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Basis.mkMonad
author Adam Chlipala <adam@chlipala.net>
date Fri, 19 Aug 2011 15:23:01 -0400
parents 6f046b4bad24
children 76dab73304a5
comparison
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1543:6f046b4bad24 1544:a99b743a3087
1380 \hspace{.1in} \to \mt{monad} \; \mt{m} \\ 1380 \hspace{.1in} \to \mt{monad} \; \mt{m} \\
1381 \hspace{.1in} \to \mt{t} \to \mt{m} \; \mt{t} \\ 1381 \hspace{.1in} \to \mt{t} \to \mt{m} \; \mt{t} \\
1382 \mt{val} \; \mt{bind} : \mt{m} ::: (\mt{Type} \to \mt{Type}) \to \mt{t1} ::: \mt{Type} \to \mt{t2} ::: \mt{Type} \\ 1382 \mt{val} \; \mt{bind} : \mt{m} ::: (\mt{Type} \to \mt{Type}) \to \mt{t1} ::: \mt{Type} \to \mt{t2} ::: \mt{Type} \\
1383 \hspace{.1in} \to \mt{monad} \; \mt{m} \\ 1383 \hspace{.1in} \to \mt{monad} \; \mt{m} \\
1384 \hspace{.1in} \to \mt{m} \; \mt{t1} \to (\mt{t1} \to \mt{m} \; \mt{t2}) \\ 1384 \hspace{.1in} \to \mt{m} \; \mt{t1} \to (\mt{t1} \to \mt{m} \; \mt{t2}) \\
1385 \hspace{.1in} \to \mt{m} \; \mt{t2} 1385 \hspace{.1in} \to \mt{m} \; \mt{t2} \\
1386 \mt{val} \; \mt{mkMonad} : \mt{m} ::: (\mt{Type} \to \mt{Type}) \\
1387 \hspace{.1in} \to \{\mt{Return} : \mt{t} ::: \mt{Type} \to \mt{t} \to \mt{m} \; \mt{t}, \\
1388 \hspace{.3in} \mt{Bind} : \mt{t1} ::: \mt{Type} \to \mt{t2} ::: \mt{Type} \to \mt{m} \; \mt{t1} \to (\mt{t1} \to \mt{m} \; \mt{t2}) \to \mt{m} \; \mt{t2}\} \\
1389 \hspace{.1in} \to \mt{monad} \; \mt{m}
1386 \end{array}$$ 1390 \end{array}$$
1387 1391
1388 \subsection{Transactions} 1392 \subsection{Transactions}
1389 1393
1390 Ur is a pure language; we use Haskell's trick to support controlled side effects. The standard library defines a monad $\mt{transaction}$, meant to stand for actions that may be undone cleanly. By design, no other kinds of actions are supported. 1394 Ur is a pure language; we use Haskell's trick to support controlled side effects. The standard library defines a monad $\mt{transaction}$, meant to stand for actions that may be undone cleanly. By design, no other kinds of actions are supported.