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Move type definitions to the program node

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Eugen Wissner
2025-01-12 10:35:24 +01:00
parent 7985704981
commit b45b00a3f6
11 changed files with 236 additions and 82 deletions
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README
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@ -1,37 +1,73 @@
# Elna programming language
Elna compiles simple mathematical operations to machine code.
The compiled program returns the result of the operation.
Elna is a simple, imperative, low-level programming language.
It is intendet to accompany other languages in the areas, where a high-level
language doesn't fit well. It is also supposed to be an intermediate
representation for a such high-level hypothetical programming language.
## File extension
.elna
## Grammar PL/0
## Current implementation
program = block "." ;
This repository contains a GCC frontend for Elna. After finishing the frontend
I'm planning to rewrite the compiler in Elna itself with its own backend and
a hand-written parser. So GCC gives a way to have a simple bootstrap compiler
and a possbility to compile Elna programs for different platforms.
block = [ "const" ident "=" number {"," ident "=" number} ";"]
[ "var" ident {"," ident} ";"]
{ "procedure" ident ";" block ";" } statement ;
## Grammar
statement = [ ident ":=" expression | "call" ident
| "?" ident | "!" expression
| "begin" statement {";" statement } "end"
| "if" condition "then" statement
| "while" condition "do" statement ];
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9";
integer = digit { digit };
boolean = "true" | "false";
program = [ "type" type_definitions ";" ]
[ "const" ident "=" integer { "," ident "=" integer } ";"]
{ procedure_definition }
[ "var" variable_declarations ";" ]
compound_statement ".";
procedure_definition = "procedure" ident formal_parameter_list ";" block ";";
block = [ "const" ident "=" integer { "," ident "=" integer } ";" ]
[ "var" variable_declarations ";" ]
statement;
statement = [ ident ":=" expression
| ident actual_parameter_list
| compound_statement
| "if" condition "then" statement
| "while" condition "do" statement ];
compound_statement = "begin" statement {";" statement } "end" ;
condition = "odd" expression |
expression ("="|"#"|"<"|"<="|">"|">=") expression ;
expression ("="|"#"|"<"|"<="|">"|">=") expression;
expression = [ "+"|"-"] term { ("+"|"-") term};
term = factor {("*"|"/") factor};
term = factor { ("*"|"/") factor };
factor = ident | number | "(" expression ")";
factor = ident | integer | "(" expression ")";
## Operations
formal_parameter_list = "(" [ variable_declarations ] ")";
"!" - Write a line.
"?" - Read user input.
"odd" - The only function, returns whether a number is odd.
actual_parameter_list = "(" [ expressions ] ")";
expressions = expression { "," expression };
variable_declarations = variable_declaration { ";" variable_declaration };
variable_declaration = ident ":" type_expression;
type_expression = "array" integer "of" type_expression
| "^" type_expression
| "record" field_list "end"
| ident;
field_list = field_declaration { ";" field_declaration };
field_declaration = ident ":" type_expression;