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maybe monad and friends

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maybe - return a tuple of (Nothing) or (Just,value)
maybemap - apply map function when maybe has a value and wrap in another maybe; else when nothing return nothing
maybevalue - return value of maybe; else when nothing return optional default args
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tpoindex 2019-09-11 22:47:39 -06:00
parent 9c238777e1
commit 912b3f2491
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29
test/maybe_test.sh Executable file
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#! /bin/bash
testMaybe() {
assertEquals '(Just,1)' "$(maybe 1)"
assertEquals '(Just,1)' "$(echo 1 | maybe)"
assertEquals '(Nothing)' "$(maybe '')"
assertEquals '(Nothing)' "$(maybe ' ')"
assertEquals '(Nothing)' "$(maybe ' ' ' ' ' ')"
assertEquals '(Nothing)' "$(echo | maybe)"
assertEquals '(Just,1 2 3)' "$(maybe 1 2 3)"
assertEquals '(Just,1 2 3)' "$(echo 1 2 3 | maybe)"
}
testMaybemap() {
assertEquals '(Just,3)' "$(echo 1 | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo $(( a + 1 ))')"
assertEquals '(Nothing)' "$(echo | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo $(( a + 1 ))')"
assertEquals '(Nothing)' "$(echo 1 | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo')"
assertEquals '(Nothing)' "$(echo 1 | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo' | maybemap lambda a . 'echo $(( a + 1 ))')"
}
testMaybevalue() {
assertEquals 3 "$(echo 1 | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo $(( a + 1 ))' | maybevalue 0)"
assertEquals 0 "$(echo | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo $(( a + 1 ))' | maybevalue 0)"
assertEquals 'a b c' "$(echo | maybe | maybemap lambda a . 'echo $(( a + 1 ))' | maybemap lambda a . 'echo $(( a + 1 ))' | maybevalue a b c)"
}
. ./shunit2-init.sh