- "blocks" of multiple statements.
- `pass`: a statement which does nothing.
- - expressions: `+`, `-`, `*`, `/` can apply to numbers and `++` can
+ - expressions: `+`, `-`, `*`, `/`, `%` can apply to numbers and `++` can
catenate strings. `and`, `or`, `not` manipulate Booleans, and
normal comparison operators can work on all three types.
- `print`: will print the values in a list of expressions.
return rv;
}
+###### forward decls
+
+ static void free_value(struct value v);
+ static int type_compat(struct type *require, struct type *have, int rules);
+ static void type_print(struct type *type, FILE *f);
+ static struct value val_init(struct type *type);
+ static struct value dup_value(struct value v);
+ static int value_cmp(struct value left, struct value right);
+ static void print_value(struct value v);
+ static struct value parse_value(struct type *type, char *arg);
+
###### free context types
while (context.typelist) {
static int __fput_loc(struct exec *loc, FILE *f)
{
+ if (!loc)
+ return 0;
if (loc->line >= 0) {
fprintf(f, "%d:%d: ", loc->line, loc->column);
return 1;
###### ast
- enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1};
+ enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 2<<1};
###### format cases
case 'r':
###### core functions
+ struct lrval {
+ struct value val, *lval;
+ };
+
+ static struct lrval _interp_exec(struct exec *e);
+
static struct value interp_exec(struct exec *e)
{
- struct value rv;
+ struct lrval ret = _interp_exec(e);
+
+ if (ret.lval)
+ return dup_value(*ret.lval);
+ else
+ return ret.val;
+ }
+
+ static struct value *linterp_exec(struct exec *e)
+ {
+ struct lrval ret = _interp_exec(e);
+
+ return ret.lval;
+ }
+
+ static struct lrval _interp_exec(struct exec *e)
+ {
+ struct lrval ret;
+ struct value rv, *lrv = NULL;
rv.type = Tnone;
- if (!e)
- return rv;
+ if (!e) {
+ ret.lval = lrv;
+ ret.val = rv;
+ return ret;
+ }
switch(e->type) {
case Xbinode:
{
struct binode *b = cast(binode, e);
- struct value left, right;
+ struct value left, right, *lleft;
left.type = right.type = Tnone;
switch (b->op) {
## interp binode cases
}
## interp exec cases
}
- return rv;
+ ret.lval = lrv;
+ ret.val = rv;
+ return ret;
}
## Language elements
###### interp exec cases
case Xval:
- return dup_value(cast(val, e)->val);
+ rv = dup_value(cast(val, e)->val);
+ break;
###### ast functions
static void free_val(struct val *v)
}
} }$
+ $*exec
Variable -> IDENTIFIER ${ {
struct variable *v = var_ref(config2context(config), $1.txt);
$0 = new_pos(var, $1);
v->where_set = $0;
}
}
- $0->var = v;
+ cast(var, $0)->var = v;
} }$
+ ## variable grammar
$*type
Type -> IDENTIFIER ${
$0 = Tnone;
}
}$
+ ## type grammar
###### print exec cases
case Xvar:
}
if (v->merged)
v = v->merged;
+ if (v->constant && (rules & Rnoconstant)) {
+ type_err(c, "error: Cannot assign to a constant: %v",
+ prog, NULL, 0, NULL);
+ type_err(c, "info: name was defined as a constant here",
+ v->where_decl, NULL, 0, NULL);
+ *ok = 0;
+ return v->val.type;
+ }
if (v->val.type == NULL) {
if (type && *ok != 0) {
v->val = val_prepare(type);
if (v->merged)
v = v->merged;
- return dup_value(v->val);
+ lrv = &v->val;
+ break;
}
###### ast functions
###### free exec cases
case Xvar: free_var(cast(var, e)); break;
+### Expressions: Conditional
+
+Our first user of the `binode` will be conditional expressions, which
+is a bit odd as they actually have three components. That will be
+handled by having 2 binodes for each expression. The conditional
+expression is the lowest precedence operatior, so it gets to define
+what an "Expression" is. The next level up is "BoolExpr", which
+comes next.
+
+Conditional expressions are of the form "value `if` condition `else`
+other_value". There is no associativite with this operator: the
+values and conditions can only be other conditional expressions if
+they are enclosed in parentheses. Allowing nesting without
+parentheses would be too confusing.
