Step by Step solution about How to resolve the algorithm Amb step by step in the C programming language

This C code defines a function amb that takes a variable number of arguments, represented by a variable argument list (va_list). It acts as a way to try a series of choices until one succeeds or all fail. Here's a detailed breakdown of the code:

• amb Function:

  • It takes a size_t argument argc, which represents the number of choices to try, and a variable number of arguments of type const char * (string literals).
  • It allocates memory for an array of amb_t (string literals) named choices with a size equal to argc multiplied by the size of an amb_t.
  • It initializes a variable argument list ap and starts iterating through the arguments.
  • It populates the choices array with the amb_t arguments.
  • It tries each choice in the choices array using the TRY macro (not shown in the given code).
  • After trying all choices, it frees the allocated memory for the choices array.
  • If none of the choices succeed, it calls the FAIL macro (not shown in the given code).

• joins Function:

  • This function takes two const char * arguments, left and right, representing strings.
  • It checks if the last character of the left string is equal to the first character of the right string.
  • It returns 1 if they match and 0 if they don't.

• _main Function:

  • It defines four const char * variables: w1, w2, w3, and w4.
  • It calls the amb function to assign values to these variables. The amb function tries different choices for each variable and picks the first one that doesn't fail.
  • It checks if the last character of the current variable matches the first character of the next variable. If it doesn't, it calls amb again to try different choices.
  • Finally, it prints the values of w1, w2, w3, and w4 to the console.

When you run this program, it will generate a sentence by trying different combinations of words until it finds a valid sentence that satisfies the condition of having adjacent words with matching last and first characters.

This C code takes a variable number of strings and tries to combine them into a valid sentence. It uses a variadic function amb to choose one string from each group of options and verifies that the resulting sentence is grammatically correct by checking whether the last character of each word matches the first character of the next word. If the sentence is not grammatically correct, the program fails. Otherwise, it prints the sentence to the console.

Here's a detailed breakdown of the code:

1. Custom amb Function:

   • The amb function takes a variable number of string arguments and returns a randomly chosen string from among them.
   • It allocates memory to store the choices, populates the array with the arguments using va_arg, and tries each choice in a loop.
   • If none of the choices succeed, it calls FAIL to indicate failure.

2. String Joining Verification:

   • The joins function checks whether the last character of the left string matches the first character of the right string, indicating that they can be joined grammatically.

3. Main Function:

   • The _main function defines four string pointers w1, w2, w3, and w4.
   • It uses amb to randomly choose a string from each group of options:
     • w1 from "the", "that", "a"
     • w2 from "frog", "elephant", "thing"
     • w3 from "walked", "treaded", "grows"
     • w4 from "slowly", "quickly"
   • It then checks if the sentence is grammatically correct by verifying that each word can be joined to the next:
     • If w1 and w2 cannot be joined, it calls amb(0) to indicate a failure.
     • It repeats the process for w2 and w3, and w3 and w4.
   • If all the words can be joined grammatically, it prints the sentence to the console.

typedef const char * amb_t;

amb_t amb(size_t argc, ...)
{
  amb_t *choices;
  va_list ap;
  int i;
  
  if(argc) {
    choices = malloc(argc*sizeof(amb_t));
    va_start(ap, argc);
    i = 0;
    do { choices[i] = va_arg(ap, amb_t); } while(++i < argc);
    va_end(ap);
    
    i = 0;
    do { TRY(choices[i]); } while(++i < argc);
    free(choices);
  }
  
  FAIL;
}

int joins(const char *left, const char *right) { return left[strlen(left)-1] == right[0]; }

int _main() {
  const char *w1,*w2,*w3,*w4;
  
  w1 = amb(3, "the", "that", "a");
  w2 = amb(3, "frog", "elephant", "thing");
  w3 = amb(3, "walked", "treaded", "grows");
  w4 = amb(2, "slowly", "quickly");
  
  if(!joins(w1, w2)) amb(0);
  if(!joins(w2, w3)) amb(0);
  if(!joins(w3, w4)) amb(0);
  
  printf("%s %s %s %s\n", w1, w2, w3, w4);
  
  return EXIT_SUCCESS;
}