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POAntlr4 Grammar/Rules - issue with solving BASIC print variable
 

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  1. POAntlr4 Grammar/Rules - issue with solving BASIC print variable
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    <p>The scenario is that I want to create a BASIC (high level) language using ANTRL4.</p> <p>The test input below is the creation of a variable called C$ and assigning an integer value. The value assignment works. The print statement works except where concatenating the variable to it:-</p> <pre><code> ************ TEST CASE **************** </code></pre> <p>$C=15;</p> <p>print "dangerdanger!"; # print works</p> <p>print "Number of GB left=" + $C;</p> <p><img src="https://i.stack.imgur.com/yHMQ0.png" alt="Parse Tree Inspector"></p> <p>Using a Parse Tree Inspector I can see assignments are working fine but when it gets to the identification of the variable in the string it seems there is a mismatched input '+' expecting STMTEND.</p> <p>I wondered if anyone could help me out here and see what adjustment I need to make to my rules and grammar to solve this issue.</p> <p>Many thanks in advance.</p> <p>Kevin PS. As a side issue I would rather have C$ than $C but early days...</p> <pre><code>********RULES************ VARNAME : '$'('A'..'Z')* ; CONCAT : '+' ; STMTEND : SEMICOLON NEWLINE* | NEWLINE+ ; STRING : SQUOTED_STRING (CONCAT SQUOTED_STRING | CONCAT VARNAME)* | DQUOTED_STRING (CONCAT DQUOTED_STRING | CONCAT VARNAME)* ; fragment SQUOTED_STRING : '\'' (~['])* '\'' ; fragment DQUOTED_STRING : '"' ( ESC_SEQ| ~('\\'|'"') )* '"' ; fragment ESC_SEQ : '\\' ('b'|'t'|'n'|'f'|'r'|'\"'|'\''|'\\') | UNICODE_ESC | OCTAL_ESC ; fragment OCTAL_ESC : '\\' ('0'..'3') ('0'..'7') ('0'..'7') | '\\' ('0'..'7') ('0'..'7') | '\\' ('0'..'7') ; fragment HEX_DIGIT : '0x' ('0'..'9' | 'a'..'f' | 'A'..'F')+ ; fragment UNICODE_ESC : '\\' 'u' HEX_DIGIT HEX_DIGIT HEX_DIGIT HEX_DIGIT ; SEMICOLON : ';' ; NEWLINE : '\r'?'\n' ************GRAMMAR************ print_command : PRINT STRING STMTEND #printCommandLabel ; assignment : VARNAME EQUALS INTEGER STMTEND #assignInteger | VARNAME EQUALS STRING STMTEND #assignString ; </code></pre>
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