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<title>src/Text/ParserCombinators/Poly/StateParser.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>-- | This module contains the definitions for a generic parser, with</span>
<a name="line-2"></a><span class='hs-comment'>-- running state. These are the parts that are shared between the State</span>
<a name="line-3"></a><span class='hs-comment'>-- and StateLazy variations. Do not import this module directly, but only</span>
<a name="line-4"></a><span class='hs-comment'>-- via T.P.Poly.State or T.P.Poly.StateLazy.</span>
<a name="line-5"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Text</span><span class='hs-varop'>.</span><span class='hs-conid'>ParserCombinators</span><span class='hs-varop'>.</span><span class='hs-conid'>Poly</span><span class='hs-varop'>.</span><span class='hs-conid'>StateParser</span>
<a name="line-6"></a> <span class='hs-layout'>(</span> <span class='hs-comment'>-- * The Parser datatype</span>
<a name="line-7"></a> <span class='hs-conid'>Parser</span><span class='hs-layout'>(</span><span class='hs-conid'>P</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- datatype, instance of: Functor, Monad, PolyParse</span>
<a name="line-8"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>Result</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- internal to the parser monad</span>
<a name="line-9"></a> <span class='hs-comment'>-- ** basic parsers</span>
<a name="line-10"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>next</span> <span class='hs-comment'>-- :: Parser s t t</span>
<a name="line-11"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>eof</span> <span class='hs-comment'>-- :: Parser s t ()</span>
<a name="line-12"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>satisfy</span> <span class='hs-comment'>-- :: (t->Bool) -> Parser s t t</span>
<a name="line-13"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>onFail</span> <span class='hs-comment'>-- :: Parser s t a -> Parser s t a -> Parser s t a</span>
<a name="line-14"></a> <span class='hs-comment'>-- ** State-handling</span>
<a name="line-15"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>stUpdate</span> <span class='hs-comment'>-- :: (s->s) -> Parser s t ()</span>
<a name="line-16"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>stQuery</span> <span class='hs-comment'>-- :: (s->a) -> Parser s t a</span>
<a name="line-17"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>stGet</span> <span class='hs-comment'>-- :: Parser s t s</span>
<a name="line-18"></a> <span class='hs-comment'>-- ** re-parsing</span>
<a name="line-19"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>reparse</span> <span class='hs-comment'>-- :: [t] -> Parser s t ()</span>
<a name="line-20"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-21"></a>
<a name="line-22"></a>
<a name="line-23"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Text</span><span class='hs-varop'>.</span><span class='hs-conid'>ParserCombinators</span><span class='hs-varop'>.</span><span class='hs-conid'>Poly</span><span class='hs-varop'>.</span><span class='hs-conid'>Base</span>
<a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Text</span><span class='hs-varop'>.</span><span class='hs-conid'>ParserCombinators</span><span class='hs-varop'>.</span><span class='hs-conid'>Poly</span><span class='hs-varop'>.</span><span class='hs-conid'>Result</span>
<a name="line-25"></a>
<a name="line-26"></a><a name="Parser"></a><span class='hs-comment'>-- | This @Parser@ datatype is a fairly generic parsing monad with error</span>
<a name="line-27"></a><a name="Parser"></a><span class='hs-comment'>-- reporting, and running state.</span>
<a name="line-28"></a><a name="Parser"></a><span class='hs-comment'>-- It can be used for arbitrary token types, not just String input.</span>
<a name="line-29"></a><a name="Parser"></a><span class='hs-comment'>-- (If you do not require a running state, use module Poly.Plain instead)</span>
<a name="line-30"></a><a name="Parser"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>t</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Result</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>[</span><span class='hs-varid'>t</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-31"></a>
<a name="line-32"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Functor</span> <span class='hs-layout'>(</span><span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-33"></a> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span><span class='hs-keyglyph'>-></span> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>p</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-34"></a>
