The Standard ML Basis Library

The ImperativeIO functor


functor ImperativeIO ( ... ) : IMPERATIVE_IO  (* OPTIONAL *)

The optional ImperativeIO functor can be used to implement (derive) an imperative-style stream I/O facility in terms of a lazy functional stream I/O facility. In the imperative style, input and output operations do not return a new stream each time but cause side-effects on their arguments. Most functions can raise the Io exception for various reasons, including illegal or inconsistent parameters, IO failures, and attempts to do I/O on closed output streams.

The ImperativeIO functor is not often needed, as the required BinIO and TextIO structures supply imperative-style I/O for most situations. It plays a useful role when the programmer needs to construct I/O facilities with element types other than char or Word8.word, or ones based on user-specified I/O primitives.

Functor argument interface

structure StreamIO : STREAM_IO
structure Vector : MONO_VECTOR
structure Array : MONO_ARRAY
sharing type StreamIO.elem = Vector.elem = Array.elem
sharing type StreamIO.vector = Vector.vector = Array.vector


structure StreamIO : STREAM_IO
The particular functional stream I/O facility from which this imperative I/O facility is derived. Most functions just call functions in StreamIO and do a little extra bookkeeping.

See Also


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Generated April 12, 2004
Last Modified April 15, 1996
Comments to John Reppy.

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