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<h2 id="head-dde02609261bd0c16866b9a827640d68bbe6a821">Ix - Library Documentation</h2>
<p>
Part of the <a href="/hawiki/LibraryDocumentation">LibraryDocumentation</a> project.
</p>
<p>
Controls indexing, typically used in conjunction with <a class="nonexistent" href="/hawiki/LibraryDocumentation_2fArray">?</a>LibraryDocumentation/Array.
</p>
<pre class=code>
<B><FONT COLOR="#A020F0">module</FONT></B> Ix ( Ix(range, index, inRange), rangeSize ) <B><FONT COLOR="#A020F0">where</FONT></B>
<B><FONT COLOR="#A020F0">class</FONT></B> (Ord a) => Ix a <B><FONT COLOR="#A020F0">where</FONT></B>
range <FONT COLOR="#228B22"><B>:: (a,a) -> [a]
</FONT></B> index <FONT COLOR="#228B22"><B>:: (a,a) -> a -> Int
</FONT></B> inRange <FONT COLOR="#228B22"><B>:: (a,a) -> a -> Bool
</FONT></B>
rangeSize <FONT COLOR="#228B22"><B>:: Ix a => (a,a) -> Int
</FONT></B>rangeSize b@(l,h) | null (range b) = 0
| otherwise = index b h + 1
<I><FONT COLOR="#B22222">-- NB: replacing "null (range b)" by "l > h" fails if
</FONT></I><I><FONT COLOR="#B22222">-- the bounds are tuples. For example,
</FONT></I><I><FONT COLOR="#B22222">-- (2,1) > (1,2),
</FONT></I><I><FONT COLOR="#B22222">-- but
</FONT></I><I><FONT COLOR="#B22222">-- range ((2,1),(1,2)) = []
</FONT></I>
<B><FONT COLOR="#A020F0">instance</FONT></B> Ix Char <B><FONT COLOR="#A020F0">where</FONT></B>
range (m,n) = [m..n]
index b@(c,c') ci
| inRange b ci = fromEnum ci - fromEnum c
| otherwise = error <FONT COLOR="#BC8F8F"><B>"Ix.index: Index out of range."</FONT></B>
inRange (c,c') i = c <= i && i <= c'
<B><FONT COLOR="#A020F0">instance</FONT></B> Ix Int <B><FONT COLOR="#A020F0">where</FONT></B>
range (m,n) = [m..n]
index b@(m,n) i
| inRange b i = i - m
| otherwise = error <FONT COLOR="#BC8F8F"><B>"Ix.index: Index out of range."</FONT></B>
inRange (m,n) i = m <= i && i <= n
<B><FONT COLOR="#A020F0">instance</FONT></B> Ix Integer <B><FONT COLOR="#A020F0">where</FONT></B>
range (m,n) = [m..n]
index b@(m,n) i
| inRange b i = fromInteger (i - m)
| otherwise = error <FONT COLOR="#BC8F8F"><B>"Ix.index: Index out of range."</FONT></B>
inRange (m,n) i = m <= i && i <= n
<B><FONT COLOR="#A020F0">instance</FONT></B> (Ix a,Ix b) => Ix (a, b) <I><FONT COLOR="#B22222">-- as derived, for all tuples
</FONT></I><B><FONT COLOR="#A020F0">instance</FONT></B> Ix Bool <I><FONT COLOR="#B22222">-- as derived
</FONT></I><B><FONT COLOR="#A020F0">instance</FONT></B> Ix Ordering <I><FONT COLOR="#B22222">-- as derived
</FONT></I><B><FONT COLOR="#A020F0">instance</FONT></B> Ix () <I><FONT COLOR="#B22222">-- as derived
</FONT></I></PRE>
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<p>
<a id="v:index"> <h3 id="head-8b66ce514e1ab53baa1ebe66a4af6f1888633181">index :: Ix a => (a,a) -> a -> Int</h3>
</p>
<p>
maps a bounding pair, which defines the lower and upper bounds of the range, and a subscript, to an integer.
</p>
<pre class=code>
> index (10,15) 12
2
> index (<FONT COLOR="#BC8F8F"><B>'A'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'Z'</FONT></B>) <FONT COLOR="#BC8F8F"><B>'Z'</FONT></B>
25
> index ((1,5),(6,10)) (3,7)
14
</PRE>
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</p>
<p>
<a id="v:inRange"> <h3 id="head-c08754f3aacece95e4cb9c733d7ea17c99235b51">inRange :: Ix a => (a,a) -> a -> Bool</h3>
</p>
<p>
Returns True if a particular subscript lies in the range defined by a bounding pair.
</p>
<pre class=code>
> inRange (1,5) 3
True
> inRange (1,5) 12
False
> inRange ((1,5),(10,12)) (7,8)
True
</PRE>
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<p>
<a id="v:range"> <h3 id="head-fc36039f6140a31c1b23060b6947b7365e915d7f">range :: Ix a => (a,a) -> [a]</h3>
</p>
<p>
The range operation enumerates all subscripts.
</p>
<pre class=code>
> range (3,6)
[3,4,5,6]
> range ((1,3),(2,4))
[(1,3),(1,4),(2,3),(2,4)]
> range (<FONT COLOR="#BC8F8F"><B>'e'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'i'</FONT></B>)
<FONT COLOR="#BC8F8F"><B>"efghi"</FONT></B>
> range ((<FONT COLOR="#BC8F8F"><B>'a'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'d'</FONT></B>))
[(<FONT COLOR="#BC8F8F"><B>'a'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'a'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'a'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'d'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'d'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'b'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>),(<FONT COLOR="#BC8F8F"><B>'c'</FONT></B>,<FONT COLOR="#BC8F8F"><B>'d'</FONT></B>)]
</PRE>
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<p>
<a id="v:rangeSize"> <h3 id="head-b0badd06df078ffb18abba0f50563ee6e112c4ee">rangeSize :: Ix a => (a,a) -> Int</h3>
</p>
<p>
TODO
</p>
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