A Taste of Boo

vegaseat 3 Tallied Votes 337 Views Share

Boo is new, well at least relatively new. If you are familiar with Python and C#, you can feel right at home. Most of Boo is written in C# by a Python devotee. Boo has static typing, but also mimics dynamic typing by inference. This way you are not in a complete straight-jacket. It runs in the NET or MONO environment, can be interpreted or compiled and a Python-like shell is available too. Boo is open source, developed enough to allow for serious experimentation. For those of you who have used the SharpDevelop IDE for C# there is a Boo plug-in. This code snippet will compile to a 10k executable file and can be distributed along with a 64k Boo.Lang.dll (runtime DLL) to other .NET or Mono computers. A utility to convert Boo to C#, or C# to Boo has been published.

ddanbe commented: Thanks for sharing! +14
# Just a taste of Boo ...
# Boo is a language that can be interpreted (with Booi.exe) or compiled
# (with Booc.exe), there is even a shell similar to the Python shell (Booish.exe).
# Boo works in the NET or MONO environment on Windows or Unix systems.
# You may notice the Python like syntax and some concepts borrowed from C#, Perl
# and Ruby.  It is easy to translate Python to Boo, but there are differences!
# Boo is open source and you can download it from: http://boo.codehaus.org/
# You do need the Microsoft NET or open source MONO environment on your machine.
# Most any programmer's editor will do, or download Booxw.exe from the above site.
# The Boo plugin for the SharpDevelop IDE works well too.
# tested with BOO_0.7.0       vegaseat      09nov2005

one line comments start with a Python # or a C //
you are looking at an example of a multiline comment

# any imports have to be done first ...
import System.IO  // for Directory

# next come all classes and functions ...
# (at least at this point in time)

# the indented lines are part of the function
# Boo uses the Python indented statement block
# the function's argument types have to be declared
# function return types can be inferred

def convertFahrenheit2Celsius(fahrenheit as double):
"""this would be the document string for the function"""
    celcius = 0.555 * (fahrenheit - 32)
    return celcius

# simple stuff first ...
print "Show a result the Python way ..."
print "Simple math like 12345679*63 =", 12345679*63

print "\n... or using Boo string interpolation ..."
print "Simple math like 12345679*63 = ${12345679*63}"

# print just an empty line

print "Display numbers 0 to 9 ..."
# the indentation makes the print statement part of the loop
for number in range(10):
    print number


print "Display numbers 0 to 9 on one line ..."
# print is a macro of System.Console.WriteLine() and adds a newline
# use System.Console.Write() to stay on the same line
# (using a comma to prevent the newline like in Python gives an error with Boo)

for number in range(10):
    //print number,
print; print

# just in case you think Boo has only for loops
# there is a while loop too
print "Count from 10 to 15, skip 13 ..."
k = 10
while k <= 15:
    unless k == 13:
        print k

# print 50 dashes
print "-"*50

# a little more complex this time
# Boo does have its roots in the C# language
# so we are using C# format specifiers in the output
# (the Python C-like format specifier % does not work!)
print "Square root of integers 0 to 9 formatted as a float with 4 decimals:"
for value in range(10):
    squareRoot = System.Math.Sqrt(value)
    System.Console.WriteLine("sqrt({0:D1}) = {1:F4}", value, squareRoot)


print "A not so typical for loop:"
for food in "spam", "eggs", "cumquats":
    print "I love", food


# strings can be enclosed in " or '
# (only " allows string interpolation)
animal = "hippopotamus"
print "this is the string    = ", animal
print "length of string      = ", len(animal)

# a short intro to string slicing
# a little cryptic at first blush, but very powerful
# [begin : < end]  note: end is exclusive
# defaults are begin = 0, end = length
# Python also has step, which is not implemented yet in Boo ...
print "exclude first 3 char  = ", animal[3: ]
print "exclude last 4 char   = ", animal[:-4]

print "reverse the string:"
for c in reversed(animal):
print; print

print "reverse first name and last name:"
name = "Ferdinand Porsche"
# Boo has built-in regex support, \s is space
firstname, lastname = @/\s/.Split(name)
print lastname, firstname

