From c7345482e39982e53a2aae1525632f8ebebb0529 Mon Sep 17 00:00:00 2001
From: Dimitar Trendafilov <dimitar@coherent-labs.com>
Date: Fri, 28 Sep 2018 01:35:30 +0300
Subject: Flex-based lexer for JavaScript

---
 demo/flex/JavaScript.flex | 67 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 demo/flex/JavaScript.flex

(limited to 'demo/flex/JavaScript.flex')

diff --git a/demo/flex/JavaScript.flex b/demo/flex/JavaScript.flex
new file mode 100644
index 0000000..4df5ca3
--- /dev/null
+++ b/demo/flex/JavaScript.flex
@@ -0,0 +1,67 @@
+/* scanner for a toy JavaScript-like language */
+
+%{
+/* need this for the call to atof() below */
+#include <math.h>
+%}
+
+DIGIT    [0-9]
+ID       [a-z_$][a-z0-9_$]*
+STRQ     '([^\']|(\\\'))*'
+STRDQ    "([^\"]|(\\\"))*"
+
+%%
+
+{DIGIT}+    {
+            printf( "An integer: %s (%d)\n", yytext,
+                    atoi( yytext ) );
+            }
+
+{DIGIT}+"."{DIGIT}*        {
+            printf( "A float: %s (%g)\n", yytext,
+                    atof( yytext ) );
+            }
+
+if|else|for|while|do|break|switch|case|function|return|new|delete|try|throw|catch|class|public|private {
+    printf( "A keyword: %s\n", yytext );
+}
+
+{ID}        printf( "An identifier: %s\n", yytext );
+{STRQ}|{STRDQ}        printf( "A string: %s\n", yytext );
+
+"."|"+"|"-"|"*"|"/"|"="|"!"|">"|"<"|"!=="|"==="|">="|"<="|"++"|"--"|"=>"   printf( "An operator: %s\n", yytext );
+
+";"   printf( "A semicolumn\n" );
+"("   printf( "A left parenthesis\n" );
+")"   printf( "A right parenthesis\n" );
+"{"   printf( "A left bracket\n" );
+"}"   printf( "A right bracket\n" );
+":"   printf( "A colon\n" );
+"?"   printf( "A question mark\n" );
+
+[ \t\n]+          /* eat up whitespace */
+
+.           printf( "Unrecognized character: %s\n", yytext );
+
+%%
+
+int yywrap()
+{
+    return 1;
+}
+
+
+int main(int argc, const char* argv[])
+{
+    ++argv, --argc;  /* skip over program name */
+    if ( argc > 0 )
+            yyin = fopen( argv[0], "r" );
+    else
+            yyin = stdin;
+
+    /* YY_BUFFER_STATE hello = yy_scan_string("(x)=>{ return x !== 1; }"); */
+    /* yypush_buffer_state(hello); */
+    yylex();
+    /* yy_delete_buffer(hello); */
+    return 0;
+}
-- 
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