+
+###### Binode types
+ CondExpr,
+
+###### Grammar
+
+ $*exec
+ Expression -> BoolExpr if BoolExpr else BoolExpr ${ {
+ struct binode *b1 = new(binode);
+ struct binode *b2 = new(binode);
+ b1->op = CondExpr;
+ b1->left = $<3;
+ b1->right = b2;
+ b2->op = CondExpr;
+ b2->left = $<1;
+ b2->right = $<5;
+ $0 = b1;
+ } }$
+ | BoolExpr ${ $0 = $<1; }$
+
+###### print binode cases
+
+ case CondExpr:
+ b2 = cast(binode, b->right);
+ print_exec(b2->left, -1, 0);
+ printf(" if ");
+ print_exec(b->left, -1, 0);
+ printf(" else ");
+ print_exec(b2->right, -1, 0);
+ break;
+
+###### propagate binode cases
+
+ case CondExpr: {
+ /* cond must be Tbool, others must match */
+ struct binode *b2 = cast(binode, b->right);
+ struct type *t2;
+
+ propagate_types(b->left, c, ok, Tbool, 0);
+ t = propagate_types(b2->left, c, ok, type, Rnolabel);
+ t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
+ return t ?: t2;
+ }
+
+###### interp binode cases
+
+ case CondExpr: {
+ struct binode *b2 = cast(binode, b->right);
+ left = interp_exec(b->left);
+ if (left.bool)
+ rv = interp_exec(b2->left);
+ else
+ rv = interp_exec(b2->right);
+ }
+ break;
+
### Expressions: Boolean
-Our first user of the `binode` will be expressions, and particularly
-Boolean expressions. As I haven't implemented precedence in the
-parser generator yet, we need different names for each precedence
-level used by expressions. The outer most or lowest level precedence
-are Boolean `or` `and`, and `not` which form an `Expression` out of `BTerm`s
-and `BFact`s.
+The next class of expressions to use the `binode` will be Boolean
+expressions. As I haven't implemented precedence in the parser
+generator yet, we need different names for each precedence level used
+by expressions. The outer most or lowest level precedence are
+conditional expressions are Boolean operators which form an `BoolExpr`
+out of `BTerm`s and `BFact`s. As well as `or` `and`, and `not` we
+have `and then` and `or else` which only evaluate the second operand
+if the result would make a difference.
###### Binode types
And,
+ AndThen,
Or,
+ OrElse,
Not,
###### Grammar
$*exec
- Expression -> Expression or BTerm ${ {
+ BoolExpr -> BoolExpr or BTerm ${ {
struct binode *b = new(binode);
b->op = Or;
b->left = $<1;
b->right = $<3;
$0 = b;
} }$
+ | BoolExpr or else BTerm ${ {
+ struct binode *b = new(binode);
+ b->op = OrElse;
+ b->left = $<1;
+ b->right = $<4;
+ $0 = b;
+ } }$
| BTerm ${ $0 = $<1; }$
BTerm -> BTerm and BFact ${ {
b->right = $<3;
$0 = b;
} }$
+ | BTerm and then BFact ${ {
+ struct binode *b = new(binode);
+ b->op = AndThen;
+ b->left = $<1;
+ b->right = $<4;
+ $0 = b;
+ } }$
| BFact ${ $0 = $<1; }$
BFact -> not BFact ${ {
printf(" and ");
print_exec(b->right, -1, 0);
break;
+ case AndThen:
+ print_exec(b->left, -1, 0);
+ printf(" and then ");
+ print_exec(b->right, -1, 0);
+ break;
case Or:
print_exec(b->left, -1, 0);
printf(" or ");
print_exec(b->right, -1, 0);
break;
+ case OrElse:
+ print_exec(b->left, -1, 0);
+ printf(" or else ");
+ print_exec(b->right, -1, 0);
+ break;
case Not:
printf("not ");
print_exec(b->right, -1, 0);
###### propagate binode cases
case And:
+ case AndThen:
case Or:
+ case OrElse:
case Not:
/* both must be Tbool, result is Tbool */
propagate_types(b->left, c, ok, Tbool, 0);
right = interp_exec(b->right);
rv.bool = rv.bool && right.bool;
break;
+ case AndThen:
+ rv = interp_exec(b->left);
+ if (rv.bool)
+ rv = interp_exec(b->right);
+ break;
case Or:
rv = interp_exec(b->left);
right = interp_exec(b->right);
rv.bool = rv.bool || right.bool;
break;
+ case OrElse:
+ rv = interp_exec(b->left);
+ if (!rv.bool)
+ rv = interp_exec(b->right);
+ break;
case Not:
rv = interp_exec(b->right);
rv.bool = !rv.bool;
###### Binode types
Plus, Minus,
- Times, Divide,
