),
+      'atom:     (a) -> new Atom(a[0]),
+      'atom?:    (a) -> type(a[0]) == "atom",
+      'deref:    (a) -> a[0].val,
+      'reset!:   (a) -> a[0].val = a[1],
+      'swap!:    swap!}