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Adding Regular Expression koans.

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1 parent e1ada6c commit 9a459a7eb30ed6f676e4a6e7311b11b73bd16f56 @JEG2 committed Aug 21, 2010
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158 koans/about_regular_expressions.rb
@@ -0,0 +1,158 @@
+require File.expand_path(File.dirname(__FILE__) + '/edgecase')
+
+class AboutRegularExpressions < EdgeCase::Koan
+ def test_a_pattern_is_a_regular_expression
+ assert_equal Regexp, /pattern/.class
+ end
+
+ def test_a_regexp_can_search_a_string_for_matching_content
+ assert_equal "match", "some matching content"[/match/]
+ end
+
+ def test_a_failed_match_returns_nil
+ assert_equal __, "some matching content"[/missing/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_question_mark_means_optional
+ assert_equal __, "abbcccddddeeeee"[/ab?/]
+ assert_equal __, "abbcccddddeeeee"[/az?/]
+ end
+
+ def test_plus_means_one_or_more
+ assert_equal __, "abbcccddddeeeee"[/bc+/]
+ end
+
+ def test_asterisk_means_zero_or_more
+ assert_equal __, "abbcccddddeeeee"[/ab*/]
+ assert_equal __, "abbcccddddeeeee"[/az*/]
+ assert_equal __, "abbcccddddeeeee"[/z*/]
+
+ # THINK ABOUT IT:
+ #
+ # When would * fail to match?
+ end
+
+ # THINK ABOUT IT:
+ #
+ # We say that the repition operators above are "greedy."
+ #
+ # Why?
+
+ # ------------------------------------------------------------------
+
+ def test_the_left_most_match_wins
+ assert_equal __, "abbccc az"[/az*/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_character_classes_give_options_for_a_character
+ animals = ["cat", "bat", "rat", "zat"]
+ assert_equal __, animals.select { |a| a[/[cbr]at/] }
+ end
+
+ def test_slash_d_is_a_shortcut_for_a_digit_character_class
+ assert_equal __, "the number is 42"[/[0123456789]+/]
+ assert_equal __, "the number is 42"[/\d+/]
+ end
+
+ def test_character_classes_can_include_ranges
+ assert_equal __, "the number is 42"[/[0-9]+/]
+ end
+
+ def test_slash_s_is_a_shortcut_for_a_whitespace_character_class
+ assert_equal __, "space: \t\n"[/\s+/]
+ end
+
+ def test_slash_w_is_a_shortcut_for_a_word_character_class
+ # NOTE: This is more like how a programmer might define a word.
+ assert_equal __, "variable_1 = 42"[/[a-zA-Z0-9_]+/]
+ assert_equal __, "variable_1 = 42"[/\w+/]
+ end
+
+ def test_period_is_a_shortcut_for_any_non_newline_character
+ assert_equal __, "abc\n123"[/a.+/]
+ end
+
+ def test_a_character_class_can_be_negated
+ assert_equal __, "the number is 42"[/[^0-9]+/]
+ end
+
+ def test_shortcut_character_classes_are_negated_with_capitals
+ assert_equal __, "the number is 42"[/\D+/]
+ assert_equal __, "space: \t\n"[/\S+/]
+ assert_equal __, "variable_1 = 42"[/\W+/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_slash_a_anchors_to_the_start_of_the_string
+ assert_equal __, "start end"[/\Astart/]
+ assert_equal __, "start end"[/\Aend/]
+ end
+
+ def test_slash_z_anchors_to_the_end_of_the_string
+ assert_equal __, "start end"[/end\z/]
+ assert_equal __, "start end"[/start\z/]
+ end
+
+ def test_caret_anchors_to_the_start_of_lines
+ assert_equal __, "num 42\n2 lines"[/^\d+/]
+ end
+
+ def test_dollar_sign_anchors_to_the_end_of_lines
+ assert_equal __, "2 lines\nnum 42"[/\d+$/]
+ end
+
+ def test_slash_b_anchors_to_a_word_boundary
+ assert_equal __, "bovine vines"[/\bvine./]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_parentheses_group_contents
+ assert_equal __, "ahahaha"[/(ha)+/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_parentheses_also_capture_matched_content_by_number
+ assert_equal __, "Gray, James"[/(\w+), (\w+)/, 1]
