Making Decisions: Choose Your Own Adventure

Lesson 4 — If/else, conditions, and a BBS trivia game that keeps score

Lesson 4 of Learning MEX

What you’ll build: A three-question BBS trivia game that checks answers, keeps score, and responds differently depending on how the caller does.

2:51 AM

Every script you’ve written so far runs in a straight line. Top to bottom. Same path, same output, same experience for everyone. The greeter greets. The profile card profiles. Nobody’s making any choices.

But every interesting thing that’s ever happened on a BBS involved a choice. Press Y to continue. Pick a door. Answer the question. Challenge your fate.

This lesson is about the fork in the road — the if statement and its friends. By the end, you’ll have a trivia game that asks questions, checks answers, keeps score, and gives the caller a different sign-off depending on how they did. Same script, different experience every time.

That’s when scripting stops being output and starts being interactive.

The if Statement

You’ve already used if a few times — checking for empty strings, testing usr.times. Here’s the full picture.

Basic Form

if (condition)
  statement;

If the condition is true (non-zero), the statement runs. If not, it’s skipped. Simple.

if / else

if (condition)
  statement1;
else
  statement2;

One path or the other. Never both. Never neither.

Compound Statements

When you need more than one line in a branch, wrap them in braces:

if (score >= 3)
{
  print("|10Perfect score!\n");
  print("|10You clearly know your stuff.\n");
}
else
{
  print("|14Not bad. Room to grow.\n");
}

Without the braces, only the first statement after if is conditional. Everything after it runs unconditionally. This is the most common beginner bug in any C-like language, and MEX is no exception.

else if Chains

MEX doesn’t have a switch statement. When you need multiple branches, chain else if:

if (score = 3)
  print("Perfect!");
else if (score = 2)
  print("Pretty good.");
else if (score = 1)
  print("Could be worse.");
else
  print("Ooof.");

It’s not as elegant as a switch, but it reads clearly and it works.

Comparison Operators

Here’s what you have to work with:

Operator	Meaning	Example
`=`	Equal to	`if (x = 5)`
`<>`	Not equal to	`if (x <> 5)`
`<`	Less than	`if (x < 10)`
`>`	Greater than	`if (x > 0)`
`<=`	Less than or equal	`if (x <= 100)`
`>=`	Greater than or equal	`if (x >= 1)`

And the logical operators to combine conditions:

Operator	Meaning	Example
`and`	Both must be true	`if (x > 0 and x < 10)`
`or`	Either can be true	`if (x = 1 or x = 2)`

Remember: = is comparison, := is assignment. Every other language on earth uses == for comparison. MEX doesn’t. You will get this wrong at least once. Probably at 3 AM. Probably tonight.

The Case Problem

String comparison in MEX is case-sensitive. The string "Maximus" is not equal to "maximus" or "MAXIMUS". They’re three different strings as far as the = operator is concerned.

For a trivia game, that’s a problem. You don’t want to mark someone wrong because they typed “fidonet” instead of “FidoNet.”

The fix: strupper() or strlower(). These built-in functions return a new string with all letters converted to uppercase or lowercase:

string: answer;
input_str(answer, INPUT_NLB_LINE, 0, 40, "|11> |15");

if (strupper(answer) = "MAXIMUS")
  print("Correct!\n");

Now it doesn’t matter whether they typed “Maximus”, “maximus”, “MAXIMUS”, or “mAxImUs”. strupper() normalizes everything to uppercase before the comparison. Problem solved.

The Trivia Game

Here’s the whole thing. Call it trivia.mex:

#include <max.mh>

int main()
{
  string: answer;
  int: score;

  score := 0;

  print("\n|11═══════════════════════════════════════\n");
  print("|14  BBS Trivia: How Well Do You Know\n");
  print("|14  Your History, |15", usr.name, "|14?\n");
  print("|11═══════════════════════════════════════|07\n\n");
  print("|03Three questions. No lifelines. Let's go.\n\n");

  // Question 1
  print("|14Q1: |07What BBS software shares its name with\n");
  print("    a Roman general? (Hint: you're using it.)\n");
  input_str(answer, INPUT_NLB_LINE, 0, 40, "|11> |15");

  if (strupper(answer) = "MAXIMUS")
  {
    print("|10Correct!|07 You're on it right now.\n\n");
    score := score + 1;
  }
  else
    print("|12Nope.|07 It's Maximus. You're literally using it.\n\n");

  // Question 2
  print("|14Q2: |07What network connected BBSes worldwide\n");
  print("    using store-and-forward message routing?\n");
  input_str(answer, INPUT_NLB_LINE, 0, 40, "|11> |15");

  if (strupper(answer) = "FIDONET" or strupper(answer) = "FIDO NET"
      or strupper(answer) = "FIDO")
  {
    print("|10Correct!|07 FidoNet — the original social network.\n\n");
    score := score + 1;
  }
  else
    print("|12Nope.|07 FidoNet. Est. 1984. Still running.\n\n");

