49.sagews

#
# This is a header file for use by Math 190-001 at Emory University during fall semester 2008
#
# Math190 students: Press Shift-Return, then start doing things in the next box

# TextToNum("some text here") gives you a number as a Sage integer
import types
def TextToNum(txt):
    if type(txt) is not types.StringType:
        return 'ERROR'
    else:
        num = Integer(0);
        for i in range(len(txt)):
            num = 256*num + ord(txt[i])

        return(num)
            
# NumToText(some integer) gives back a string
def NumToText(num):
    tlist = Integer(num).digits(256)
    txt = ""
    for i in range(len(tlist)):
        txt = txt + chr(tlist[-i-1])

    return txt

# nextprime(15) gives the smallest prime bigger than 15, i.e., 17
def nextprime(num):
    return pari(num).nextprime()

# phi(n) tells you the Euler phi function of n
def phi(num):
    return euler_phi(num)

# compute the number x such that base^x = y mod n
def dlog(y, base, n):
    return sage.groups.generic.discrete_log(Mod(y, n), Mod(base, n))