Variables जोड़ना

#include <ctype.h>
#include <string.h>

typedef struct { TokKind kind; int value; char name[32]; } Token;

static Token lex_ident(void) {
  Token t; t.kind = TOK_IDENT; int i = 0;
  while (isalnum((unsigned char)peek()) || peek() == '_')
    if (i < 31) t.name[i++] = advance(); else advance();
  t.name[i] = '\0';
  return t;
}

typedef struct Node {
  enum { N_NUM, N_BINOP, N_VAR, N_ASSIGN } kind;
  int value; char op; char name[32];
  struct Node *left, *right;  /* assign uses right as value expr */
} Node;

#define MAX_VARS 64

typedef struct {
  char names[MAX_VARS][32];
  int  values[MAX_VARS];
  int  count;
} Env;

static Env env;  /* global for this tiny example */

#include <string.h>

static int env_set(const char *name, int v) {
  for (int i = 0; i < env.count; i++)
    if (strcmp(env.names[i], name) == 0) {
      env.values[i] = v; return v;
    }
  strcpy(env.names[env.count], name);
  env.values[env.count] = v;
  env.count++;
  return v;
}

#include <stdio.h>
#include <stdlib.h>

static int env_get(const char *name) {
  for (int i = 0; i < env.count; i++)
    if (strcmp(env.names[i], name) == 0)
      return env.values[i];
  fprintf(stderr, "undefined variable: %s\n", name);
  exit(1);
}

static Node *parse_assign(void) {
  if (cur().kind == TOK_IDENT) {
    char saved[32]; strcpy(saved, cur().name);
    bump();
    if (cur().kind == TOK_ASSIGN) {
      bump();
      Node *val = parse_assign();
      return assign_node(saved, val);
    }
    return var_node(saved);  /* not an assignment */
  }
  return parse_expr();
}

int eval(Node *n) {
  switch (n->kind) {
    case N_NUM:    return n->value;
    case N_VAR:    return env_get(n->name);
    case N_ASSIGN: return env_set(n->name, eval(n->right));
    case N_BINOP: {
      int l = eval(n->left), r = eval(n->right);
      switch (n->op) {
        case '+': return l + r; case '-': return l - r;
        case '*': return l * r; case '/': return l / r;
      }
    }
  }
  return 0;
}

#include <stdio.h>
#include <string.h>

#define MAX_VARS 64
static char names[MAX_VARS][32];
static int  values[MAX_VARS];
static int  count;

static int env_set(const char *n,int v){
  for(int i=0;i<count;i++) if(!strcmp(names[i],n)){values[i]=v;return v;}
  strcpy(names[count],n); values[count]=v; count++; return v;
}
static int env_get(const char *n){
  for(int i=0;i<count;i++) if(!strcmp(names[i],n)) return values[i];
  return 0;
}

int main(void){
  env_set("x", 5);            /* x = 5 */
  int r = env_get("x") + 1;   /* x + 1 */
  printf("x = %d\n", env_get("x"));
  printf("x + 1 = %d\n", r);
  return 0;
}

typedef struct Env {
  char names[MAX_VARS][32];
  int  values[MAX_VARS];
  int  count;
  struct Env *parent;  /* enclosing scope */
} Env;