abb and bab. Note that the substrings ca
Question 2. Find a regular expression that describes the given language:
(2.a) Language of strings over Σ = {a, b, c} in which every character c is followed by the character a.
(2.b) Language of strings over Σ = {a, b} which contain both substrings abb and bab. Note that the
substrings can occur in any order and can overlap, so for example the string babb is in this language.
(2.c) Let Σ = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, −, .}. The language L contains all strings that form a proper
decimal representation of some number.
Some examples of strings in the language: 42, -999, 0, 12.333, -0.14, 5.000.
Some examples of strings that are not in the language: 028 (leading zero), 75. (decimal point but no
decimal part), -.5 (no integer part), -0 (there is no negative zero), 4..2-6 (malformed nonsense).
You can use the shorthand [0−9] to stand for (0 + 1 + 2 + ···+ 9).
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