test.cmm
This is the input file.
int a = 5;
int b = 10;
int c = a + b;
return c;
manufacturing Which goes directly to myccompiler.exe
scan lexer.l
Here, the compiler starts tokenizing the text stream from test.cmm.
...
digit [0-9]
letter [a-zA-Z]
identifier {letter}({letter}|{digit})*
number -?{digit}+
float_number [0-9]*\.[0-9]+([eE][+-]?[0-9]+)?
scientific_number [0-9]+(\.[0-9]*)?[eE][+-]?[0-9]+
...
"int" { return INT; }
"=" { return ASSIGN; }
";" { return SEMICOLON; }
...
{identifier} {
yylval.sval = strdup(yytext);
return IDENTIFIER;
}
{number} {
yylval.ival = atoi(yytext);
return NUMBER;
}
...
Tokens:
INT IDENTIFIER ASSIGN NUMBER SEMICOLON INT IDENTIFIER ASSIGN NUMBER SEMICOLON INT IDENTIFIER ASSIGN IDENTIFIER PLUS IDENTIFIER SEMICOLON
parser.y
Next, the *ALICE compiler checks if the input stream of tokens is valid according to the grammar.
%token INT
%token PLUS ASSIGN SEMICOLON
%token sval IDENTIFIER
%token ival NUMBER
...
stmt:
IDENTIFIER ASSIGN expr SEMICOLON { $$ = create_node('=', NULL, $3, NULL, NULL, 0, 0.0, 0.0, $1); }
| RETURN expr SEMICOLON { $$ = create_node('R', $2, NULL, NULL, NULL, 0, 0.0, 0.0, NULL); }
expr:
expr PLUS expr { $$ = create_node('+', $1, $3, NULL, NULL, 0, 0.0, 0.0, NULL); }
...
Several nodes are created by the 'create_node' function. In this example, five productions/reductions are made:
decl: INT IDENTIFIER ASSIGN expr SEMICOLON { $$ = create_node('=', NULL, $4, NULL, NULL, 0, 0.0, 0.0, $2); } (3 times);
expr: expr PLUS expr { $$ = create_node('+', $1, $3, NULL, NULL, 0, 0.0, 0.0, NULL); }
stmt: RETURN expr SEMICOLON { $$ = create_node('R', $2, NULL, NULL, NULL, 0, 0.0, 0.0, NULL); }
decls: decls decl { $$ = create_node(';', $1, $2, NULL, NULL, 0, 0.0, 0.0, NULL); }
program: decls { $$ = create_node('RTN', $1, NULL, NULL, NULL, 0, 0.0, 0.0, NULL); generate_code_from_ast($$); }
ast.c
Finally, the *ALICE compiler generates the ASM output code based on the nodes created by the create_node function in the previous step.
ASTNode *create_node(int type, ASTNode *left, ASTNode *right, ASTNode *back, ASTNode *forth, int ival, float fval, double dval, char *sval)
{
ASTNode *node = (ASTNode *)malloc(sizeof(ASTNode));
node->type = type;
node->left = left;
node->right = right;
node->back = back;
node->forth = forth;
if (sval)
{
node->value.sval = strdup(sval);
}
else if (type == 'FL')
{
node->value.fval = fval;
}
else if (type == 'DB')
{
node->value.dval = dval;
}
else
{
node->value.ival = ival;
}
return node;
}
Nodes:
'N' (2x)
'=' (3x)
'I' (5x)
'+' (1x)
'R' (1x)
'RTN' (1x)
test.asm
This is the output file.
LOAD 5
SET a
LOAD 10
SET b
LOAD a
ADD b
SET c
PLD c
RETURN
ROOT