+ assert_equal __, "Gray, James"[/(\w+), (\w+)/, 2]
+ end
+
+ def test_variables_can_also_be_used_to_access_captures
+ assert_equal __, "Name: Gray, James"[/(\w+), (\w+)/]
+ assert_equal __, $1
+ assert_equal __, $2
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_a_vertical_pipe_means_or
+ grays = /(James|Dana|Summer) Gray/
+ assert_equal __, "James Gray"[grays]
+ assert_equal __, "Summer Gray"[grays, 1]
+ assert_equal __, "Jim Gray"[grays, 1]
+ end
+
+ # THINK ABOUT IT:
+ #
+ # Explain the difference between a character class ([…]) and alternation (|).
+
+ # ------------------------------------------------------------------
+
+ def test_scan_is_like_find_all
+ assert_equal __, "one two-three".scan(/\w+/)
+ end
+
+ def test_sub_is_like_find_and_replace
+ assert_equal __, "one two-three".sub(/(t\w*)/) { $1[0, 1] }
+ end
+
+ def test_gsub_is_like_find_and_replace_all
+ assert_equal __, "one two-three".gsub(/(t\w*)/) { $1[0, 1] }
+ end
+end
View
4 koans/about_strings.rb
@@ -174,8 +174,8 @@ def test_strings_can_be_split_with_different_patterns
assert_equal [__, __, __, __], words
# NOTE: Patterns are formed from Regular Expressions. Ruby has a
- # very powerful Regular Expression library. Unfortunately, time
- # does not permit us to explore it in detail now.
+ # very powerful Regular Expression library. We will become
+ # enlightened about them soon.
end
def test_strings_can_be_joined
View
1 koans/path_to_enlightenment.rb
@@ -8,6 +8,7 @@
require 'about_array_assignment'
require 'about_hashes'
require 'about_strings'
+require 'about_regular_expressions'
require 'about_methods'
require 'about_constants'
require 'about_control_statements'
View
158 src/about_regular_expressions.rb
@@ -0,0 +1,158 @@
+require File.expand_path(File.dirname(__FILE__) + '/edgecase')
+
+class AboutRegularExpressions < EdgeCase::Koan
+ def test_a_pattern_is_a_regular_expression
+ assert_equal Regexp, /pattern/.class
+ end
+
+ def test_a_regexp_can_search_a_string_for_matching_content
+ assert_equal "match", "some matching content"[/match/]
+ end
+
+ def test_a_failed_match_returns_nil
+ assert_equal __(nil), "some matching content"[/missing/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_question_mark_means_optional
+ assert_equal __("ab"), "abbcccddddeeeee"[/ab?/]
+ assert_equal __("a"), "abbcccddddeeeee"[/az?/]
+ end
+
+ def test_plus_means_one_or_more
+ assert_equal __("bccc"), "abbcccddddeeeee"[/bc+/]
+ end
+
+ def test_asterisk_means_zero_or_more
+ assert_equal __("abb"), "abbcccddddeeeee"[/ab*/]
+ assert_equal __("a"), "abbcccddddeeeee"[/az*/]
+ assert_equal __(""), "abbcccddddeeeee"[/z*/]
+
+ # THINK ABOUT IT:
+ #
+ # When would * fail to match?
+ end
+
+ # THINK ABOUT IT:
+ #
+ # We say that the repition operators above are "greedy."
+ #
+ # Why?
+
+ # ------------------------------------------------------------------
+
+ def test_the_left_most_match_wins
+ assert_equal __("a"), "abbccc az"[/az*/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_character_classes_give_options_for_a_character
+ animals = ["cat", "bat", "rat", "zat"]
+ assert_equal __(["cat", "bat", "rat"]), animals.select { |a| a[/[cbr]at/] }
+ end
+
+ def test_slash_d_is_a_shortcut_for_a_digit_character_class
+ assert_equal __("42"), "the number is 42"[/[0123456789]+/]
+ assert_equal __("42"), "the number is 42"[/\d+/]
+ end
+
+ def test_character_classes_can_include_ranges
+ assert_equal __("42"), "the number is 42"[/[0-9]+/]
+ end
+
+ def test_slash_s_is_a_shortcut_for_a_whitespace_character_class
+ assert_equal __(" \t\n"), "space: \t\n"[/\s+/]
+ end
+
