The expression
sequence [a,b,c,...]
is roughly equivalent to
do
r_a <- a
r_b <- b
r_c <- c
...
return [r_a,r_b,r_c,...]
The expression
sequence_ [a,b,c,...]
is roughly equivalent to
do
a
b
c
...
return ()
Does that help?
Cheers,
Greg
On 10/29/10 10:07 PM, Mark Spezzano wrote:
Hi,
Can somebody please explain exactly how the monad functions "sequence" and
"sequence_" are meant to work?
I have almost every Haskell textbook, but there's surprisingly little
information in them about the two functions.
From what I can gather, "sequence" and "sequence_" behave differently
depending on the types of the Monads that they are processing. Is this correct? Some concrete
examples would be really helpful.
Even references to some research papers that explain the rationale behind these
(and all the other..?) monad functions would be great.
Thanks in advance,
Mark Spezzano
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