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redis/expr.c

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/* Filtering of objects based on simple expressions.
* This powers the FILTER option of Vector Sets, but it is otherwise
* general code to be used when we want to tell if a given object (with fields)
* passes or fails a given test for scalars, strings, ...
*
* Copyright(C) 2024-2025 Salvatore Sanfilippo. All Rights Reserved.
*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#include "cJSON.h"
#define EXPR_TOKEN_EOF 0
#define EXPR_TOKEN_NUM 1
#define EXPR_TOKEN_STR 2
#define EXPR_TOKEN_TUPLE 3
#define EXPR_TOKEN_SELECTOR 4
#define EXPR_TOKEN_OP 5
#define EXPR_OP_OPAREN 0 /* ( */
#define EXPR_OP_CPAREN 1 /* ) */
#define EXPR_OP_NOT 2 /* ! */
#define EXPR_OP_POW 3 /* ** */
#define EXPR_OP_MULT 4 /* * */
#define EXPR_OP_DIV 5 /* / */
#define EXPR_OP_MOD 6 /* % */
#define EXPR_OP_SUM 7 /* + */
#define EXPR_OP_DIFF 8 /* - */
#define EXPR_OP_GT 9 /* > */
#define EXPR_OP_GTE 10 /* >= */
#define EXPR_OP_LT 11 /* < */
#define EXPR_OP_LTE 12 /* <= */
#define EXPR_OP_EQ 13 /* == */
#define EXPR_OP_NEQ 14 /* != */
#define EXPR_OP_IN 15 /* in */
#define EXPR_OP_AND 16 /* and */
#define EXPR_OP_OR 17 /* or */
/* This structure represents a token in our expression. It's either
* literals like 4, "foo", or operators like "+", "-", "and", or
* json selectors, that start with a dot: ".age", ".properties.somearray[1]" */
typedef struct exprtoken {
int token_type; // Token type of the just parsed token.
int offset; // Chars offset in expression.
union {
double num; // Value for EXPR_TOKEN_NUM.
struct {
char *start; // String pointer for EXPR_TOKEN_STR / SELECTOR.
size_t len; // String len for EXPR_TOKEN_STR / SELECTOR.
} str;
int opcode; // Opcode ID for EXPR_TOKEN_OP.
struct {
struct exprtoken *ele;
size_t len;
} tuple; // Tuples are like [1, 2, 3] for "in" operator.
};
} exprtoken;
/* Simple stack of expr tokens. This is used both to represent the stack
* of values and the stack of operands during VM execution. */
typedef struct exprstack {
exprtoken **items;
int numitems;
int allocsize;
} exprstack;
typedef struct exprstate {
char *expr; /* Expression string to compile. Note that
* expression token strings point directly to this
* string. */
char *p; // Currnet position inside 'expr', while parsing.
exprtoken current; // Last token parsed.
int syntax_error; // True if a syntax error was found compiling.
// Virtual machine state.
exprstack values_stack;
exprstack ops_stack;
exprstack tokens; // Expression processed into a sequence of tokens.
exprstack program; // Expression compiled into opcodes and values.
} exprstate;
/* Valid operators. */
struct {
char *opname;
int oplen;
int opcode;
int precedence;
int arity;
} ExprOptable[] = {
{"(", 1, EXPR_OP_OPAREN, 7, 0},
{")", 1, EXPR_OP_CPAREN, 7, 0},
{"!", 1, EXPR_OP_NOT, 6, 1},
{"not", 3, EXPR_OP_NOT, 6, 1},
{"**", 2, EXPR_OP_POW, 5, 2},
{"*", 1, EXPR_OP_MULT, 4, 2},
{"/", 1, EXPR_OP_DIV, 4, 2},
{"%", 1, EXPR_OP_MOD, 4, 2},
{"+", 1, EXPR_OP_SUM, 3, 2},
{"-", 1, EXPR_OP_DIFF, 3, 2},
{">", 1, EXPR_OP_GT, 2, 2},
{">=", 2, EXPR_OP_GTE, 2, 2},
{"<", 1, EXPR_OP_LT, 2, 2},
{"<=", 2, EXPR_OP_LTE, 2, 2},
{"==", 2, EXPR_OP_EQ, 2, 2},
{"!=", 2, EXPR_OP_NEQ, 2, 2},
{"in", 2, EXPR_OP_IN, 2, 2},
{"and", 3, EXPR_OP_AND, 1, 2},
{"&& ", 2, EXPR_OP_AND, 1, 2},
{"or", 2, EXPR_OP_OR, 0, 2},
{"||", 2, EXPR_OP_OR, 0, 2},
{NULL, 0, 0, 0, 0} // Terminator.