+ Times, Divide, Rem,
Concat,
Absolute, Negate,
Bracket,
Top -> * ${ $0.op = Times; }$
| / ${ $0.op = Divide; }$
+ | % ${ $0.op = Rem; }$
| ++ ${ $0.op = Concat; }$
###### print binode cases
case Times:
case Divide:
case Concat:
+ case Rem:
print_exec(b->left, indent, 0);
switch(b->op) {
- case Plus: printf(" + "); break;
- case Minus: printf(" - "); break;
- case Times: printf(" * "); break;
- case Divide: printf(" / "); break;
- case Concat: printf(" ++ "); break;
+ case Plus: fputs(" + ", stdout); break;
+ case Minus: fputs(" - ", stdout); break;
+ case Times: fputs(" * ", stdout); break;
+ case Divide: fputs(" / ", stdout); break;
+ case Rem: fputs(" % ", stdout); break;
+ case Concat: fputs(" ++ ", stdout); break;
default: abort();
}
print_exec(b->right, indent, 0);
case Plus:
case Minus:
case Times:
+ case Rem:
case Divide:
/* both must be numbers, result is Tnum */
case Absolute:
right = interp_exec(b->right);
mpq_div(rv.num, rv.num, right.num);
break;
+ case Rem: {
+ mpz_t l, r, rem;
+
+ left = interp_exec(b->left);
+ right = interp_exec(b->right);
+ mpz_init(l); mpz_init(r); mpz_init(rem);
+ mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
+ mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
+ mpz_tdiv_r(rem, l, r);
+ rv = val_init(Tnum);
+ mpq_set_z(rv.num, rem);
+ mpz_clear(r); mpz_clear(l); mpz_clear(rem);
+ break;
+ }
case Negate:
rv = interp_exec(b->right);
mpq_neg(rv.num, rv.num);
Declare,
###### SimpleStatement Grammar
- | Variable = Expression ${ {
- struct var *v = cast(var, $1);
-
+ | Variable = Expression ${
$0 = new(binode);
$0->op = Assign;
$0->left = $<1;
$0->right = $<3;
- if (v->var && v->var->constant) {
- type_err(config2context(config), "Cannot assign to a constant: %v",
- $0->left, NULL, 0, NULL);
- type_err(config2context(config), "name was defined as a constant here",
- v->var->where_decl, NULL, 0, NULL);
- }
- } }$
+ }$
| VariableDecl = Expression ${
$0 = new(binode);
$0->op = Declare;
case Declare:
/* Both must match and not be labels,
* Type must support 'dup',
- * result is Tnone */
- t = propagate_types(b->left, c, ok, NULL, Rnolabel);
+ * For Assign, left must not be constant.
+ * result is Tnone
+ */
+ t = propagate_types(b->left, c, ok, NULL,
+ Rnolabel | (b->op == Assign ? Rnoconstant : 0));
if (!b->right)
return Tnone;
} else {
t = propagate_types(b->right, c, ok, NULL, Rnolabel);
if (t)
- propagate_types(b->left, c, ok, t, 0);
+ propagate_types(b->left, c, ok, t,
+ (b->op == Assign ? Rnoconstant : 0));
}
if (t && t->dup == NULL) {
type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
###### interp binode cases
case Assign:
- {
- struct variable *v = cast(var, b->left)->var;
- if (v->merged)
- v = v->merged;
+ lleft = linterp_exec(b->left);
right = interp_exec(b->right);
- free_value(v->val);
- v->val = right;
+ if (lleft) {
+ free_value(*lleft);
+ *lleft = right;
+ } else
+ free_value(right);
right.type = NULL;
break;
- }
case Declare:
{
interp_exec(c->dopart);
if (c->thenpart) {
- v = interp_exec(c->thenpart);
- if (v.type != Tnone || !c->dopart)
- return v;
- free_value(v);
+ rv = interp_exec(c->thenpart);
+ if (rv.type != Tnone || !c->dopart)
+ goto Xcond_done;
+ free_value(rv);
}
} while (c->dopart);
if (value_cmp(v, cnd) == 0) {
free_value(v);
free_value(cnd);
- return interp_exec(cp->action);
+ rv = interp_exec(cp->action);
+ goto Xcond_done;
}
free_value(v);
}
free_value(cnd);
if (c->elsepart)
- return interp_exec(c->elsepart);
- v.type = Tnone;
- return v;
+ rv = interp_exec(c->elsepart);
+ else
+ rv.type = Tnone;
+ Xcond_done:
+ break;
+ }
+
+## Complex types
+
+Now that we have the shape of the interpreter in place we can add some
+complex types and connected them in to the data structures and the
+different phases of parse, analyse, print, interpret.
