You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
219 lines
5.3 KiB
219 lines
5.3 KiB
%{
|
|
|
|
/* compile: leg -o calc.c calc.leg
|
|
* cc -o calc calc.c
|
|
*
|
|
* run: echo "2+3" | ./calc
|
|
*/
|
|
|
|
|
|
#include <stdbool.h>
|
|
#include <sysexits.h>
|
|
#include <assert.h>
|
|
#include <gc.h> // NEVER, EVER HAVE TO CALL FREE (EVER) AGAIN (YES, REALLY)
|
|
#define malloc(n) GC_MALLOC(n)
|
|
#define realloc(o, n) GC_REALLOC(o, n)
|
|
|
|
typedef enum { Undefined, Integer, Symbol } type_t;
|
|
|
|
union object;
|
|
typedef union object *oop;
|
|
|
|
#define YYSTYPE oop
|
|
YYSTYPE yylval;
|
|
|
|
struct Undefined {
|
|
type_t type;
|
|
};
|
|
|
|
struct Integer {
|
|
type_t type;
|
|
int value;
|
|
};
|
|
|
|
struct Symbol {
|
|
type_t type;
|
|
char *name;
|
|
int defined;
|
|
oop value; // NULL
|
|
};
|
|
|
|
union object {
|
|
type_t type;
|
|
struct Undefined Undefined;
|
|
struct Integer Integer;
|
|
struct Symbol Symbol;
|
|
};
|
|
|
|
union object _null = { .Undefined = { Undefined } };
|
|
oop null = &_null;
|
|
|
|
oop _checkType(oop ptr, type_t type) {
|
|
assert(ptr->type == type);
|
|
return ptr;
|
|
}
|
|
|
|
#define get(PTR, TYPE, FIELD) _checkType(PTR, TYPE)->TYPE.FIELD
|
|
#define set(PTR, TYPE, FIELD, VALUE) _checkType(PTR, TYPE)->TYPE.FIELD = VALUE
|
|
|
|
void *memcheck(void *ptr)
|
|
{
|
|
if (NULL == ptr) {
|
|
fprintf(stderr, "Error: out of memory\n");
|
|
exit(EX_OSERR); // this is as close as we have for 'resource unavailable'
|
|
}
|
|
return ptr;
|
|
}
|
|
|
|
oop makeInteger(int value) {
|
|
oop newInt = memcheck(malloc(sizeof(union object)));
|
|
newInt->type = Integer;
|
|
newInt->Integer.value = value;
|
|
return newInt;
|
|
}
|
|
|
|
oop makeSymbol(char *name) {
|
|
oop newSymb = memcheck(malloc(sizeof(union object)));
|
|
newSymb->type = Symbol;
|
|
newSymb->Symbol.name = name;
|
|
newSymb->Symbol.defined = 0;
|
|
newSymb->Symbol.value = null;
|
|
return newSymb;
|
|
}
|
|
|
|
void print(oop ast) {
|
|
switch (ast->type) {
|
|
case Undefined:
|
|
printf("null");
|
|
return;
|
|
case Integer:
|
|
printf("%i", get(ast, Integer, value));
|
|
return;
|
|
case Symbol:
|
|
printf("%s=", get(ast, Symbol, name));
|
|
print(get(ast, Symbol, value));
|
|
return;
|
|
}
|
|
assert(0);
|
|
}
|
|
|
|
void println(oop ast)
|
|
{
|
|
print(ast);
|
|
printf("\n");
|
|
}
|
|
|
|
#define SYMBOL_TABLE_CHUNK 1024
|
|
|
|
typedef struct table_t {
|
|
oop *array;
|
|
size_t size;
|
|
size_t capacity;
|
|
} table_t;
|
|
|
|
#define TABLE_INITIALISER { NULL, 0, 0 } // first call to table_insert() will initialise storage
|
|
|
|
table_t table = TABLE_INITIALISER; // safe but not strictly needed on Unix because BSS segment is initialised to all zeroes
|
|
|
|
ssize_t table_search(table_t *table, char *ident)
|
|
{
|
|
ssize_t l = 0, r = table->size - 1;
|
|
while (l <= r) {
|
|
ssize_t mid = (l + r) / 2;
|
|
int cmpres = strcmp(get(table->array[mid], Symbol, name), ident);
|
|
if (cmpres > 0) r = mid - 1;
|
|
else if (cmpres < 0) l = mid + 1;
|
|
else return mid; // non-negative result => element found at this index
|
|
}
|
|
return -1 - l; // negative result => 'not found', reflected around -1 instead of 0 to allow 'not found' at index 0
|
|
}
|
|
|
|
// ssize_t result because -1 means 'error'
|
|
ssize_t table_insert(table_t *table, oop object, size_t pos)
|
|
{
|
|
// Should I use in my code a function starting with _ or is it a convention to prevent its usage ?
