refactor option double match to use combinators.#2

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osiire wants to merge 4 commits intokenichi-asai:masterfrom osiire:master

+17-26

Commits on Mar 4, 2015

refactor option double match to use combinators.
Satoshi Ogasawara
committed

Commits on Mar 5, 2015

remove needless 'rec'.
Satoshi Ogasawara
committed
remove a needless global flag.
Satoshi Ogasawara
committed
fix module dependency.
Satoshi Ogasawara
committed