<a name="line-35"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-layout'>(</span><span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-36"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-37"></a> <span class='hs-varid'>fail</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Failure</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-38"></a> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varop'>>>=</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span><span class='hs-keyglyph'>-></span> <span class='hs-varid'>continue</span> <span class='hs-varop'>.</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-39"></a> <span class='hs-keyword'>where</span>
<a name="line-40"></a> <span class='hs-varid'>continue</span> <span class='hs-layout'>(</span><span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>g'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>g</span> <span class='hs-varid'>x</span> <span class='hs-keyword'>in</span> <span class='hs-varid'>g'</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span>
<a name="line-41"></a> <span class='hs-varid'>continue</span> <span class='hs-layout'>(</span><span class='hs-conid'>Committed</span> <span class='hs-layout'>(</span><span class='hs-conid'>Committed</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>continue</span> <span class='hs-layout'>(</span><span class='hs-conid'>Committed</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-42"></a> <span class='hs-varid'>continue</span> <span class='hs-layout'>(</span><span class='hs-conid'>Committed</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Committed</span> <span class='hs-layout'>(</span><span class='hs-varid'>continue</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-43"></a> <span class='hs-varid'>continue</span> <span class='hs-layout'>(</span><span class='hs-conid'>Failure</span> <span class='hs-varid'>tss</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Failure</span> <span class='hs-varid'>tss</span> <span class='hs-varid'>e</span>
<a name="line-44"></a>
<a name="line-45"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Commitment</span> <span class='hs-layout'>(</span><span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-46"></a> <span class='hs-varid'>commit</span> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Committed</span> <span class='hs-varop'>.</span> <span class='hs-varid'>p</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-47"></a> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-varop'>`adjustErr`</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span><span class='hs-keyglyph'>-></span> <span class='hs-varid'>adjust</span> <span class='hs-varop'>.</span> <span class='hs-varid'>p</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-48"></a> <span class='hs-keyword'>where</span>
<a name="line-49"></a> <span class='hs-varid'>adjust</span> <span class='hs-layout'>(</span><span class='hs-conid'>Failure</span> <span class='hs-varid'>zs</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Failure</span> <span class='hs-varid'>zs</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-50"></a> <span class='hs-varid'>adjust</span> <span class='hs-layout'>(</span><span class='hs-conid'>Committed</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Committed</span> <span class='hs-layout'>(</span><span class='hs-varid'>adjust</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-51"></a> <span class='hs-varid'>adjust</span> <span class='hs-varid'>good</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>good</span>
<a name="line-52"></a>
<a name="line-53"></a> <span class='hs-varid'>oneOf'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>accum</span> <span class='hs-conid'>[]</span>
<a name="line-54"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>accum</span> <span class='hs-varid'>errs</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span>
<a name="line-55"></a> <span class='hs-varid'>fail</span> <span class='hs-layout'>(</span><span class='hs-str'>"failed to parse any of the possible choices:\n"</span>
<a name="line-56"></a> <span class='hs-varop'>++</span><span class='hs-varid'>indent</span> <span class='hs-num'>2</span> <span class='hs-layout'>(</span><span class='hs-varid'>concatMap</span> <span class='hs-varid'>showErr</span> <span class='hs-layout'>(</span><span class='hs-varid'>reverse</span> <span class='hs-varid'>errs</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-57"></a> <span class='hs-varid'>accum</span> <span class='hs-varid'>errs</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>e</span><span class='hs-layout'>,</span><span class='hs-conid'>P</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>ps</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-58"></a> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>p</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span> <span class='hs-keyword'>of</span>
<a name="line-59"></a> <span class='hs-conid'>Failure</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>err</span> <span class='hs-keyglyph'>-></span>