|
|
_checkType(object, Symbol);
|
|
if (pos > table->size) { // don't need to check for pos < 0 because size_t is unsigned
|
|
return -1;
|
|
}
|
|
|
|
if (table->size >= table->capacity) {
|
|
// on the first call table->array will be NULL and realloc() will behave like malloc()
|
|
table->array = memcheck(realloc(table->array, sizeof(oop) * (table->capacity + SYMBOL_TABLE_CHUNK)));
|
|
table->capacity += SYMBOL_TABLE_CHUNK;
|
|
}
|
|
|
|
memmove(table->array + pos + 1, table->array + pos, sizeof(*table->array) * (table->size - pos));
|
|
table->array[pos] = object;
|
|
return ++(table->size);
|
|
}
|
|
|
|
oop intern(char *ident)
|
|
{
|
|
ssize_t res= table_search(&table, ident); // < 0 => not found
|
|
if (res >= 0) return table.array[res];
|
|
res= -1 - res; // 'un-negate' the result by reflecting it around X=-1
|
|
oop new_symbol = makeSymbol(memcheck(strdup(ident)));
|
|
table_insert(&table, new_symbol, res);
|
|
return new_symbol;
|
|
}
|
|
|
|
oop update_symbol_value(oop symbol, oop integer)
|
|
{
|
|
_checkType(symbol, Symbol);
|
|
// For now it will fail with assigning to null
|
|
// because for now we can write "a=2 b=a" because everything is passed by value
|
|
_checkType(integer, Integer);
|
|
symbol->Symbol.value = integer;
|
|
return symbol;
|
|
}
|
|
|
|
%}
|
|
|
|
start = e:exp { yylval = e }
|
|
|
|
exp = - (a:assign { $$ = a }
|
|
| s:sum { $$ = s }
|
|
)
|
|
|
|
assign = l:IDENT EQUAL n:sum { $$ = update_symbol_value(l, n) }
|
|
|
|
sum = PLUS* l:prod
|
|
( PLUS+ r:prod { get(l, Integer, value) += get(r, Integer, value) }
|
|
| MINUS r:prod { get(l, Integer, value) -= get(r, Integer, value) }
|
|
)* { $$ = l }
|
|
|
|
prod = l:neg
|
|
( MULTI r:neg { get(l, Integer, value) *= get(r, Integer, value) }
|
|
| DIVIDE r:neg { get(l, Integer, value) /= get(r, Integer, value) }
|
|
| MODULO r:neg { get(l, Integer, value) %= get(r, Integer, value) }
|
|
)* { $$ = l }
|
|
|
|
neg = MINUS n:neg { set(n, Integer, value, -get(n, Integer, value)); $$ = n }
|
|
| n:value { $$ = n }
|
|
|
|
value = n:NUMBER { $$ = n }
|
|
| NULL { $$ = null; // For now it doesn't work because of _checktype in update_symbol_value() }
|
|
| l:IDENT { $$ = get(l, Symbol, value); // Will result in an assertion failed if ident is undefined }
|
|
|
|
- = [ \t]*
|
|
NUMBER = < [0-9]+ > - { $$ = makeInteger(atoi(yytext)) }
|
|
IDENT = < [a-zA-Z][a-zA-Z0-9_]* > - { $$ = intern(yytext) }
|
|
PLUS = '+' -
|
|
MINUS = '-' -
|
|
MULTI = '*' -
|
|
DIVIDE = '/' -
|
|
MODULO = '%' -
|
|
EQUAL = '=' -
|
|
NULL = 'null' -
|
|
|
|
%%
|
|
|
|
int main(int argc, char **argv)
|
|
{
|
|
while (yyparse()) {
|
|
println(yylval);
|
|
}
|
|
|
|
return 0;
|
|
}
|