Hy A Lisp the Compiles to Python... AST @agentultra http://agentultra.com https://www.github.com/agentultra Sunday, 11 August, 13 

http://goo.gl/6yPnmm Sunday, 11 August, 13 

http://goo.gl/6yPnmm Sunday, 11 August, 13 

=> (import [sh [cat grep wc]]) => (-> (cat "/usr/share/dict/words") (grep "-E" "^hy") (wc "-l")) 210 (-> (read) (eval) (print) (loop)) Sunday, 11 August, 13 

Python AST • Incredibly useful • Woefully under-documented • Considered by many to be black magic • Is essentially what Python is Sunday, 11 August, 13 

def hello(name="World!"): print("Hello,", name) if __name__ == '__main__': hello("James!") Sunday, 11 August, 13 

Module(body=[ FunctionDef(name='hello', args=arguments(args=[arg(arg='name', annotation=None)], vararg=None, varargannotation=None, kwonlyargs=[], kwarg=None, kwargannotation=None, defaults=[Str(s='World!')], kw_defaults=[]), body=[ Expr(value=Call(func=Name(id='print', ctx=Load()), args=[Str(s='Hello,'), Name(id='name', ctx=Load())], keywords=[], starargs=None, kwargs=None))], decorator_list=[], returns=None), If(test=Compare(left=Name(id='__name__', ctx=Load()), ops=[Eq()], comparators=[Str(s='__main__')]), body=[ Expr(value=Call(func=Name(id='hello', ctx=Load()), args=[Str(s='James!')], keywords=[], starargs=None, kwargs=None))], orelse=[])]) Sunday, 11 August, 13 

http://goo.gl/iOVZt0 Sunday, 11 August, 13 

http://goo.gl/wyri9k Sunday, 11 August, 13 

1. an atom, or 2. an expression (x . y); where x and y are s- expressions Sunday, 11 August, 13 

Sunday, 11 August, 13 

TREES! Sunday, 11 August, 13 

(1 . (2 . (3 . nil))) Sunday, 11 August, 13 

(list 1 2 3) (defun square (a) (* a a)) Sunday, 11 August, 13 

eval/apply Sunday, 11 August, 13 

Getting Hy on Python Sunday, 11 August, 13 

Lexer Sunday, 11 August, 13 

def tokenize(buf): """ Tokenize a Lisp file or string buffer into internal Hy objects. """ try: return parser.parse(lexer.lex(buf)) except LexingError as e: pos = e.getsourcepos() raise LexException( "Could not identify the next token at line %s, column %s" % ( pos.lineno, pos.colno)) Sunday, 11 August, 13 

from rply import LexerGenerator lg = LexerGenerator() # A regexp for something that should end a quoting/unquoting operator # i.e. a space or a closing brace/paren/curly end_quote = r'(?![\s\)\]\}])' lg.add('LPAREN', r'\(') lg.add('RPAREN', r'\)') lg.add('LBRACKET', r'\[') lg.add('RBRACKET', r'\]') lg.add('LCURLY', r'\{') lg.add('RCURLY', r'\}') lg.add('QUOTE', r'\'%s' % end_quote) lg.add('QUASIQUOTE', r'`%s' % end_quote) lg.add('UNQUOTESPLICE', r'~@%s' % end_quote) lg.add('UNQUOTE', r'~%s' % end_quote) lg.add('HASHBANG', r'#!.*[^\r\n]') lg.add('STRING', r'''(?x) (?:u|r|ur|ru)? # prefix " # start string (?: | [^"\\] # non-quote or backslash | \\. # or escaped single character | \\x[0-9a-fA-F]{2} # or escaped raw character | \\u[0-9a-fA-F]{4} # or unicode escape | \\U[0-9a-fA-F]{8} # or long unicode escape )* # one or more times " # end string Sunday, 11 August, 13 