+
+For now, just arrays.
+
+### Arrays
+
+Arrays can be declared by giving a size and a type, as `[size]type' so
+`freq:[26]number` declares `freq` to be an array of 26 numbers. The
+size can be an arbitrary expression which is evaluated when the name
+comes into scope.
+
+Arrays cannot be assigned. When pointers are introduced we will also
+introduce array slices which can refer to part or all of an array -
+the assignment syntax will create a slice. For now, an array can only
+ever be referenced by the name it is declared with. It is likely that
+a "`copy`" primitive will eventually be define which can be used to
+make a copy of an array with controllable depth.
+
+###### type union fields
+
+ struct {
+ int size;
+ struct variable *vsize;
+ struct type *member;
+ } array;
+
+###### value union fields
+ struct {
+ struct value *elmnts;
+ } array;
+
+###### value functions
+
+ static struct value array_prepare(struct type *type)
+ {
+ struct value ret;
+
+ ret.type = type;
+ ret.array.elmnts = NULL;
+ return ret;
+ }
+
+ static struct value array_init(struct type *type)
+ {
+ struct value ret;
+ int i;
+
+ ret.type = type;
+ if (type->array.vsize) {
+ mpz_t q;
+ mpz_init(q);
+ mpz_tdiv_q(q, mpq_numref(type->array.vsize->val.num),
+ mpq_denref(type->array.vsize->val.num));
+ type->array.size = mpz_get_si(q);
+ mpz_clear(q);
+ }
+ ret.array.elmnts = calloc(type->array.size,
+ sizeof(ret.array.elmnts[0]));
+ for (i = 0; ret.array.elmnts && i < type->array.size; i++)
+ ret.array.elmnts[i] = val_init(type->array.member);
+ return ret;
+ }
+
+ static void array_free(struct value val)
+ {
+ int i;
+
+ if (val.array.elmnts)
+ for (i = 0; i < val.type->array.size; i++)
+ free_value(val.array.elmnts[i]);
+ free(val.array.elmnts);
+ }
+
+ static int array_compat(struct type *require, struct type *have)
+ {
+ if (have->compat != require->compat)
+ return 0;
+ /* Both are arrays, so we can look at details */
+ if (!type_compat(require->array.member, have->array.member, 0))
+ return 0;
+ if (require->array.vsize == NULL && have->array.vsize == NULL)
+ return require->array.size == have->array.size;
+
+ return require->array.vsize == have->array.vsize;
+ }
+
+ static void array_print_type(struct type *type, FILE *f)
+ {
+ fputs("[", f);
+ if (type->array.vsize) {
+ struct binding *b = type->array.vsize->name;
+ fprintf(f, "%.*s]", b->name.len, b->name.txt);
+ } else
+ fprintf(f, "%d]", type->array.size);
+ type_print(type->array.member, f);
+ }
+
+ static struct type array_prototype = {
+ .prepare = array_prepare,
+ .init = array_init,
+ .print_type = array_print_type,
+ .compat = array_compat,
+ .free = array_free,
+ };
+
+###### type grammar
+
+ | [ NUMBER ] Type ${
+ $0 = calloc(1, sizeof(struct type));
+ *($0) = array_prototype;
+ $0->array.member = $<4;
+ $0->array.vsize = NULL;
+ {
+ struct parse_context *c = config2context(config);
+ char tail[3];
+ mpq_t num;
+ if (number_parse(num, tail, $2.txt) == 0)
+ tok_err(c, "error: unrecognised number", &$2);
+ else if (tail[0])
+ tok_err(c, "error: unsupported number suffix", &$2);
+ else {
+ $0->array.size = mpz_get_ui(mpq_numref(num));
+ if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
+ tok_err(c, "error: array size must be an integer",
+ &$2);
+ } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
+ tok_err(c, "error: array size is too large",
+ &$2);
+ mpq_clear(num);
+ }
+ $0->next= c->anon_typelist;
+ c->anon_typelist = $0;
+ }
+ }$
+
+ | [ IDENTIFIER ] Type ${ {
+ struct parse_context *c = config2context(config);
+ struct variable *v = var_ref(c, $2.txt);
+
+ if (!v)
+ tok_err(config2context(config), "error: name undeclared", &$2);
+ else if (!v->constant)
+ tok_err(config2context(config), "error: array size must be a constant", &$2);
+
+ $0 = calloc(1, sizeof(struct type));
+ *($0) = array_prototype;
+ $0->array.member = $<4;
+ $0->array.size = 0;
+ $0->array.vsize = v;
+ $0->next= c->anon_typelist;
+ c->anon_typelist = $0;
+ } }$
+
+###### parse context
+
+ struct type *anon_typelist;
+
+###### free context types
+
+ while (context.anon_typelist) {
+ struct type *t = context.anon_typelist;
+
+ context.anon_typelist = t->next;
+ free(t);
+ }
+
+###### Binode types
+ Index,
+
+###### variable grammar
+
+ | Variable [ Expression ] ${ {
+ struct binode *b = new(binode);
+ b->op = Index;
+ b->left = $<1;
+ b->right = $<3;
+ $0 = b;
+ } }$
+
+###### print binode cases
+ case Index:
+ print_exec(b->left, -1, 0);
+ printf("[");
+ print_exec(b->right, -1, 0);
+ printf("]");
+ break;
+
+###### propagate binode cases
+ case Index:
+ /* left must be an array, right must be a number,
+ * result is the member type of the array
+ */
+ propagate_types(b->right, c, ok, Tnum, 0);
+ t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
+ if (!t || t->compat != array_compat) {
+ type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
+ *ok = 0;
+ return NULL;
+ } else {
+ if (!type_compat(type, t->array.member, rules)) {
+ type_err(c, "error: have %1 but need %2", prog,
+ t->array.member, rules, type);
+ *ok = 0;
+ }
+ return t->array.member;
+ }
+ break;
+
+###### interp binode cases
+ case Index: {
+ mpz_t q;
+ long i;
+
+ lleft = linterp_exec(b->left);
+ right = interp_exec(b->right);
+ mpz_init(q);
+ mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
+ i = mpz_get_si(q);
+ mpz_clear(q);
+
+ if (i >= 0 && i < lleft->type->array.size)
+ lrv = &lleft->array.elmnts[i];
+ else
+ rv = val_init(lleft->type->array.member);
+ break;
}
### Finally the whole program.
/* If a variable is not used after the 'if', no
* merge happens, so types can be different
*/
- if A * 2 > B:
+ if A > B * 2:
double:string = "yes"
print A, "is more than twice", B, "?", double
else:
- double := A*2
- print "double", A, "is only", double
+ double := B*2
+ print "double", B, "is", double
a : number
a = A;
b:number = B
- if a > 0 and b > 0:
+ if a > 0 and then b > 0:
while a != b:
if a < b:
b = b - a
print "Yay, I found", target
case GiveUp:
print "Closest I found was", mid
+
+ size::=55
+ list:[size]number
+ list[0] = 1234
+ for i:=1; then i = i + 1; while i < size:
+ n := list[i-1] * list[i-1]
+ list[i] = (n / 100) % 10000
+
+ print "Before sort:"
+ for i:=0; then i = i + 1; while i < size:
+ print "list[",i,"]=",list[i]
+
+ for i := 1; then i=i+1; while i < size:
+ for j:=i-1; then j=j-1; while j >= 0:
+ if list[j] > list[j+1]:
+ t:= list[j]
+ list[j] = list[j+1]
+ list[j+1] = t
+ print "After sort:"
+ for i:=0; then i = i + 1; while i < size:
+ print "list[",i,"]=",list[i]
code / ocean / blobdiff