concat(x, empty) is equal to x + ' ' + empty by definition of concat. If x = '' then x + ' ' + empty is equal to '' + ' ' + '' which is equal to ' ' so concat(x, empty) !== x
concat(x, empty)
x + ' ' + empty
concat
x = ''
'' + ' ' + ''
' '
concat(x, empty) !== x
Ah, yeah, I missed the extra space in the Semigroup instance
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concat(x, empty)
is equal tox + ' ' + empty
by definition ofconcat
. Ifx = ''
thenx + ' ' + empty
is equal to'' + ' ' + ''
which is equal to' '
soconcat(x, empty) !== x
Ah, yeah, I missed the extra space in the Semigroup instance