<a name="line-60"></a> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>accum</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>e</span><span class='hs-layout'>,</span><span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>errs</span><span class='hs-layout'>)</span> <span class='hs-varid'>ps</span>
<a name="line-61"></a> <span class='hs-keyword'>in</span> <span class='hs-varid'>p</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span>
<a name="line-62"></a> <span class='hs-varid'>r</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Success</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>r</span>
<a name="line-63"></a> <span class='hs-varid'>r</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Committed</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>r</span> <span class='hs-layout'>)</span>
<a name="line-64"></a> <span class='hs-varid'>showErr</span> <span class='hs-layout'>(</span><span class='hs-varid'>name</span><span class='hs-layout'>,</span><span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>name</span><span class='hs-varop'>++</span><span class='hs-str'>":\n"</span><span class='hs-varop'>++</span><span class='hs-varid'>indent</span> <span class='hs-num'>2</span> <span class='hs-varid'>err</span>
<a name="line-65"></a>
<a name="line-66"></a><span class='hs-keyword'>infixl</span> <span class='hs-num'>6</span> <span class='hs-varop'>`onFail`</span> <span class='hs-comment'>-- not sure about precedence 6?</span>
<a name="line-67"></a>
<a name="line-68"></a><a name="onFail"></a><span class='hs-comment'>-- | @p `onFail` q@ means parse p, unless p fails, in which case</span>
<a name="line-69"></a><span class='hs-comment'>-- parse q instead.</span>
<a name="line-70"></a><span class='hs-comment'>-- Can be chained together to give multiple attempts to parse something.</span>
<a name="line-71"></a><span class='hs-comment'>-- (Note that q could itself be a failing parser, e.g. to change the error</span>
<a name="line-72"></a><span class='hs-comment'>-- message from that defined in p to something different.)</span>
<a name="line-73"></a><span class='hs-comment'>-- However, a severe failure in p cannot be ignored.</span>
<a name="line-74"></a><span class='hs-definition'>onFail</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>a</span>
<a name="line-75"></a><a name="onFail"></a><span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-varop'>`onFail`</span> <span class='hs-layout'>(</span><span class='hs-conid'>P</span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-varid'>continue</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span> <span class='hs-varop'>$</span> <span class='hs-varid'>p</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-layout'>)</span>
<a name="line-76"></a> <span class='hs-keyword'>where</span>
<a name="line-77"></a> <span class='hs-varid'>continue</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span> <span class='hs-layout'>(</span><span class='hs-conid'>Failure</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>q</span> <span class='hs-varid'>s</span> <span class='hs-varid'>ts</span>
<a name="line-78"></a> <span class='hs-comment'>-- continue _ _ (Committed r) = r -- no, remain Committed</span>
<a name="line-79"></a> <span class='hs-varid'>continue</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>r</span>
<a name="line-80"></a>
<a name="line-81"></a><span class='hs-comment'>------------------------------------------------------------------------</span>
<a name="line-82"></a>
<a name="line-83"></a><a name="next"></a><span class='hs-comment'>-- | Simply return the next token in the input tokenstream.</span>
<a name="line-84"></a><span class='hs-definition'>next</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>t</span>
<a name="line-85"></a><span class='hs-definition'>next</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ts</span> <span class='hs-keyword'>of</span>
<a name="line-86"></a> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Failure</span> <span class='hs-layout'>(</span><span class='hs-conid'>[]</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-str'>"Ran out of input (EOF)"</span>
<a name="line-87"></a> <span class='hs-layout'>(</span><span class='hs-varid'>t</span><span class='hs-conop'>:</span><span class='hs-varid'>ts'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts'</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varid'>t</span> <span class='hs-layout'>)</span>
<a name="line-88"></a>
<a name="line-89"></a><a name="eof"></a><span class='hs-comment'>-- | Succeed if the end of file/input has been reached, fail otherwise.</span>
<a name="line-90"></a><span class='hs-definition'>eof</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-conid'>()</span>
<a name="line-91"></a><span class='hs-definition'>eof</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ts</span> <span class='hs-keyword'>of</span>
