├── .gitignore
├── LICENSE
├── README.md
├── calc.l
├── calc.y
└── makefile


/.gitignore:
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 1 | # Object files
 2 | *.o
 3 | *.ko
 4 | 
 5 | # Libraries
 6 | *.lib
 7 | *.a
 8 | 
 9 | # Shared objects (inc. Windows DLLs)
10 | *.dll
11 | *.so
12 | *.so.*
13 | *.dylib
14 | 
15 | # Executables
16 | *.exe
17 | *.out
18 | *.app
19 | 


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/LICENSE:
--------------------------------------------------------------------------------
 1 | MIT License
 2 | 
 3 | Copyright (c) 2018 Jonathan Engelsma
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 


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/README.md:
--------------------------------------------------------------------------------
1 | yacc-tutorial
2 | =============
3 | 
4 | This is the source code for my Yacc/Bison screencast tutorial on [YouTube](https://youtu.be/__-wUHG2rfM). 
5 | 


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/calc.l:
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 1 | %{
 2 | #include "y.tab.h"
 3 | void yyerror (char *s);
 4 | int yylex();
 5 | %}
 6 | %%
 7 | "print"				   {return print;}
 8 | "exit"				   {return exit_command;}
 9 | [a-zA-Z]			   {yylval.id = yytext[0]; return identifier;}
10 | [0-9]+                 {yylval.num = atoi(yytext); return number;}
11 | [ \t\n]                ;
12 | [-+=;]           	   {return yytext[0];}
13 | .                      {ECHO; yyerror ("unexpected character");}
14 | 
15 | %%
16 | int yywrap (void) {return 1;}
17 | 
18 | 


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/calc.y:
--------------------------------------------------------------------------------
 1 | %{
 2 | void yyerror (char *s);
 3 | int yylex();
 4 | #include <stdio.h>     /* C declarations used in actions */
 5 | #include <stdlib.h>
 6 | #include <ctype.h>
 7 | int symbols[52];
 8 | int symbolVal(char symbol);
 9 | void updateSymbolVal(char symbol, int val);
10 | %}
11 | 
12 | %union {int num; char id;}         /* Yacc definitions */
13 | %start line
14 | %token print
15 | %token exit_command
16 | %token <num> number
17 | %token <id> identifier
18 | %type <num> line exp term 
19 | %type <id> assignment
20 | 
21 | %%
22 | 
23 | /* descriptions of expected inputs     corresponding actions (in C) */
24 | 
25 | line    : assignment ';'		{;}
26 | 		| exit_command ';'		{exit(EXIT_SUCCESS);}
27 | 		| print exp ';'			{printf("Printing %d\n", $2);}
28 | 		| line assignment ';'	{;}
29 | 		| line print exp ';'	{printf("Printing %d\n", $3);}
30 | 		| line exit_command ';'	{exit(EXIT_SUCCESS);}
31 |         ;
32 | 
33 | assignment : identifier '=' exp  { updateSymbolVal($1,$3); }
34 | 			;
35 | exp    	: term                  {$$ = $1;}
36 |        	| exp '+' term          {$$ = $1 + $3;}
37 |        	| exp '-' term          {$$ = $1 - $3;}
38 |        	;
39 | term   	: number                {$$ = $1;}
40 | 		| identifier			{$$ = symbolVal($1);} 
41 |         ;
42 | 
43 | %%                     /* C code */
44 | 
45 | int computeSymbolIndex(char token)
46 | {
47 | 	int idx = -1;
48 | 	if(islower(token)) {
49 | 		idx = token - 'a' + 26;
50 | 	} else if(isupper(token)) {
51 | 		idx = token - 'A';
52 | 	}
53 | 	return idx;
54 | } 
55 | 
56 | /* returns the value of a given symbol */
57 | int symbolVal(char symbol)
58 | {
59 | 	int bucket = computeSymbolIndex(symbol);
60 | 	return symbols[bucket];
61 | }
62 | 
63 | /* updates the value of a given symbol */
64 | void updateSymbolVal(char symbol, int val)
65 | {
66 | 	int bucket = computeSymbolIndex(symbol);
67 | 	symbols[bucket] = val;
68 | }
69 | 
70 | int main (void) {
71 | 	/* init symbol table */
72 | 	int i;
73 | 	for(i=0; i<52; i++) {
74 | 		symbols[i] = 0;
75 | 	}
76 | 
77 | 	return yyparse ( );
78 | }
79 | 
80 | void yyerror (char *s) {fprintf (stderr, "%s\n", s);} 
81 | 
82 | 


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/makefile:
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 1 | calc: lex.yy.c y.tab.c
 2 | 	gcc -g lex.yy.c y.tab.c -o calc
 3 | 
 4 | lex.yy.c: y.tab.c calc.l
 5 | 	lex calc.l
 6 | 
 7 | y.tab.c: calc.y
 8 | 	yacc -d calc.y
 9 | 
10 | clean: 
11 | 	rm -rf lex.yy.c y.tab.c y.tab.h calc calc.dSYM
12 | 
13 | 


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