};
#define EXPR_OP_SPECIALCHARS "+-*%/!()<>=|&"
/* ================================ Expr token ============================== */
void exprFreeToken(exprtoken *t) {
if (t == NULL) return;
free(t);
}
/* ============================== Stack handling ============================ */
#include <stdlib.h>
#include <string.h>
#define EXPR_STACK_INITIAL_SIZE 16
/* Initialize a new expression stack. */
void exprStackInit(exprstack *stack) {
stack->items = malloc(sizeof(exprtoken*) * EXPR_STACK_INITIAL_SIZE);
stack->numitems = 0;
stack->allocsize = EXPR_STACK_INITIAL_SIZE;
}
/* Push a token pointer onto the stack. Return 0 on out of memory
* (leaving the stack as it is), 1 on success. */
int exprStackPush(exprstack *stack, exprtoken *token) {
/* Check if we need to grow the stack. */
if (stack->numitems == stack->allocsize) {
size_t newsize = stack->allocsize * 2;
exprtoken **newitems =
realloc(stack->items, sizeof(exprtoken*) * newsize);
if (newitems == NULL) return 0;
stack->items = newitems;
stack->allocsize = newsize;
}
stack->items[stack->numitems] = token;
stack->numitems++;
return 1;
}
/* Pop a token pointer from the stack. Return NULL if the stack is
* empty. */
exprtoken *exprStackPop(exprstack *stack) {
if (stack->numitems == 0) return NULL;
stack->numitems--;
return stack->items[stack->numitems];
}
/* Just return the last element pushed, without consuming it. */
exprtoken *exprStackPeek(exprstack *stack) {
if (stack->numitems == 0) return NULL;
return stack->items[stack->numitems-1];
}
/* Free the stack structure state, including the items it contains, that are
* assumed to be heap allocated. The passed pointer itself is not freed. */
void exprStackFree(exprstack *stack) {
for (int j = 0; j < stack->numitems; j++)
exprFreeToken(stack->items[j]);
free(stack->items);
}
/* Just reset the stack removing all the items, but leaving it in a state
* that makes it still usable for new elements. */
void exprStackReset(exprstack *stack) {
for (int j = 0; j < stack->numitems; j++)
exprFreeToken(stack->items[j]);
stack->numitems = 0;
}
/* =========================== Expression compilation ======================= */
void exprConsumeSpaces(exprstate *es) {
while(es->p[0] && isspace(es->p[0])) es->p++;
}
void exprParseOperatorOrSelector(exprstate *es) {
char *start = es->p;
if (es->p[0] == '.') {
es->current.token_type = EXPR_TOKEN_SELECTOR;
es->p++;
} else {
es->current.token_type = EXPR_TOKEN_OP;
}
while(es->p[0] &&
(isalpha(es->p[0]) ||
strchr(EXPR_OP_SPECIALCHARS,es->p[0]) != NULL))
{
es->p++;
}
int matchlen = es->p - start;
/* If this is not a selector for an attribute to retrive, then
* it must be one of the valid operators. */
int bestlen = 0;
if (es->current.token_type == EXPR_TOKEN_OP) {
int j;
for (j = 0; ExprOptable[j].opname != NULL; j++) {
if (ExprOptable[j].oplen > matchlen) continue;
if (memcmp(ExprOptable[j].opname, start, ExprOptable[j].oplen) != 0)
{
continue;
}
if (ExprOptable[j].oplen > bestlen) {
es->current.opcode = ExprOptable[j].opcode;
bestlen = ExprOptable[j].oplen;
}
}
if (bestlen == 0) {
es->syntax_error++;
} else {
es->p = start + bestlen;
}
} else {
es->current.str.start = start;
es->current.str.len = matchlen;
}
}
void exprParseNumber(exprstate *es) {
es->current.token_type = EXPR_TOKEN_NUM;
char num[64];
int idx = 0;
while(isdigit(es->p[0]) || (idx == 0 && es->p[0] == '-')) {
if (idx == sizeof(num)-1) {
es->syntax_error++; // Number is too long.