<a name="line-92"></a> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-conid'>[]</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-conid'>()</span>
<a name="line-93"></a> <span class='hs-layout'>(</span><span class='hs-varid'>t</span><span class='hs-conop'>:</span><span class='hs-varid'>ts'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Failure</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-str'>"Expected end of input (eof)"</span> <span class='hs-layout'>)</span>
<a name="line-94"></a>
<a name="line-95"></a>
<a name="line-96"></a><a name="satisfy"></a><span class='hs-comment'>-- | Return the next token if it satisfies the given predicate.</span>
<a name="line-97"></a><span class='hs-definition'>satisfy</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-varid'>t</span><span class='hs-keyglyph'>-></span><span class='hs-conid'>Bool</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>t</span>
<a name="line-98"></a><span class='hs-definition'>satisfy</span> <span class='hs-varid'>pred</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <span class='hs-layout'>{</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>next</span>
<a name="line-99"></a> <span class='hs-layout'>;</span> <span class='hs-keyword'>if</span> <span class='hs-varid'>pred</span> <span class='hs-varid'>x</span> <span class='hs-keyword'>then</span> <span class='hs-varid'>return</span> <span class='hs-varid'>x</span> <span class='hs-keyword'>else</span> <span class='hs-varid'>fail</span> <span class='hs-str'>"Parse.satisfy: failed"</span>
<a name="line-100"></a> <span class='hs-layout'>}</span>
<a name="line-101"></a><span class='hs-comment'>------------------------------------------------------------------------</span>
<a name="line-102"></a><span class='hs-comment'>-- State handling</span>
<a name="line-103"></a>
<a name="line-104"></a><a name="stUpdate"></a><span class='hs-comment'>-- | Update the internal state.</span>
<a name="line-105"></a><span class='hs-definition'>stUpdate</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-varid'>s</span><span class='hs-keyglyph'>-></span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-conid'>()</span>
<a name="line-106"></a><span class='hs-definition'>stUpdate</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>
<a name="line-107"></a>
<a name="line-108"></a><a name="stQuery"></a><span class='hs-comment'>-- | Query the internal state.</span>
<a name="line-109"></a><span class='hs-definition'>stQuery</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-varid'>s</span><span class='hs-keyglyph'>-></span><span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>a</span>
<a name="line-110"></a><span class='hs-definition'>stQuery</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-111"></a>
<a name="line-112"></a><a name="stGet"></a><span class='hs-comment'>-- | Deliver the entire internal state.</span>
<a name="line-113"></a><span class='hs-definition'>stGet</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-varid'>s</span>
<a name="line-114"></a><span class='hs-definition'>stGet</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>ts</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-115"></a>
<a name="line-116"></a>
<a name="line-117"></a><a name="reparse"></a><span class='hs-comment'>------------------------------------------------------------------------</span>
<a name="line-118"></a><span class='hs-comment'>-- | Push some tokens back onto the front of the input stream and reparse.</span>
<a name="line-119"></a><span class='hs-comment'>-- This is useful e.g. for recursively expanding macros. When the</span>
<a name="line-120"></a><span class='hs-comment'>-- user-parser recognises a macro use, it can lookup the macro</span>
<a name="line-121"></a><span class='hs-comment'>-- expansion from the parse state, lex it, and then stuff the</span>
<a name="line-122"></a><span class='hs-comment'>-- lexed expansion back down into the parser.</span>
<a name="line-123"></a><span class='hs-definition'>reparse</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>t</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Parser</span> <span class='hs-varid'>s</span> <span class='hs-varid'>t</span> <span class='hs-conid'>()</span>
<a name="line-124"></a><span class='hs-definition'>reparse</span> <span class='hs-varid'>ts</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>P</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-varid'>inp</span><span class='hs-keyglyph'>-></span> <span class='hs-conid'>Success</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>ts</span><span class='hs-varop'>++</span><span class='hs-varid'>inp</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>
<a name="line-125"></a>
<a name="line-126"></a><span class='hs-comment'>------------------------------------------------------------------------</span>
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