MBCDN

Dies ist eine alte Version des Dokuments!

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// erlaubte Zeichen für Mini-BASIC
static int is_allowed_basic_char(char c) {
    if (c == ' ' || c == '.' || c == '"' || c == '=' || c == '+' || c == '-' ||
        c == '*' || c == '/' || c == '(' || c == ')' || c == '<' || c == '>' ||
        c == ',' ) return 1;

    if (c >= 'A' && c <= 'Z') return 1;
    if (c >= '0' && c <= '9') return 1;
    return 0;
}

// ===================== MINI BASIC (int-only) =====================

#define BASIC_MAX_LINES 64
#define BASIC_LINE_LEN  96

typedef struct {
    uint16 line_no;
    uint8  used;
    char   text[BASIC_LINE_LEN];
} BasicLine;

static BasicLine g_prog[BASIC_MAX_LINES];
static int g_vars[26]; // A..Z

static void basic_reset_program(void) {
    for (int i = 0; i < BASIC_MAX_LINES; i++) {
        g_prog[i].used = 0;
        g_prog[i].line_no = 0;
        g_prog[i].text[0] = 0;
    }
}

static void basic_reset_vars(void) {
    for (int i = 0; i < 26; i++) g_vars[i] = 0;
}

static int is_space(char c) { return c == ' ' || c == '\t'; }

static char up(char c) {
    if (c >= 'a' && c <= 'z') return (char)(c - 'a' + 'A');
    return c;
}

static void skip_spaces(const char **p) {
    while (**p && is_space(**p)) (*p)++;
}

static int is_digit(char c) { return (c >= '0' && c <= '9'); }
static int is_alpha(char c) { return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'); }

static int starts_with_kw(const char *s, const char *kw) {
    // case-insensitive, kw muss "Wortgrenze" haben (Ende oder Space)
    int i = 0;
    while (kw[i]) {
        if (up(s[i]) != kw[i]) return 0;
        i++;
    }
    char next = s[i];
    return (next == 0 || is_space(next));
}

static uint16 parse_u16(const char **p) {
    skip_spaces(p);
    uint16 v = 0;
    while (is_digit(**p)) {
        v = (uint16)(v * 10 + (**p - '0'));
        (*p)++;
    }
    return v;
}

static int parse_int(const char **p) {
    skip_spaces(p);
    int sign = 1;
    if (**p == '+') { (*p)++; }
    else if (**p == '-') { sign = -1; (*p)++; }

    int v = 0;
    while (is_digit(**p)) {
        v = v * 10 + (**p - '0');
        (*p)++;
    }
    return v * sign;
}

static int find_line_index(uint16 line_no) {
    for (int i = 0; i < BASIC_MAX_LINES; i++) {
        if (g_prog[i].used && g_prog[i].line_no == line_no) return i;
    }
    return -1;
}

static int find_free_slot(void) {
    for (int i = 0; i < BASIC_MAX_LINES; i++) {
        if (!g_prog[i].used) return i;
    }
    return -1;
}

static int find_next_line_sorted(uint16 last_line, uint16 *out_line, int *out_idx) {
    int found = 0;
    uint16 best = 0xFFFF;
    int best_i = -1;

    for (int i = 0; i < BASIC_MAX_LINES; i++) {
        if (!g_prog[i].used) continue;
        uint16 ln = g_prog[i].line_no;
        if (ln > last_line && ln < best) {
            best = ln;
            best_i = i;
            found = 1;
        }
    }

    if (!found) return 0;
    *out_line = best;
    *out_idx = best_i;
    return 1;
}

static void basic_store_line(uint16 line_no, const char *rest) {
    // rest: nach der Zeilennummer (inkl. leading spaces)
    // Wenn rest leer -> löschen
    const char *p = rest;
    skip_spaces(&p);

    int idx = find_line_index(line_no);

    if (*p == 0) {
        if (idx >= 0) g_prog[idx].used = 0;
        return;
    }

    if (idx < 0) {
        idx = find_free_slot();
        if (idx < 0) {
            print_new_line();
            print_string("BASIC: OUT OF PROGRAM SPACE");
            return;
        }
        g_prog[idx].used = 1;
        g_prog[idx].line_no = line_no;
    }

    // copy text, uppercase keywords funktionieren trotzdem case-insensitive
    int j = 0;
    while (*p && j < BASIC_LINE_LEN - 1) {
        g_prog[idx].text[j++] = *p++;
    }
    g_prog[idx].text[j] = 0;
}

static void basic_list(void) {
    uint16 last = 0;
    uint16 ln;
    int idx;

    while (find_next_line_sorted(last, &ln, &idx)) {
        print_new_line();
        print_int((int)ln);
        print_string(" ");
        print_string(g_prog[idx].text);
        last = ln;
    }
}

static void basic_error(const char *msg) {
    print_new_line();
    print_string("BASIC ERROR: ");
    print_string((char*)msg);
}