break;
}
num[idx++] = es->p[0];
es->p++;
}
num[idx] = 0;
char *endptr;
es->current.num = strtod(num, &endptr);
if (*endptr != '\0') es->syntax_error++;
}
void exprParseString(exprstate *es) {
char quote = es->p[0]; /* Store the quote type (' or "). */
es->p++; /* Skip opening quote. */
es->current.token_type = EXPR_TOKEN_STR;
es->current.str.start = es->p;
while(es->p[0] != '\0') {
if (es->p[0] == '\\' && es->p[1] != '\0') {
es->p += 2; // Skip escaped char.
continue;
}
if (es->p[0] == quote) {
es->current.str.len =
es->p - es->current.str.start;
es->p++; // Skip closing quote.
return;
}
es->p++;
}
/* If we reach here, string was not terminated. */
es->syntax_error++;
}
/* Deallocate the object returned by exprCompile(). */
void exprFree(exprstate *es) {
if (es == NULL) return;
/* Free the original expression string. */
if (es->expr) free(es->expr);
/* Free all stacks. */
exprStackFree(&es->values_stack);
exprStackFree(&es->ops_stack);
exprStackFree(&es->tokens);
exprStackFree(&es->program);
/* Free the state object itself. */
free(es);
}
/* Split the provided expression into a stack of tokens. Returns
* 0 on success, 1 on error. */
int exprTokenize(exprstate *es, int *errpos) {
/* Main parsing loop. */
while(1) {
exprConsumeSpaces(es);
/* Set a flag to see if we can consider the - part of the
* number, or an operator. */
int minus_is_number = 0; // By default is an operator.
exprtoken *last = exprStackPeek(&es->tokens);
if (last == NULL) {
/* If we are at the start of an expression, the minus is
* considered a number. */
minus_is_number = 1;
} else if (last->token_type == EXPR_TOKEN_OP &&
last->opcode != EXPR_OP_CPAREN)
{
/* Also, if the previous token was an operator, the minus
* is considered a number, unless the previous operator is
* a closing parens. In such case it's like (...) -5, or alike
* and we want to emit an operator. */
minus_is_number = 1;
}
/* Parse based on the current character. */
if (*es->p == '\0') {
es->current.token_type = EXPR_TOKEN_EOF;
} else if (isdigit(*es->p) ||
(minus_is_number && *es->p == '-' && isdigit(es->p[1])))
{
exprParseNumber(es);
} else if (*es->p == '"' || *es->p == '\'') {
exprParseString(es);
} else if (*es->p == '.' || isalpha(*es->p) ||
strchr(EXPR_OP_SPECIALCHARS, *es->p)) {
exprParseOperatorOrSelector(es);
} else {
es->syntax_error++;
}
if (es->syntax_error) {
if (errpos) *errpos = es->p - es->expr;
return 1; // Syntax Error.
}
/* Allocate and copy current token to tokens stack */
exprtoken *token = malloc(sizeof(exprtoken));
if (!token) return 1; // OOM.
*token = es->current; /* Copy the entire structure. */
token->offset = es->p - es->expr; /* To report errors gracefully. */
if (!exprStackPush(&es->tokens, token)) {
exprFreeToken(token);
return 1; // OOM.
}
if (es->current.token_type == EXPR_TOKEN_EOF) break;
}
return 0;
}
/* Helper function to get operator precedence from the operator table. */
int exprGetOpPrecedence(int opcode) {
for (int i = 0; ExprOptable[i].opname != NULL; i++) {
if (ExprOptable[i].opcode == opcode)
return ExprOptable[i].precedence;
}
return -1;
}
/* Helper function to get operator arity from the operator table. */
int exprGetOpArity(int opcode) {
for (int i = 0; ExprOptable[i].opname != NULL; i++) {
if (ExprOptable[i].opcode == opcode)
return ExprOptable[i].arity;
}
return -1;
}
/* Process an operator during compilation. Returns 0 on success, 1 on error. */
int exprProcessOperator(exprstate *es, exprtoken *op, int *stack_items, int *errpos) {
if (op->opcode == EXPR_OP_OPAREN) {
// This is just a marker for us. Do nothing.