# or you can do it the no-regex way ...
firstname, lastname = name.Split()   # default is whitespace
print lastname, firstname


# Boo has lists similar to Python
list1 = List(range(8))
print list1.GetType()    # Boo.Lang.List
print list1              # [0, 1, 2, 3, 4, 5, 6, 7]
print "number of items in list       = ", len(list1)

# lists can be sliced too ...
print "exclude first 3 items in list = ", list1[3:]
print "first 3 items in list         = ", list1[:3]
print "exclude last 2 items in list  = ", list1[:-2]

# create a list of all items above value 3 ...
# (do behaves like a function)
list2 = list1.Collect() do (item as int):
    return item > 3
print "list1         = ", list1
print "all items > 3 = ", list2

# add to the list with Add or Push ...

# add another list ...
list1.Extend(["can", "be added", 3.1415])

print "added more items:", list1

# index is zero based
print "'any' is at index", list1.IndexOf('any')

# find 'can' ...
if 'can' in list1:
    print "'can' has been found"
# or ...
print "indeed 'can' has been found" if 'can' in list1

# use list comprehension ...
list3 = [k for k in list1 if k isa string]
print "just the string items: ", list3     # [any, type, can, be added]

# join the strings in list3 ...
str1 = list3.Join(" ")
print "join the strings: ", str1           # any type can be added   


# Boo has arrays that are similar to Python tuples
arr1 = array('ABCDE')
print arr1            # System.Object[]
print arr1.GetType()  # System.Object[]
print List(arr1)      # [A, B, C, D, E]
print arr1[1]         # B

if arr1[1] isa string:
    print arr1[1]
    print arr1[1].GetType()  # System.Char

for item in arr1:
    print item, cast(int, item)  # prints char and ASCII number eg.  A 65


print "Test boolean results ..."
print "Is 3 > 5? Result =", 3 > 5  # False, yes False and not false as documented
print "Is 3 < 5? Result =", 3 < 5  # True


Duck typing was coined by Dave Thomas in the Ruby community: 
"if it walks like a duck, and talks like a duck, then it is a duck".
This is a way to fake being a dynamic language like Python.
Useful, if you don't exactly know the type returned by an external call.

d as duck  // d accepts different types

d = 21     // sets d to an integer
print d
d += 12    // it can do everything an integer does
print d

d = "hypocrite"  // sets d to a string
print d
d = d.ToUpper()  // now it can do everything a string does
print d


# show files of a given extension from a given folder
ftype = "*.boo"
folder = "./"    // current folder
//folder = "D:/Boo/BooTest/"  // or specified folder

// print "Show string the Python way ..."
// print "All " + ftype + " files in folder " + folder + " :"

// ... or the Boo way ... 
print "All ${ftype} files in folder ${folder} :"

for fname in Directory.GetFiles(folder, ftype):
    print fname


# let's use the function we defined at the beginning
# (make sure you define/create the function before you call it)
print "A Fahrenheit to Celcius table:"
# range is from -40 to < 220 in steps of 10
for tf in range(-40, 220, 10):
    System.Console.WriteLine("{0:F1}F = {1:F1}C", tf, convertFahrenheit2Celsius(tf))


print "A more limited table:"
# another variation of the for loop ...
for tf in -40,0,32,98.6:
    System.Console.WriteLine("{0:F1}F = {1:F1}C", tf, convertFahrenheit2Celsius(tf))

prompt("Press enter to exit ...")  // optional console wait
vegaseat 1,735 DaniWeb's Hypocrite Team Colleague

Have to get the code field edited to accept Python syntax or the indentations are lost!!!!!

vegaseat 1,735 DaniWeb's Hypocrite Team Colleague

Actually Boo allows this more Python like construct:
print "{0:f1}F = {1:f1}C" % (tf, convertFahrenheit2Celsius(tf))

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