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# Soros Tutorial Two 🍒 Fruitful Expressions
#
# We learn the basics of regular expressions,
# writing a program to convert even input
# numbers to apples, and odd numbers to pears.
#
# INTRODUCTION
#
# Regular expression (regexp or regex or RE) is
# a standard for pattern matching and replacement,
# supported by every modern programming languages.
#
# Why? Because it’s the easiest way to handle
# input texts.
#
# A Soros program line can be a regular
# expression pattern and replacement:
#
# regex_pattern regex replacement
# TASK 1
#
# The character . (dot) matches arbitrary
# characters in a regex pattern.
#
# Remove the # in the following program to add
# bananas to all 1-digit numbers (except one),
# and tangerines to all 2-digit numbers, and extend
# the third program line to convert all 3-digit
# numbers to pineapples (scroll the output
# window to the end to see 3-digit numbers)!
1 one
#. 🍌 (1-DIGIT)
#.. 🍊 (2-DIGIT)
🍍
# NOTE: Solutions are there in the end of this tutorial.
# TASK 2
#
# Dots can be combined with arbitrary other
# characters.
#
# Extend the previous program with a single
# program line to replace 10, 20, 30 ... 90
# with lemons instead of bananas!
# (Copy this lemon emoji: 🍋).
#
# TASK 3
#
# We can limit the previous pattern only for
# given characters, putting them between brackets.
#
# For example, [abcd] matches only the letter a, b, c and d.
#
# Add a *single* program line to the previous program to
# to replace every 2-digit *even* number with an apple, ie.
# compressing the following 45-line long program:
#
# 10 🍎 (EVEN)
# 12 🍎 (EVEN)
# ...
# 98 🍎 (EVEN)
# TASK 4
#
# The .+ (dot plus) matches 1 or more arbitrary characters.
#
# What will be the effect of the following program line, if
# you change the first line “1 one” with it, and remove the
# sign of comment? Guess it, and check it!
#.+ 🍎🍎🍎
# TASK 5
#
# We can combine the different regex patterns, for example, the
# dot plus pattern with the bracket one.
#
# Write a program from scratch (removing the old program lines)
# to show apples and pears for every 2-digit or more input
# number, using .+ and bracket expressions!
#
# 10 🍎 (EVEN)
# 11 🍐 (ODD)
# 12 🍎 (EVEN)
# ...
# 100 🍎 (EVEN)
# 101 🍐 (ODD)
# etc.
# TASK 6
#
# The .* (dot asterisk) matches 0 or more arbitrary characters.
#
# Replace the first program line “1 one” with a program line to
# convert all even input numbers (including the 1-letter ones)
# to apples, and insert a new program line to convert all
# odd numbers to pears.
SCROLL DOWN FOR SOLUTIONS
⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩⇩
# SOLUTION – TASK 1
#
# 1 one
# . 🍌 (1-DIGIT)
# .. 🍊 (2-DIGIT)
# ... 🍍 (3-DIGIT)
# SOLUTION – TASK 2
#
# 1 one
# . 🍌 (1-DIGIT)
# .0 🍋 (10×n)
# .. 🍊 (2-DIGIT)
# ... 🍍 (3-DIGIT)
# SOLUTION – TASK 3
#
# 1 one
# . 🍌 (1-DIGIT)
# .[02468] 🍎 (EVEN 2-DIGIT)
# .0 🍋 (10×n)
# .. 🍊 (2-DIGIT)
# ... 🍍 (3-DIGIT)
# SOLUTION – TASK 4
#
# All numbers converted to "🍎🍎🍎", because .+ matches
# every input text, so the following program lines
# will never be executed, so we can remove them:
#
# .+ 🍎🍎🍎
# SOLUTION – TASK 5
#
# 2-digit or bigger numbers are converted to
# apples and pears by the following two lines:
#
# .+[02468] 🍎 (EVEN 2-OR-MORE-DIGIT)
# .+[13579] 🍐 (ODD 2-OR-MORE-DIGIT)
#
# or simply
#
# .+[02468] 🍎 (EVEN 2-OR-MORE-DIGIT)
# .+. 🍐 (ODD 2-OR-MORE-DIGIT)
# SOLUTION – TASK 6
#
# Change + with * in the previous program to convert
# every (1-digit or larger) number to apples and pears:
#
# .*[02468] 🍎 (EVEN NUMBER)
# .* 🍐 (ODD NUMBER)
######################################################
# CONGRATULATIONS – You have finished Tutorial Two! 🙂
######################################################
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