if (!exprStackPush(&es->ops_stack, op)) return 1;
return 0;
}
if (op->opcode == EXPR_OP_CPAREN) {
/* Process operators until we find the matching opening parenthesis. */
while (1) {
exprtoken *top_op = exprStackPop(&es->ops_stack);
if (top_op == NULL) {
if (errpos) *errpos = op->offset;
return 1;
}
if (top_op->opcode == EXPR_OP_OPAREN) {
exprFreeToken(top_op); // Free the opening parenthesis token.
exprFreeToken(op); // Free the closing parenthesis token.
return 0;
}
int arity = exprGetOpArity(top_op->opcode);
if (*stack_items < arity) {
if (errpos) *errpos = top_op->offset;
return 1;
}
if (!exprStackPush(&es->program, top_op)) return 1;
*stack_items = *stack_items - arity + 1;
}
}
int curr_prec = exprGetOpPrecedence(op->opcode);
/* Process operators with higher or equal precedence. */
while (1) {
exprtoken *top_op = exprStackPeek(&es->ops_stack);
if (top_op == NULL || top_op->opcode == EXPR_OP_OPAREN) break;
int top_prec = exprGetOpPrecedence(top_op->opcode);
if (top_prec < curr_prec) break;
/* Pop and add to program. */
top_op = exprStackPop(&es->ops_stack);
int arity = exprGetOpArity(top_op->opcode);
if (*stack_items < arity) {
if (errpos) *errpos = top_op->offset;
return 1;
}
if (!exprStackPush(&es->program, top_op)) return 1;
*stack_items = *stack_items - arity + 1;
}
/* Push current operator. */
if (!exprStackPush(&es->ops_stack, op)) return 1;
return 0;
}
/* Compile the expression into a set of push-value and exec-operator
* that exprRun() can execute. The function returns an expstate object
* that can be used for execution of the program. On error, NULL
* is returned, and optionally the position of the error into the
* expression is returned by reference. */
exprstate *exprCompile(char *expr, int *errpos) {
/* Initialize expression state. */
exprstate *es = malloc(sizeof(exprstate));
if (!es) return NULL;
es->expr = strdup(expr);
if (!es->expr) {
free(es);
return NULL;
}
es->p = es->expr;
es->syntax_error = 0;
/* Initialize all stacks. */
exprStackInit(&es->values_stack);
exprStackInit(&es->ops_stack);
exprStackInit(&es->tokens);
exprStackInit(&es->program);
/* Tokenization. */
if (exprTokenize(es, errpos)) {
exprFree(es);
return NULL;
}
/* Compile the expression into a sequence of operations. */
int stack_items = 0; // Track # of items that would be on the stack
// during execution. This way we can detect arity
// issues at compile time.
/* Process each token. */
for (int i = 0; i < es->tokens.numitems; i++) {
exprtoken *token = es->tokens.items[i];
if (token->token_type == EXPR_TOKEN_EOF) break;
/* Handle values (numbers, strings, selectors). */
if (token->token_type == EXPR_TOKEN_NUM ||
token->token_type == EXPR_TOKEN_STR ||
token->token_type == EXPR_TOKEN_SELECTOR)
{
exprtoken *value_token = malloc(sizeof(exprtoken));
if (!value_token) {
if (errpos) *errpos = token->offset;
exprFree(es);
return NULL;
}
*value_token = *token; // Copy the token.
if (!exprStackPush(&es->program, value_token)) {
exprFreeToken(value_token);
if (errpos) *errpos = token->offset;
exprFree(es);
return NULL;
}
stack_items++;
continue;
}
/* Handle operators. */
if (token->token_type == EXPR_TOKEN_OP) {
exprtoken *op_token = malloc(sizeof(exprtoken));
if (!op_token) {
if (errpos) *errpos = token->offset;
exprFree(es);
return NULL;
}
*op_token = *token; // Copy the token.