  // Question 3
  print("|14Q3: |07What does BBS stand for?\n");
  input_str(answer, INPUT_NLB_LINE, 0, 60, "|11> |15");

  if (strfind(strupper(answer), "BULLETIN") <> -1
      and strfind(strupper(answer), "BOARD") <> -1
      and strfind(strupper(answer), "SYSTEM") <> -1)
  {
    print("|10Correct!|07 Bulletin Board System.\n\n");
    score := score + 1;
  }
  else
    print("|12Nope.|07 Bulletin Board System.\n\n");

  // Results
  print("|11═══════════════════════════════════════\n");
  print("|14  Score: |15", score, "|14 out of 3\n");
  print("|11═══════════════════════════════════════|07\n\n");

  if (score = 3)
    print("|10Perfect score! |07You are a true sysop.\n");
  else if (score = 2)
    print("|14Two out of three.|07 Respectable showing.\n");
  else if (score = 1)
    print("|06One out of three.|07 The spirit is willing.\n");
  else
    print("|12Zero.|07 ...are you sure you meant to call a BBS?\n");

  print("\n");
  return 0;
}

What’s New Here

Score tracking. score starts at 0 and gets incremented with score := score + 1 each time the caller answers correctly. It’s just an integer — nothing fancy. But it accumulates across the whole script, and the final if / else if chain uses it to pick a response.

strupper() for case-insensitive matching. Every answer gets uppercased before comparison. The caller can type in whatever case they want; we compare against an all-caps version of the expected answer.

or for multiple accepted answers. Question 2 accepts “FidoNet”, “Fido Net”, or just “Fido.” Each variation is its own comparison, connected with or. If any of them match, you get the point.

strfind() for partial matching. Question 3 is trickier — “Bulletin Board System” could be typed as “bulletin board system”, “A Bulletin Board System”, or “it’s a Bulletin Board System, obviously.” Instead of trying to match every possible phrasing, we use strfind() to check whether the answer contains each key word.

strfind() returns the position of the substring if found, or -1 if not. So strfind(str, "BULLETIN") <> -1 means “the word BULLETIN appears somewhere in this string.”

Compound conditions with and. The Question 3 check requires all three keywords to be present: BULLETIN and BOARD and SYSTEM. If the caller just types “bulletin” without the other words, they don’t get credit.

Compile and Run

mex trivia.mex

Test it yourself. Try correct answers, wrong answers, weird capitalization, partial matches. Press Enter without typing anything on a question and watch what happens. (It’ll count as wrong — the empty string doesn’t contain “BULLETIN”.)

Nesting

Conditions can go inside other conditions. You’ve actually seen this already in the else if chains, but here’s an explicit example:

if (usr.times > 10)
{
  if (usr.video = VIDEO_ANSI)
    print("|10Welcome back, veteran ANSI user!\n");
  else
    print("Welcome back, veteran caller!\n");
}
else
  print("Welcome, newcomer!\n");

The outer if checks call count. The inner if checks video mode. The result: regulars with ANSI get a colorful greeting, regulars without ANSI get a plain one, and newcomers get a different message entirely.

You can nest as deep as you want, but two or three levels is usually the practical limit before readability suffers. If your nesting starts looking like a staircase, consider breaking the inner logic into a helper function.

Boolean Values in MEX

MEX doesn’t have a dedicated true / false type. Instead:

Zero is false. Any integer, char, or long with value 0 is treated as false in a condition.
Non-zero is true. Anything else — 1, -1, 42, 'A' — is true.

max.mh defines TRUE as 1 and FALSE as 0 for readability, but they’re just integers. A condition like if (usr.hotkeys) works because usr.hotkeys is 1 when enabled and 0 when disabled — it’s already a boolean by convention.

What You Learned

if / else / else if — the core branching mechanism. One path runs, the others are skipped.
Comparison operators — =, <>, <, >, <=, >=. Remember: = is comparison, := is assignment.
Logical operators — and, or for combining conditions.
strupper() / strlower() — convert strings for case-insensitive comparison.
strfind() — search for a substring. Returns position or -1.
Score tracking — just an integer that accumulates. Simple and effective.
No switch statement — use else if chains instead.
Booleans — zero is false, non-zero is true.

Your scripts can make decisions now. But they still only do each thing once. The trivia game asks three questions — what if you wanted thirty? Copy-paste? No.

Next lesson: loops. Doing things more than once, without writing the same code more than once.

Lesson 5: “One More Time, With Feeling” →

Maximus BBS

Documentation for Maximus BBS — Next Generation