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evalexpr: parse: clean-up using new enum 

Instead of using characters for the different precedence related
functions, use the actual operator value.
This commit is contained in:
Bruno BELANYI 2020-10-30 19:33:35 +01:00
parent f7c8413e3c
commit 44bf3d98af
1 changed files with 36 additions and 32 deletions
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68
src/parse/climbing_parse.c
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@ -12,7 +12,7 @@
static const struct {
const char *op;
const int kind; // Because we store different kinds of enum...
const enum op_kind kind;
const int prio;
const enum { ASSOC_LEFT, ASSOC_RIGHT, ASSOC_NONE } assoc;
const enum { OP_INFIX, OP_PREFIX, OP_POSTFIX } fix;
@ -46,6 +46,7 @@ static enum op_kind char_to_binop(char c)
UNREACHABLE();
}
// Only works because no overlap between prefix and postfix operators
static enum op_kind char_to_unop(char c)
{
for (size_t i = 0; i < ARR_SIZE(ops); ++i)
@ -82,21 +83,19 @@ static bool is_postfix(char c)
return false;
}
static bool prec_between(char c, int min, int max)
static bool prec_between(enum op_kind op, int min, int max)
{
for (size_t i = 0; i < ARR_SIZE(ops); ++i)
if (c == ops[i].op[0] && ops[i].fix != OP_PREFIX)
if (op == ops[i].kind)
return min <= ops[i].prio && ops[i].prio <= max;
return false;
}
// This function happen to work the way the code is setup, because of operator
// ordering
static int right_prec(char c)
static int right_prec(enum op_kind op)
{
for (size_t i = 0; i < ARR_SIZE(ops); ++i)
if (c == ops[i].op[0])
if (op == ops[i].kind)
{
if (ops[i].assoc == ASSOC_RIGHT)
return ops[i].prio;
@ -106,12 +105,10 @@ static int right_prec(char c)
return INT_MIN;
}
// This function happen to work the way the code is setup, because of operator
// ordering
static int next_prec(char c)
static int next_prec(enum op_kind op)
{
for (size_t i = 0; i < ARR_SIZE(ops); ++i)
if (c == ops[i].op[0])
if (op == ops[i].kind)
{
if (ops[i].assoc != ASSOC_LEFT)
return ops[i].prio - 1;
@ -150,22 +147,42 @@ struct ast_node *climbing_parse(const char *input)
return ast;
}
static bool update_op(enum op_kind *op, const char **input)
{
skip_whitespace(input);
char c = *input[0];
if (is_binop(c))
{
*op = char_to_binop(c);
return true;
}
if (is_postfix(c))
{
*op = char_to_unop(c);
return true;
}
return false;
}
static struct ast_node *climbing_parse_internal(const char **input, int prec)
{
prec = prec;
struct ast_node *ast = parse_operand(input);
int r = INT_MAX;
while ((skip_whitespace(input), true) && // We need to skip the whitespace
(is_binop(*input[0]) || is_postfix(*input[0]))
&& prec_between(*input[0], prec, r) && ast)
enum op_kind op; // Used in the next loop
while (update_op(&op, input) // Initialise the operator
&& prec_between(op, prec, r) // Use newly initialized operator
&& ast)
{
const char c = *input[0];
eat_char(input);
if (is_binop(c))
{
enum op_kind op = char_to_binop(c);
struct ast_node *rhs = climbing_parse_internal(input, right_prec(c));
struct ast_node *rhs =
climbing_parse_internal(input, right_prec(op));
if (!rhs)
{
destroy_ast(ast);
@ -179,12 +196,12 @@ static struct ast_node *climbing_parse_internal(const char **input, int prec)
}
else
{
struct ast_node *tree = make_unop(char_to_unop(c), ast);
struct ast_node *tree = make_unop(op, ast);
if (!tree)
destroy_ast(ast); // Error case
ast = tree;
}
r = next_prec(c);
r = next_prec(op);
}
return ast;
@ -206,19 +223,6 @@ static bool my_atoi(const char **input, int *val)
return true;
}
static int next_prec_prefix(int op)
{
for (size_t i = 0; i < ARR_SIZE(ops); ++i)
if (ops[i].fix == OP_PREFIX && op == ops[i].kind)
{
if (ops[i].assoc != ASSOC_LEFT)
return ops[i].prio - 1;
return ops[i].prio;
}
return INT_MIN;
}
static struct ast_node *parse_operand(const char **input)
{
skip_whitespace(input); // Whitespace is not significant
@ -231,7 +235,7 @@ static struct ast_node *parse_operand(const char **input)
// Remove the parenthesis
eat_char(input);
ast = climbing_parse_internal(input, next_prec_prefix(op));
ast = climbing_parse_internal(input, next_prec(op));
if (!ast)
return NULL;