+ def test_slash_w_is_a_shortcut_for_a_word_character_class
+ # NOTE: This is more like how a programmer might define a word.
+ assert_equal __("variable_1"), "variable_1 = 42"[/[a-zA-Z0-9_]+/]
+ assert_equal __("variable_1"), "variable_1 = 42"[/\w+/]
+ end
+
+ def test_period_is_a_shortcut_for_any_non_newline_character
+ assert_equal __("abc"), "abc\n123"[/a.+/]
+ end
+
+ def test_a_character_class_can_be_negated
+ assert_equal __("the number is "), "the number is 42"[/[^0-9]+/]
+ end
+
+ def test_shortcut_character_classes_are_negated_with_capitals
+ assert_equal __("the number is "), "the number is 42"[/\D+/]
+ assert_equal __("space:"), "space: \t\n"[/\S+/]
+ assert_equal __(" = "), "variable_1 = 42"[/\W+/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_slash_a_anchors_to_the_start_of_the_string
+ assert_equal __("start"), "start end"[/\Astart/]
+ assert_equal __(nil), "start end"[/\Aend/]
+ end
+
+ def test_slash_z_anchors_to_the_end_of_the_string
+ assert_equal __("end"), "start end"[/end\z/]
+ assert_equal __(nil), "start end"[/start\z/]
+ end
+
+ def test_caret_anchors_to_the_start_of_lines
+ assert_equal __("2"), "num 42\n2 lines"[/^\d+/]
+ end
+
+ def test_dollar_sign_anchors_to_the_end_of_lines
+ assert_equal __("42"), "2 lines\nnum 42"[/\d+$/]
+ end
+
+ def test_slash_b_anchors_to_a_word_boundary
+ assert_equal __("vines"), "bovine vines"[/\bvine./]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_parentheses_group_contents
+ assert_equal __("hahaha"), "ahahaha"[/(ha)+/]
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_parentheses_also_capture_matched_content_by_number
+ assert_equal __("Gray"), "Gray, James"[/(\w+), (\w+)/, 1]
+ assert_equal __("James"), "Gray, James"[/(\w+), (\w+)/, 2]
+ end
+
+ def test_variables_can_also_be_used_to_access_captures
+ assert_equal __("Gray, James"), "Name: Gray, James"[/(\w+), (\w+)/]
+ assert_equal __("Gray"), $1
+ assert_equal __("James"), $2
+ end
+
+ # ------------------------------------------------------------------
+
+ def test_a_vertical_pipe_means_or
+ grays = /(James|Dana|Summer) Gray/
+ assert_equal __("James Gray"), "James Gray"[grays]
+ assert_equal __("Summer"), "Summer Gray"[grays, 1]
+ assert_equal __(nil), "Jim Gray"[grays, 1]
+ end
+
+ # THINK ABOUT IT:
+ #
+ # Explain the difference between a character class ([…]) and alternation (|).
+
+ # ------------------------------------------------------------------
+
+ def test_scan_is_like_find_all
+ assert_equal __(["one", "two", "three"]), "one two-three".scan(/\w+/)
+ end
+
+ def test_sub_is_like_find_and_replace
+ assert_equal __("one t-three"), "one two-three".sub(/(t\w*)/) { $1[0, 1] }
+ end
+
+ def test_gsub_is_like_find_and_replace_all
+ assert_equal __("one t-t"), "one two-three".gsub(/(t\w*)/) { $1[0, 1] }
+ end
+end
View
4 src/about_strings.rb
@@ -174,8 +174,8 @@ def test_strings_can_be_split_with_different_patterns
assert_equal [__("the"), __("rain"), __("in"), __("spain")], words
# NOTE: Patterns are formed from Regular Expressions. Ruby has a
- # very powerful Regular Expression library. Unfortunately, time
- # does not permit us to explore it in detail now.
+ # very powerful Regular Expression library. We will become
+ # enlightened about them soon.
end
def test_strings_can_be_joined
View
1 src/path_to_enlightenment.rb
@@ -8,6 +8,7 @@
require 'about_array_assignment'
require 'about_hashes'
require 'about_strings'
+require 'about_regular_expressions'
require 'about_methods'
require 'about_constants'
require 'about_control_statements'

1 comment on commit 9a459a7

@jpablobr

How cool! thanks!

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