2020-01-07

filter.py

# Implement array.filter() by hand (or whatever your language of choice uses to do this functionality).

def filter(array, filterFunction):
    newArray = []
    for item in array:
        isFilterTrue, updatedItem = filterFunction(item)
        if isFilterTrue:
            if updatedItem:
                newArray.append(updatedItem)
            else:
                newArray.append(item)
    return newArray

def longerThan6(item):
    if len(str(item)) > 6:
        return True, item
    else:
        return False, item

print("using Array.prototype.filter() web page for examples")

def over10(item):
    if item >= 10:
        return True, item
    else:
        return False, item

print("")
print("filter on values >= 10")
a = [12, 5, 8, 130, 44]
print("input: ", a)
b = filter(a, over10)
print("output: ",b)

print("")
print("filter on strings > 6 characters")
c = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present']
print("input: ", c)
d = filter(c, longerThan6)
print("output: ",d)

def apFilter(item):
    if item.lower().find('ap') != -1:
        return True, item
    else:
        return False, item

print("")
print("Filter on 'ap'")
e = ['apple', 'banana', 'grapes', 'mango', 'orange']
print("input:", e)
f = filter(e, apFilter)
print("output: ",f)

def doubleValue(item):
    doubledItem = 2 * item
    return True, doubledItem

print("")
print("Double each input value")
h = [ 1, 2, 3, 4]
print("input: ", h)
j = filter(h, doubleValue)
print("output:" ,j)

print("")
print("Append 'foo' to each word")
def appendFoo(item):
    appendedItem = item + "Foo"
    return True, appendedItem

print("input: ", e)
k = filter(e, appendFoo)
print("output: ", k)

print("")
print("Demonstrate nested filters: triple each input, then test for being odd")
def tripleValue(item):
    tripledItem = 3 * item
    return True, tripledItem

def isOdd(item):
    if (item % 2) == 1:
        return True, item
    else:
        return False, item

print("input: ", h)
l = filter(filter(h, tripleValue), isOdd)
print("output:", l)

m = [
    { "key": "one",   "value": 1},
    { "key": "two",   "value": 2},
    { "key": "three", "value": 3},
    { "key": "four",  "value": 4},
    { "key": "five",  "value": 5}
]

def dictValueIsOdd(item):
    if (item["value"] % 2) == 1:
        return True, item
    else:
        return False, item

print("")
print("Filter based on value within dictionary")

print("input:", m)
n = filter(m, dictValueIsOdd)
print("output: ", n)