Different First Letter

Sometimes looking at the first character is enough to detect the inequality of two strings. If the first letters are different, the strings are not equal. The other characters in the strings do not matter.

Write this rule using a small letter x for the first letter of the first string, and a big letter X for the rest of the first string. The symbol + means concatenation. So the first string is x+X. (That is, the first string is its first character followed by the rest of its characters.)

Use a small letter y for the first letter of the secoond string, and a big letter Y for the rest of the second string. So the second string is y+Y. Now the rule is:

equals( x+X, y+Y ) = false if x != y

For example, equals( "mangrove", "acorn" ) is false. x is 'm' and X is "angrove". y is 'a' and Y is "corn".