/ elang / kernel

Ignore Pattern

The ignore pattern always successfully matches against anything and does nothing.

BNF:	"_"
XML DTD:	<!ELEMENT ignorePattern EMPTY>
Java:	Pattern match implicitly succeeds without generating any code
Example:	Checks that we have a pair while extracting the first element and ignoring the second element. def [first, _] := pair
in Kernel-E:	def [first :any, _] := pair
in XML:	<defineExpr> <listPattern> <finalPattern> <Noun>first</Noun> <Noun>any</Noun> </finalPattern> <ignorePattern/> </listPattern> <Noun>pair</Noun> </defineExpr>
in Java:	Object specimen = pair; if (!isList(specimen)) { throw(...); } Integer len = E.toInteger(E.call(specimen, "size")); if (len.intValue() != 2) { throw(...); } final Object first = E.call(specimen, "get", 0); # we hope to optimize this out this last useless call E.call(specimen, "get", 1);