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Overview

Pattern matching for D

Description

• match and disasemble Tuple,Range,Array,Struct,Class.
• Suport guard expression.
• Tagged Variant

Example

sample code

this code doesn't work now.

int add_all(int[] list){
	mixin(pmatch!(list,q{
		[] => return 0;
		[x] ~ xs => x + return add_all(xs);
	}));
}

sample pattern

InputRange

x::xs
[]
x::[]

Array

[]
[x]
[x,_]
[x] ~ xs
xs ~ [x]

Tuple

[x,_]
[x,y]

Class and Struct

{x = alpha}
{x = alpha,y = beta}

std.variant.Algebraic and Variant

x:int
[x]~xs : real[]
[x:int[]]~xs

Input Range

x::xs
x::y::xs

Tagged Variant

x:Num
[x]~xs:Array
[x:Num]~xs

Complex

[(x,_)] ~ xs
{[x]~_ : alpha,{z : theta} : beta}
{Num x : theta}

Sytax difination

strings literal, charcter literal, floating point literal and interger literal are defined as 'literal'. Allowed Identifier names are defined as 'identifier'

PEG

                   bind <- identifier
				   rval <- literal
                 record <- '{' patterns '=' identifier (',' patterns '=' identifier)* '}'
                bracket <- patterns
variant_accept_patterns <- array | record | bind
                variant <- variant_accept_patterns ':' identifier
     as_accept_patterns <- record | bracket | record | variant | bind | rval
                     as <- as_accept_patterns ('@' as_accept_patterns)+
  range_accept_patterns <- as | array | variant | record | bind
                  range <- (range_accept_patterns "::")+ bind
          array_element <- '[' (patterns (',' patterns)+)? ']'
                  array <- ((array_element | bind) ('~' (array_element | bind))+) | array_element
               patterns <- as | array | range | variant | record | bind | rval | "[]"

BNF

         bind ::= identifier
         rval ::= literal
       record ::= '{' patterns '=' identifier (',' patterns '=' identifier)* '}'
      bracket ::= '(' patterns ')'
      variant ::= (array | record | bracket | bind | rval) ':' identifier
           as ::= patterns ('@' patterns)+
        range ::= (patterns "::")+ identifier
array_element ::= '[' (patterns (',' patterns)*)? ']'
        array ::= (array_element | bind) ('~' (array_element | bind))*
	 patterns ::= as | range | array | variant | record | bracket | bind | rval