if (exprProcessOperator(es, op_token, &stack_items, errpos)) {
exprFree(es);
return NULL;
}
continue;
}
}
/* Process remaining operators on the stack. */
while (es->ops_stack.numitems > 0) {
exprtoken *op = exprStackPop(&es->ops_stack);
if (op->opcode == EXPR_OP_OPAREN) {
if (errpos) *errpos = op->offset;
exprFreeToken(op);
exprFree(es);
return NULL;
}
int arity = exprGetOpArity(op->opcode);
if (stack_items < arity) {
if (errpos) *errpos = op->offset;
exprFreeToken(op);
exprFree(es);
return NULL;
}
if (!exprStackPush(&es->program, op)) {
exprFreeToken(op);
if (errpos) *errpos = op->offset;
exprFree(es);
return NULL;
}
stack_items = stack_items - arity + 1;
}
/* Verify that exactly one value would remain on the stack after
* execution. We could also check that such value is a number, but this
* would make the code more complex without much gains. */
if (stack_items != 1) {
if (errpos) {
/* Point to the last token's offset for error reporting. */
exprtoken *last = es->tokens.items[es->tokens.numitems - 1];
*errpos = last->offset;
}
exprFree(es);
return NULL;
}
return es;
}
/* ============================ Expression execution ======================== */
/* Convert a token to its numeric value. For strings we attempt to parse them
* as numbers, returning 0 if conversion fails. */
double exprTokenToNum(exprtoken *t) {
char buf[128];
if (t->token_type == EXPR_TOKEN_NUM) {
return t->num;
} else if (t->token_type == EXPR_TOKEN_STR && t->str.len < sizeof(buf)) {
memcpy(buf, t->str.start, t->str.len);
buf[t->str.len] = '\0';
char *endptr;
double val = strtod(buf, &endptr);
return *endptr == '\0' ? val : 0;
} else {
return 0;
}
}
/* Conver obejct to true/false (0 or 1) */
double exprTokenToBool(exprtoken *t) {
if (t->token_type == EXPR_TOKEN_NUM) {
return t->num != 0;
} else if (t->token_type == EXPR_TOKEN_STR && t->str.len == 0) {
return 0; // Empty string are false, like in Javascript.
} else {
return 1; // Every non numerical type is true.
}
}
/* Compare two tokens. Returns true if they are equal. */
int exprTokensEqual(exprtoken *a, exprtoken *b) {
// If both are strings, do string comparison.
if (a->token_type == EXPR_TOKEN_STR && b->token_type == EXPR_TOKEN_STR) {
return a->str.len == b->str.len &&
memcmp(a->str.start, b->str.start, a->str.len) == 0;
}
// If both are numbers, do numeric comparison.
if (a->token_type == EXPR_TOKEN_NUM && b->token_type == EXPR_TOKEN_NUM) {
return a->num == b->num;
}
// Mixed types - convert to numbers and compare.
return exprTokenToNum(a) == exprTokenToNum(b);
}
/* Execute the compiled expression program. Returns 1 if the final stack value
* evaluates to true, 0 otherwise. Also returns 0 if any selector callback fails. */
int exprRun(exprstate *es, char *json, size_t json_len) {
exprStackReset(&es->values_stack);
cJSON *parsed_json = NULL;
// Execute each instruction in the program.
for (int i = 0; i < es->program.numitems; i++) {
exprtoken *t = es->program.items[i];
// Handle selectors by calling the callback.
if (t->token_type == EXPR_TOKEN_SELECTOR) {
exprtoken *result = malloc(sizeof(exprtoken));
if (result != NULL && json != NULL) {
if (parsed_json == NULL)
parsed_json = cJSON_ParseWithLength(json,json_len);
if (parsed_json) {
exprStackPush(&es->values_stack, result);
continue;
}
}
exprFreeToken(result);
if (parsed_json) cJSON_Delete(parsed_json);
return 0; // Selector not found or OOM: expression fails.
}
// Push non-operator values directly onto the stack.
if (t->token_type != EXPR_TOKEN_OP) {
exprtoken *nt = malloc(sizeof(exprtoken));
*nt = *t;
exprStackPush(&es->values_stack, nt);
continue;
}
// Handle operators.
exprtoken *result = malloc(sizeof(exprtoken));
result->token_type = EXPR_TOKEN_NUM;
// Pop operands - we know we have enough from compile-time checks.
