104 lines
2.1 KiB
HTML
104 lines
2.1 KiB
HTML
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<h2>Comments</h2>
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<pre><code>// Single-line comment
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/* Multi-line
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comment */</code></pre>
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<h2>C prologue and Bison declarations</h2>
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<pre><code>%{
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#include <stdio.h>
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#include <math.h>
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int yylex (void);
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void yyerror (char const *);
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%}
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%define api.value.type {double}
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%token NUM
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%union { char *string; }
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%%
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%%</code></pre>
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<h2>Grammar rules</h2>
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<pre><code>%%
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exp:
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NUM { $$ = $1; }
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| exp exp '+' { $$ = $1 + $2; }
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| exp exp '-' { $$ = $1 - $2; }
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| exp exp '*' { $$ = $1 * $2; }
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| exp exp '/' { $$ = $1 / $2; }
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| exp exp '^' { $$ = pow($1, $2); } /* Exponentiation */
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| exp 'n' { $$ = -$1; } /* Unary minus */
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;
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$@1: %empty { a(); };
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$@2: %empty { c(); };
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$@3: %empty { d(); };
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exp: $@1 "b" $@2 $@3 "e" { f(); };
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%%</code></pre>
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<h2>Full example</h2>
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<pre><code>/* Mini Calculator */
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/* calc.y */
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%{
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#include "heading.h"
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int yyerror(char *s);
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int yylex(void);
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%}
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%union{
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int int_val;
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string* op_val;
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}
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%start input
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%token <int_val> INTEGER_LITERAL
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%type <int_val> exp
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%left PLUS
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%left MULT
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%%
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input: /* empty */
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| exp { cout << "Result: " << $1 << endl; }
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;
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exp: INTEGER_LITERAL { $$ = $1; }
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| exp PLUS exp { $$ = $1 + $3; }
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| exp MULT exp { $$ = $1 * $3; }
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;
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%%
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int yyerror(string s)
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{
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extern int yylineno; // defined and maintained in lex.c
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extern char *yytext; // defined and maintained in lex.c
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cerr << "ERROR: " << s << " at symbol \"" << yytext;
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cerr << "\" on line " << yylineno << endl;
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exit(1);
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}
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int yyerror(char *s)
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{
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return yyerror(string(s));
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}</code></pre>
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<h2>Known failures</h2>
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<p>There are certain edge cases where Prism will fail.
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There are always such cases in every regex-based syntax highlighter.
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However, Prism dares to be open and honest about them.
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If a failure is listed here, it doesn’t mean it will never be fixed. This is more of a “known bugs” list, just with a certain type of bug.
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</p>
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<h3>Two levels of nesting inside C section</h3>
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<pre><code>{
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if($1) {
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if($2) {
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}
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}
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} // <- Broken
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%%
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%%</code></pre>
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