74 lines
2.2 KiB
Plaintext
74 lines
2.2 KiB
Plaintext
# Elna programming language
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Elna is a simple, imperative, low-level programming language.
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It is intendet to accompany other languages in the areas, where a high-level
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language doesn't fit well. It is also supposed to be an intermediate
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representation for a such high-level hypothetical programming language.
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## File extension
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.elna
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## Current implementation
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This repository contains a GCC frontend for Elna. After finishing the frontend
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I'm planning to rewrite the compiler in Elna itself with its own backend and
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a hand-written parser. So GCC gives a way to have a simple bootstrap compiler
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and a possbility to compile Elna programs for different platforms.
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## Grammar
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digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9";
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integer = digit { digit };
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boolean = "true" | "false";
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program = [ "type" type_definitions ";" ]
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[ "const" ident "=" integer { "," ident "=" integer } ";"]
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{ procedure_definition }
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[ "var" variable_declarations ";" ]
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compound_statement ".";
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procedure_definition = "procedure" ident formal_parameter_list ";" block ";";
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block = [ "const" ident "=" integer { "," ident "=" integer } ";" ]
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[ "var" variable_declarations ";" ]
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statement;
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statement = [ ident ":=" expression
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| ident actual_parameter_list
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| compound_statement
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| "if" condition "then" statement
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| "while" condition "do" statement ];
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compound_statement = "begin" statement {";" statement } "end" ;
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condition = "odd" expression |
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expression ("="|"#"|"<"|"<="|">"|">=") expression;
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expression = [ "+"|"-"] term { ("+"|"-") term};
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term = factor { ("*"|"/") factor };
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factor = ident | integer | "(" expression ")";
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formal_parameter_list = "(" [ variable_declarations ] ")";
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actual_parameter_list = "(" [ expressions ] ")";
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expressions = expression { "," expression };
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variable_declarations = variable_declaration { ";" variable_declaration };
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variable_declaration = ident ":" type_expression;
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type_expression = "array" integer "of" type_expression
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| "^" type_expression
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| "record" field_list "end"
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| ident;
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field_list = field_declaration { ";" field_declaration };
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field_declaration = ident ":" type_expression;
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