Core Function Parser Engine
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Terminal("Name") | Terminal("Name") | ||
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Defines this class as the object to be created when this Terminal is found in the source code | Defines this class as the object to be created when this Terminal is found in the source code | ||
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<pre> | <pre> | ||
Rule("<rule> ::= <bla bla bla>") | Rule("<rule> ::= <bla bla bla>") | ||
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Defines this class as the object to be created when this Rule is found in the source code | Defines this class as the object to be created when this Rule is found in the source code | ||
Latest revision as of 12:37, 14 June 2015
[Rules/Terminals] : TokenName
Class name
{
Function __Construct ( <Parameters> ... )
{
statements
...
}
}
Contents |
Description
Parse text and have classes created and returned to you.
Terminal
Entered like:
Terminal("Name")
Defines this class as the object to be created when this Terminal is found in the source code
Rule
Entered like:
Rule("<rule> ::= <bla bla bla>")
Defines this class as the object to be created when this Rule is found in the source code
Class
The class object to be created
Function
Optional; If the __Construct is made then the Tokens will be linked to that class otherwise they may be null etc.
Remarks
This makes use of the GoldParser.
Its purpose is to provide a way to parse more complex files than simply regex alone can allow.
To make use of this you must first created a grammar file (.CGT) in GoldParser builder then create all classes for use (Simply opening parser without the rules/terminals will tell you what it requires to work) then use the Parser() function to spawn a new parser and Parse() to read text and parse it.
See example below
Example
[ Terminal("(EOF)") Terminal("(Error)") Terminal("(Whitespace)") Terminal("(") Terminal(")") ] : SpecialToken Class myUselessTerminals{}; [Terminal("Float")] : SpecialToken Class myFloat { my $value; Function __Construct( $Value ) { $this->$value = (Double)ObjToVar($Value); } }; [Terminal("Integer")] : SpecialToken Class myInteger { my $value; Function __Construct( $Value ) { $this->$value = (Double)ObjToVar($Value); } }; [Rule("<Negate Exp> ::= ~'-' <Value>")] : SpecialToken Class Negate { my $value; Function __Construct( $value ) { $this->$value = -(TokenClass($value)->$value); } }; [Terminal("+")] : SpecialToken Class opPlus { my $value; Function __Construct( ) { } Function Calculate(&$Left, $Right) { return TokenClass($Left)->$value += TokenClass($Right)->$value; } }; [Terminal("-")] : SpecialToken Class opMinus { my $value; Function __Construct( ) { } Function Calculate(&$Left, $Right) { return TokenClass($Left)->$value -= TokenClass($Right)->$value; } }; [Terminal("*")] : SpecialToken Class opMult { my $value; Function __Construct( ) { } Function Calculate(&$Left, $Right) { return TokenClass($Left)->$value *= TokenClass($Right)->$value; } }; [Terminal("/")] : SpecialToken Class opDivide { my $value; Function __Construct( ) { } Function Calculate(&$Left, $Right) { return TokenClass($Left)->$value /= TokenClass($Right)->$value; } }; [ Rule("<Expression> ::= <Expression> '+' <Mult Exp>") Rule("<Expression> ::= <Expression> '-' <Mult Exp>") Rule("<Mult Exp> ::= <Mult Exp> '/' <Negate Exp>") Rule("<Mult Exp> ::= <Mult Exp> '*' <Negate Exp>") ] : SpecialToken Class Operation { my $value; Function __Construct( $Left, $OP, $Right ) { $this->$value = TokenClass($OP)->Calculate(&$Left, $Right); } }; my $Trims = array( "<Value> ::= '(' <Expression> ')'" => "<Expression>" ); my $Parser = Parser("Test.cgt", "SpecialToken", $Trims); println("Enter expressions to be parsed."); println("Example 100+(50/2)"); while(true) { my $Input = input("> "); try { if(isEmpty($Input)) { println("You must type an expression to parse"); continue; } my $ReturnToken = Parse($Parser, $Input); if(isToken($ReturnToken)) { println(TokenClass($ReturnToken)->$Value); } } catch (Exception $e) { println("Error: " . $e->getMessage()); } }
Here is the Grammar file to use with the above source code
"Name" = 'Calculator Sample Grammar'
"Author" = 'Arsène von Wyss'
"Version" = '0.1'
"About" = 'Sample grammar for simple calculation expressions'
"Start Symbol" = <Expression>
"Case Sensitive" = false
Integer = {Digit}+
Float = {Digit}*'.'{Digit}+([Ee][+-]?{Digit}+)?
<Expression> ::= <Expression> '+' <Mult Exp>
| <Expression> '-' <Mult Exp>
| <Mult Exp>
<Mult Exp> ::= <Mult Exp> '*' <Negate Exp>
| <Mult Exp> '/' <Negate Exp>
| <Negate Exp>
<Negate Exp> ::= '-' <Value>
| <Value>
<Value> ::= Integer
| Float
| '(' <Expression> ')'