exprtoken *b = exprStackPop(&es->values_stack);
exprtoken *a = NULL;
if (exprGetOpArity(t->opcode) == 2) {
a = exprStackPop(&es->values_stack);
}
switch(t->opcode) {
case EXPR_OP_NOT:
result->num = exprTokenToBool(b) == 0 ? 1 : 0;
break;
case EXPR_OP_POW: {
double base = exprTokenToNum(a);
double exp = exprTokenToNum(b);
result->num = pow(base, exp);
break;
}
case EXPR_OP_MULT:
result->num = exprTokenToNum(a) * exprTokenToNum(b);
break;
case EXPR_OP_DIV:
result->num = exprTokenToNum(a) / exprTokenToNum(b);
break;
case EXPR_OP_MOD: {
double va = exprTokenToNum(a);
double vb = exprTokenToNum(b);
result->num = fmod(va, vb);
break;
}
case EXPR_OP_SUM:
result->num = exprTokenToNum(a) + exprTokenToNum(b);
break;
case EXPR_OP_DIFF:
result->num = exprTokenToNum(a) - exprTokenToNum(b);
break;
case EXPR_OP_GT:
result->num = exprTokenToNum(a) > exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_GTE:
result->num = exprTokenToNum(a) >= exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_LT:
result->num = exprTokenToNum(a) < exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_LTE:
result->num = exprTokenToNum(a) <= exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_EQ:
result->num = exprTokensEqual(a, b) ? 1 : 0;
break;
case EXPR_OP_NEQ:
result->num = !exprTokensEqual(a, b) ? 1 : 0;
break;
case EXPR_OP_IN: {
// For 'in' operator, b must be a tuple.
result->num = 0; // Default to false.
if (b->token_type == EXPR_TOKEN_TUPLE) {
for (size_t j = 0; j < b->tuple.len; j++) {
if (exprTokensEqual(a, &b->tuple.ele[j])) {
result->num = 1; // Found a match.
break;
}
}
}
break;
}
case EXPR_OP_AND:
result->num =
exprTokenToBool(a) != 0 && exprTokenToBool(b) != 0 ? 1 : 0;
break;
case EXPR_OP_OR:
result->num =
exprTokenToBool(a) != 0 || exprTokenToBool(b) != 0 ? 1 : 0;
break;
default:
// Do nothing: we don't want runtime errors.
break;
}
// Free operands and push result.
if (a) exprFreeToken(a);
exprFreeToken(b);
exprStackPush(&es->values_stack, result);
}
if (parsed_json) cJSON_Delete(parsed_json);
// Get final result from stack.
exprtoken *final = exprStackPop(&es->values_stack);
if (final == NULL) return 0;
// Convert result to boolean.
int retval = exprTokenToBool(final);
exprFreeToken(final);
return retval;
}
/* ============================ Simple test main ============================ */
#ifdef TEST_MAIN
void exprPrintToken(exprtoken *t) {
switch(t->token_type) {
case EXPR_TOKEN_EOF:
printf("EOF");
break;
case EXPR_TOKEN_NUM:
printf("NUM:%g", t->num);
break;
case EXPR_TOKEN_STR:
printf("STR:\"%.*s\"", (int)t->str.len, t->str.start);
break;
case EXPR_TOKEN_SELECTOR:
printf("SEL:%.*s", (int)t->str.len, t->str.start);
break;
case EXPR_TOKEN_OP:
printf("OP:");
for (int i = 0; ExprOptable[i].opname != NULL; i++) {
if (ExprOptable[i].opcode == t->opcode) {
printf("%s", ExprOptable[i].opname);
break;
}
}
break;
default:
printf("UNKNOWN");
break;
}
}
void exprPrintStack(exprstack *stack, const char *name) {
printf("%s (%d items):", name, stack->numitems);
for (int j = 0; j < stack->numitems; j++) {
printf(" ");
exprPrintToken(stack->items[j]);
}
printf("\n");
}
int main(int argc, char **argv) {
char *testexpr = "(5+2)*3 and 'foo'";
char *testjson = "{\"year\": 1984, \"name\": \"The Matrix\"}";
if (argc >= 2) testexpr = argv[1];
if (argc >= 3) testjson = argv[2];
printf("Compiling expression: %s\n", testexpr);
int errpos = 0;
exprstate *es = exprCompile(testexpr,&errpos);
if (es == NULL) {
printf("Compilation failed near \"...%s\"\n", testexpr+errpos);
return 1;
}
exprPrintStack(&es->tokens, "Tokens");
exprPrintStack(&es->program, "Program");
printf("Running against object: %s\n", testjson);
int result = exprRun(es,testjson,strlen(testjson));
printf("Result: %s\n", result ? "True" : "False");
exprFree(es);
return 0;
}
#endif
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