Month: February 2017

def fibo(n):
	in n <= 2:
		return 1
	else:
		return fibo(n-1)+fibo(n-2)

print fibo(20)
&#91;/python&#93;

&#91;python&#93;
chart = {}

def memofibo(n):
    if n in chart:
    	return chart&#91;n&#93;
    elif n <= 2:
    	chart&#91;n&#93; = 1
    
print memofibo(24)
&#91;/python&#93;

&#91;python&#93;
def t_javascript(token):
	r'<script\ type=\"text\/javascript\"\>'
	token.lexer.code_start = token.lexer.lexpos
	token.lexer.begin("javascript")

def t_javascript_end(token):

def t_javascript(token):
	r'<script\ type=\"text\/javascript\"\>'
	token.lexer.code_start = token.lexer.lexpos
	token.lexer.begin("javascript")

def t_javascript_end(token):
	r'\<\/script\>'
	token.value = token.lexer.lexdata[token.lexer.code_start:
		token.lexer.lexpos-9]
	token.type = 'JAVASCRIPT'
	token.lexer.lineno += token.value.count('\n')
	token.lexer.begin.('INITIAL')
	return token

parthing:構文解析 lexing:字句解析
after regular expression, lexer get token value.

#        function mymin(a, b){
#            if (a < b){
#                return a;
#            } else {
#                return b;
#            };
#        }
#        
#        function square(x){
#            return x * x;
#        }
#        
#        write(mymin(square(-2), square(3)));

def mymin(a, b):
	if (a < b):
		return a
	else:
		return b

def square(x):
	return x * x
print mymin(square(-2), square(3))

[1,2,3,4,5,6,7]

def odds_only(numbers):
	for N in numbers:
		if N % 2 == 1:
			yield N

def small_words(words):
	for word in words:
		if len(word) <= 3:
			yield word

print [w for w in small_words(["The","quick","brown","fox"])]

grammar = [
	("exp",["exp","+","exp"]),
	("exp",["exp","-","exp"]),
	("exp",["(","exp",")"]),
	("exp",["num"]),
]

def expand(tokens, grammar):
	for pos in range(len(tokens)):
		for rule in grammar:

depth = 1
utterances = [["exp"]]

def sublists(big_list, selected_so_far):
	if big_list == []:
		print selected_so_far
	else:
		current_element = big_list[0]
		rest_of_big_list = big_list[1:]
		sublists(rest_of_big_list, selected_so_far + [current_element])
		sublists(rest_of_big_list, selected_so_far )

	dinner_guests = ["LM", "ECS", "SBA"]
	sublists(dinner_guests, [])

def cfgempty(grammar, symbol, visited):
	if symbol in visited:
		return None
	elif not any([rule[0] == symbol for rule in grammar ]):
		return [symbol]
	else:
		new_visited = visited + [symbol]
		for rhs in [r[1] for r in grammar if r[0] == symbol]:
			if all([None] != cfgempty(frammar, r, new_visited) for r in rhs):
				result = []
				for r in rhs:
					result = result + cfgempty(grammar, r, new_visited)
				return result
		return None

tokens = (
	'IDENTIFIER',
	'NUMBER',
	'STRING'
	)

def t_NUMBER(t):
	r'-?[0-9]+(?:\.[0-9]*)?'
	t.value = float(t.value)
	return t

def t_STRING(t):
	r'([^"\\]|(\\.))*"'
	t.value = t.value[1:-1]
	return t

function gcd(a,b){
	if(a==b){
		return a;
	} else {
		if(a > b){
		return gcd(a-b, b);
		} else {
			return gcd(a, b- a)
		}
	}
}

recursion: function call itself

javascript and python

def uptoten(x):
if x < 10: return x else: return 10 javascriptcode=""" function uptoten(x) { if x < 10 { return x } else { return 10 } } """ [/python]

def findmax(f,l):
	best_element_sofar = None
	best_f_value_sofar = None
	for i in range(len(l)-1):
		elt = l[i]
		f_value = f(elt)
		if best_f_value_sofar == None or \
			f_value > best_f_value_sofar:
			best_element_sofar = elt
			best_f_value_sofar = f_value
	return best_element_sofar

Modern programming languages like Python can understand hexadecimal
numbers natively! Try it:

print 0x234 # uncomment me to see 564 printed
print 0xb # uncomment me to see 11 printed

import ply.lex as lex

tokens = ('NUM', 'ID')

def test_lexer(input_string):
	lexer.input(input_string)
	result = [ ]
	while True:
		tok = lexer.token()
		if not tok: break
		result = result + [(tok.type,tok.value)]
	return result

import re
re.findall(needle,haystack)

def t_LANGLESLASH(token):
    r'
def t_NUMBER(token):
	r"[0-9]+"
	token.value = int(token.value)
	return token

def t_STRING(token):
    r'"[^"]*"'
    return token

def t_WORD(token):
    r'[^ <>]+'
    return token

def t_IDENTIFIER(token):
    r'[a-zA-Z][a-zA-Z_]*'
    return token

def t_NUMBER(token):
    r'-?[0-9]+(:?\.[0-9]*)'   
    return token