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Values
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<H2 CLASS="section"><A NAME="htoc53">6.2</A> Values</H2>
This section describes the kinds of values that are manipulated by
Objective Caml programs.<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc54">6.2.1</A> Base values</H3>
<H4 CLASS="subsubsection">Integer numbers</H4>
Integer values are integer numbers from −2<SUP>30</SUP> to 2<SUP>30</SUP>−1, that
is −1073741824 to 1073741823. The implementation may support a
wider range of integer values: on 64-bit platforms, the current
implementation supports integers ranging from −2<SUP>62</SUP> to 2<SUP>62</SUP>−1.<BR>
<BR>
<H4 CLASS="subsubsection">Floating-point numbers</H4>
Floating-point values are numbers in floating-point representation.
The current implementation uses double-precision floating-point
numbers conforming to the IEEE 754 standard, with 53 bits of mantissa
and an exponent ranging from −1022 to 1023.<BR>
<BR>
<H4 CLASS="subsubsection">Characters</H4>
Character values are represented as 8-bit integers between 0 and 255.
Character codes between 0 and 127 are interpreted following the ASCII
standard. The current implementation interprets character codes
between 128 and 255 following the ISO 8859-1 standard.<BR>
<BR>
<H4 CLASS="subsubsection">Character strings</H4> <A NAME="s:string-val"></A>
String values are finite sequences of characters. The current
implementation supports strings containing up to 2<SUP>24</SUP> − 5
characters (16777211 characters); on 64-bit platforms, the limit is
2<SUP>57</SUP> − 9.<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc55">6.2.2</A> Tuples</H3>
Tuples of values are written (<I>v</I><SUB>1</SUB>, …, <I>v<SUB>n</SUB></I>), standing for the
<I>n</I>-tuple of values <I>v</I><SUB>1</SUB> to <I>v<SUB>n</SUB></I>. The current implementation
supports tuple of up to 2<SUP>22</SUP> − 1 elements (4194303 elements).<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc56">6.2.3</A> Records</H3>
Record values are labeled tuples of values. The record value written
{ <I>field</I><SUB>1</SUB> = <I>v</I><SUB>1</SUB>; …; <I>field<SUB>n</SUB></I> = <I>v<SUB>n</SUB></I> } associates the value
<I>v<SUB>i</SUB></I> to the record field <I>field<SUB>i</SUB></I>, for <I>i</I> = 1 … <I>n</I>. The current
implementation supports records with up to 2<SUP>22</SUP> − 1 fields
(4194303 fields).<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc57">6.2.4</A> Arrays</H3>
Arrays are finite, variable-sized sequences of values of the same
type. The current implementation supports arrays containing up to
2<SUP>22</SUP> − 1 elements (4194303 elements)
<div style="background-color:yellow; color:red; border-style:none; border-width:0.5pt">
unless the elements are
floating-point numbers (2097151 elements in this case);
</div>
on 64-bit
platforms, the limit is 2<SUP>54</SUP> − 1 for all arrays.<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc58">6.2.5</A> Variant values</H3>
Variant values are either a constant constructor, or a pair of a
non-constant constructor and a value. The former case is written
<I>constr</I>; the latter case is written <I>constr</I>(<I>v</I>), where <I>v</I> is said
to be the argument of the non-constant constructor <I>constr</I>.<BR>
<BR>
The following constants are treated like built-in constant
constructors:
<BR>
<BR>
<DIV CLASS="center"><TABLE BORDER=1 CELLSPACING=0 CELLPADDING=1 WIDTH="80%">
<TR><TD ALIGN=center NOWRAP><B>Constant</B></TD>
<TD ALIGN=center NOWRAP><B>Constructor</B></TD>
</TR>
<TR><TD ALIGN=left NOWRAP>
<TT>false</TT></TD>
<TD ALIGN=left NOWRAP>the boolean false</TD>
</TR>
<TR><TD ALIGN=left NOWRAP><TT>true</TT></TD>
<TD ALIGN=left NOWRAP>the boolean true</TD>
</TR>
<TR><TD ALIGN=left NOWRAP><TT>()</TT></TD>
<TD ALIGN=left NOWRAP>the “unit” value</TD>
</TR>
<TR><TD ALIGN=left NOWRAP><TT>[]</TT></TD>
<TD ALIGN=left NOWRAP>the empty list</TD>
</TR></TABLE></DIV><BR>
<BR>
The current implementation limits each variant type to have at most
246 non-constant constructors.<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc59">6.2.6</A> Polymorphic variants</H3>
Polymorphic variants are an alternate form of variant values, not
belonging explicitly to a predefined variant type, and following
specific typing rules. They can be either constant, written
<TT><FONT COLOR=blue>`</FONT><FONT COLOR=maroon><I>tag-name</I></FONT></TT>, or non-constant, written <TT><FONT COLOR=blue>`</FONT><FONT COLOR=maroon><I>tag-name</I></FONT></TT> (<FONT COLOR=maroon><I><TT>v</TT></I></FONT>).<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc60">6.2.7</A> Functions</H3>
Functional values are mappings from values to values.<BR>
<BR>
<H3 CLASS="subsection"><A NAME="htoc61">6.2.8</A> Objects</H3>
Objects are composed of a hidden internal state which is a
record of instance variables, and a set of methods for accessing and
modifying these variables. The structure of an object is described by
the toplevel class that created it.<BR>
<BR>
<BR>
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