Parser Sunday, 11 August, 13 

pg = ParserGenerator( [rule.name for rule in lexer.rules] + ['$end'], cache_id="hy_parser" ) # ... @pg.production("paren : LPAREN list_contents RPAREN") @set_boundaries def paren(p): return HyExpression(p[1]) @pg.production("paren : LPAREN RPAREN") @set_boundaries def empty_paren(p): return HyExpression([]) Sunday, 11 August, 13 

Compiler Sunday, 11 August, 13 

In Case of Emergency • Lean forward • Place head firmly between knees • Scream until it goes away Sunday, 11 August, 13 

Problems Sunday, 11 August, 13 

def hy_eval(hytree, namespace, module_name): foo = HyObject() foo.start_line = 0 foo.end_line = 0 foo.start_column = 0 foo.end_column = 0 hytree.replace(foo) _ast, expr = hy_compile(hytree, module_name, get_expr=True) # Spoof the positions in the generated ast... for node in ast.walk(_ast): node.lineno = 1 node.col_offset = 1 for node in ast.walk(expr): node.lineno = 1 node.col_offset = 1 # Two-step eval: eval() the body of the exec call eval(ast_compile(_ast, "", "exec"), namespace) # Then eval the expression context and return that return eval(ast_compile(expr, "", "eval"), namespace) Sunday, 11 August, 13 

http://goo.gl/ce6jGN Sunday, 11 August, 13 

MACROS Sunday, 11 August, 13 

http://goo.gl/32eMO7 Sunday, 11 August, 13 

• Parameterize your boilerplate • DSLs • Cheat • Program your programs Sunday, 11 August, 13 

def macroexpand(tree, module_name): if isinstance(tree, HyExpression): if tree == []: return tree fn = tree[0] if fn in ("quote", "quasiquote"): return tree ntree = HyExpression(tree[:]) ntree.replace(tree) if isinstance(fn, HyString): m = _hy_macros[module_name].get(fn) if m is None: m = _hy_macros[None].get(fn) if m is not None: obj = _wrap_value(m(*ntree[1:])) obj.replace(tree) return obj return ntree return tree Sunday, 11 August, 13 

(defun princ [the-string] (kwapply (print the-string) {"end" ""})) (defn print-tag [name closingp &kwargs attrs] (princ "<") (if closingp (princ "/")) (princ (.lower name)) (if (and attrs (not closingp)) (do (princ " ") (princ (.join " " (list-comp (.format "{0}='{1}'" k v) [[k v] (.items attrs)]))))) (print ">")) ;; then at the repl... ;; => (print-tag "body" False {"padding" 20}) ;; ;; => (print-tag "body" True) ;; Sunday, 11 August, 13 

(defmacro tag [name attrs &rest body] (quasiquote (progn (kwapply (print-tag (unquote name) False) (unquote attrs)) (unquote-splice (list body)) (print-tag (unquote name) True)))) Sunday, 11 August, 13 

(tag "body" {"padding" 20} (tag "h1" {"color" "red"} (print "The Knutsens")) (tag "p" {} (print "Lorem ipsum dolor simet"))) ;; ;;

;; The Knutsens ;;

;;

;; Lorem ipsum dolor simet ;;

;; Sunday, 11 August, 13 

(defmacro html [&rest body] (quasiquote (tag "html" {} (do (unquote-splice (list body)))))) (defmacro body [attrs &rest body] (quasiquote (tag "body" (unquote attrs) (unquote-splice (list body))))) (defmacro h1 [attrs &rest body] (quasiquote (tag "h1" (unquote attrs) (unquote-splice (list body))))) (defmacro p [attrs &rest body] (quasiquote (tag "p" (unquote attrs) (unquote-splice (list body))))) Sunday, 11 August, 13 

(html (body {"padding" 20} (p {} (print "Who the f*ck are the Knutsen's!?")))) Sunday, 11 August, 13 

Sunday, 11 August, 13 

Join Us https://github.com/hylang/hy http://docs.hylang.org/en/latest/ Sunday, 11 August, 13 

Bonus Level Sunday, 11 August, 13 

Use ‘require’ to import modules with macros Sunday, 11 August, 13 

Interop is fun Sunday, 11 August, 13 

PDB works! Sunday, 11 August, 13