533 lines
4.6 KiB
HTML
533 lines
4.6 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of Option</TITLE>
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</HEAD><BODY>
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<H1>Option</H1>
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Section: OCaml library (3o)<BR>Updated: 2020-01-30<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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Option - Option values.
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<A NAME="lbAC"> </A>
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<H2>Module</H2>
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Module Option
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<A NAME="lbAD"> </A>
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<H2>Documentation</H2>
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<P>
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Module
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<B>Option</B>
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<BR> :
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<B>sig end</B>
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<P>
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<P>
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Option values.
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<P>
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Option values explicitly indicate the presence or absence of a value.
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<P>
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<P>
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<B>Since</B>
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4.08
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<P>
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<P>
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<P>
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<P>
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<P>
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<P>
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<P>
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<A NAME="lbAE"> </A>
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<H3>Options</H3>
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<P>
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<P>
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<I>type </I>
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<B>'a</B>
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<I>t </I>
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=
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<B>'a option</B>
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=
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<BR> | None
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<BR> | Some
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<B>of </B>
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<B>'a</B>
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<BR>
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<P>
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The type for option values. Either
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<B>None</B>
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or a value
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<B>Some v</B>
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.
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<P>
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<P>
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<P>
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<I>val none </I>
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:
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<B>'a option</B>
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<P>
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<P>
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<B>none</B>
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is
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<B>None</B>
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.
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<P>
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<P>
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<P>
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<I>val some </I>
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:
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<B>'a -> 'a option</B>
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<P>
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<P>
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<B>some v</B>
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is
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<B>Some v</B>
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.
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<P>
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<P>
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<P>
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<I>val value </I>
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:
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<B>'a option -> default:'a -> 'a</B>
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<P>
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<P>
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<B>value o ~default</B>
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is
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<B>v</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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and
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<B>default</B>
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otherwise.
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<P>
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<P>
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<P>
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<I>val get </I>
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:
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<B>'a option -> 'a</B>
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<P>
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<P>
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<B>get o</B>
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is
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<B>v</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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and
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<P>
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<P>
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<B>Raises Invalid_argument</B>
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otherwise.
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<P>
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<P>
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<P>
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<I>val bind </I>
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:
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<B>'a option -> ('a -> 'b option) -> 'b option</B>
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<P>
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<P>
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<B>bind o f</B>
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is
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<B>f v</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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and
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<B>None</B>
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if
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<B>o</B>
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is
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<B>None</B>
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.
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<P>
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<P>
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<P>
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<I>val join </I>
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:
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<B>'a option option -> 'a option</B>
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<P>
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<P>
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<B>join oo</B>
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is
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<B>Some v</B>
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if
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<B>oo</B>
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is
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<B>Some (Some v)</B>
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and
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<B>None</B>
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otherwise.
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<P>
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<P>
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<P>
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<I>val map </I>
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:
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<B>('a -> 'b) -> 'a option -> 'b option</B>
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<P>
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<P>
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<B>map f o</B>
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is
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<B>None</B>
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if
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<B>o</B>
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is
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<B>None</B>
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and
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<B>Some (f v)</B>
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is
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<B>o</B>
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is
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<B>Some v</B>
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.
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<P>
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<P>
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<P>
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<I>val fold </I>
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:
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<B>none:'a -> some:('b -> 'a) -> 'b option -> 'a</B>
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<P>
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<P>
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<B>fold ~none ~some o</B>
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is
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<B>none</B>
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if
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<B>o</B>
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is
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<B>None</B>
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and
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<B>some v</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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.
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<P>
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<P>
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<P>
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<I>val iter </I>
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:
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<B>('a -> unit) -> 'a option -> unit</B>
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<P>
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<P>
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<B>iter f o</B>
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is
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<B>f v</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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and
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<B>()</B>
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otherwise.
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<P>
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<P>
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<P>
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<P>
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<A NAME="lbAF"> </A>
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<H3>Predicates and comparisons</H3>
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<P>
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<P>
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<P>
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<I>val is_none </I>
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:
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<B>'a option -> bool</B>
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<P>
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<P>
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<B>is_none o</B>
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is
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<B>true</B>
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iff
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<B>o</B>
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is
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<B>None</B>
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.
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<P>
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<P>
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<P>
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<I>val is_some </I>
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:
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<B>'a option -> bool</B>
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<P>
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<P>
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<B>is_some o</B>
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is
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<B>true</B>
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iff
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<B>o</B>
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is
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<B>Some o</B>
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<P>
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<P>
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<P>
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<I>val equal </I>
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:
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<B>('a -> 'a -> bool) -> 'a option -> 'a option -> bool</B>
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<P>
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<P>
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<B>equal eq o0 o1</B>
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is
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<B>true</B>
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iff
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<B>o0</B>
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and
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<B>o1</B>
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are both
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<B>None</B>
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or if
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they are
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<B>Some v0</B>
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and
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<B>Some v1</B>
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and
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<B>eq v0 v1</B>
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is
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<B>true</B>
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.
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<P>
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<P>
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<P>
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<I>val compare </I>
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:
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<B>('a -> 'a -> int) -> 'a option -> 'a option -> int</B>
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<P>
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<P>
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<B>compare cmp o0 o1</B>
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is a total order on options using
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<B>cmp</B>
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to compare
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values wrapped by
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<B>Some _</B>
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.
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<B>None</B>
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is smaller than
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<B>Some _</B>
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values.
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<P>
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<P>
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<P>
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<P>
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<A NAME="lbAG"> </A>
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<H3>Converting</H3>
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<P>
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<P>
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<P>
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<I>val to_result </I>
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:
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<B>none:'e -> 'a option -> ('a, 'e) result</B>
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<P>
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<P>
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<B>to_result ~none o</B>
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is
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<B>Ok v</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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and
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<B>Error none</B>
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otherwise.
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<P>
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<P>
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<P>
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<I>val to_list </I>
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:
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<B>'a option -> 'a list</B>
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<P>
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<P>
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<B>to_list o</B>
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is
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<B>[]</B>
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if
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<B>o</B>
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is
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<B>None</B>
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and
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<B>[v]</B>
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if
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<B>o</B>
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is
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<B>Some v</B>
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<P>
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<P>
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<P>
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<I>val to_seq </I>
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:
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<B>'a option -> 'a Seq.t</B>
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<P>
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<P>
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<B>to_seq o</B>
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is
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<B>o</B>
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as a sequence.
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<B>None</B>
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is the empty sequence and
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<B>Some v</B>
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is the singleton sequence containing
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<B>v</B>
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.
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<P>
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<P>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">Module</A><DD>
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<DT id="3"><A HREF="#lbAD">Documentation</A><DD>
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<DL>
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<DT id="4"><A HREF="#lbAE">Options</A><DD>
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<DT id="5"><A HREF="#lbAF">Predicates and comparisons</A><DD>
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<DT id="6"><A HREF="#lbAG">Converting</A><DD>
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</DL>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:49 GMT, March 31, 2021
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</BODY>
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</HTML>
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