// ---------- Expression parser (recursive descent) ----------
static int parse_expr(const char **p); // forward

static int parse_factor(const char **p) {
    skip_spaces(p);

    // unary
    if (**p == '+') { (*p)++; return parse_factor(p); }
    if (**p == '-') { (*p)++; return -parse_factor(p); }

    if (**p == '(') {
        (*p)++;
        int v = parse_expr(p);
        skip_spaces(p);
        if (**p == ')') (*p)++;
        else basic_error("MISSING )");
        return v;
    }

    // variable
    if (is_alpha(**p)) {
        char c = up(**p);
        (*p)++;
        if (c >= 'A' && c <= 'Z') return g_vars[c - 'A'];
        return 0;
    }

    // number
    if (is_digit(**p)) {
        return parse_int(p);
    }

    basic_error("BAD FACTOR");
    return 0;
}

static int parse_term(const char **p) {
    int v = parse_factor(p);
    for (;;) {
        skip_spaces(p);
        if (**p == '*') { (*p)++; v = v * parse_factor(p); }
        else if (**p == '/') {
            (*p)++;
            int d = parse_factor(p);
            if (d == 0) { basic_error("DIV BY ZERO"); return 0; }
            v = v / d;
        } else break;
    }
    return v;
}

static int parse_expr(const char **p) {
    int v = parse_term(p);
    for (;;) {
        skip_spaces(p);
        if (**p == '+') { (*p)++; v = v + parse_term(p); }
        else if (**p == '-') { (*p)++; v = v - parse_term(p); }
        else break;
    }
    return v;
}

static int parse_relop(const char **p, const char **out_op) {
    skip_spaces(p);
    // supported: =, <, >, <=, >=, <>
    if (**p == '=') { *out_op = "="; (*p)++; return 1; }
    if (**p == '<') {
        (*p)++;
        if (**p == '=') { *out_op = "<="; (*p)++; return 1; }
        if (**p == '>') { *out_op = "<>"; (*p)++; return 1; }
        *out_op = "<"; return 1;
    }
    if (**p == '>') {
        (*p)++;
        if (**p == '=') { *out_op = ">="; (*p)++; return 1; }
        *out_op = ">"; return 1;
    }
    return 0;
}

static int eval_relation(int a, int b, const char *op) {
    if (op[0] == '=' && op[1] == 0) return a == b;
    if (op[0] == '<' && op[1] == 0) return a < b;
    if (op[0] == '>' && op[1] == 0) return a > b;
    if (op[0] == '<' && op[1] == '=') return a <= b;
    if (op[0] == '>' && op[1] == '=') return a >= b;
    if (op[0] == '<' && op[1] == '>') return a != b;
    return 0;
}

// ---------- Statement execution ----------
static int basic_exec_stmt(const char *line, uint16 *pc_line /*in/out*/, int *stop /*out*/) {
    const char *p = line;
    skip_spaces(&p);

    if (*p == 0) return 1;

    // REM
    if (starts_with_kw(p, "REM")) return 1;

    // END
    if (starts_with_kw(p, "END")) { *stop = 1; return 1; }

    // PRINT
    if (starts_with_kw(p, "PRINT")) {
        p += 5;
        skip_spaces(&p);

        // PRINT "TEXT"
        if (*p == '"') {
            p++;
            print_new_line();
            while (*p && *p != '"') {
                print_char(*p++);
            }
            if (*p == '"') p++;
            return 1;
        }

        // PRINT expr
        int v = parse_expr(&p);
        print_new_line();
        print_int(v);
        return 1;
    }

    // LET (optional)
    if (starts_with_kw(p, "LET")) {
        p += 3;
        skip_spaces(&p);
    }

    // IF expr rel expr THEN line
    if (starts_with_kw(p, "IF")) {
        p += 2;
        int left = parse_expr(&p);

        const char *op = 0;
        if (!parse_relop(&p, &op)) { basic_error("IF NEEDS RELOP"); return 0; }

        int right = parse_expr(&p);

        skip_spaces(&p);
        if (!starts_with_kw(p, "THEN")) { basic_error("IF NEEDS THEN"); return 0; }
        p += 4;

        uint16 target = parse_u16(&p);
        if (target == 0) { basic_error("BAD THEN LINE"); return 0; }

        if (eval_relation(left, right, op)) {
            *pc_line = (uint16)(target - 1); // Trick: RUN loop nimmt "next > pc_line"
        }
        return 1;
    }

    // GOTO line
    if (starts_with_kw(p, "GOTO")) {
        p += 4;
        uint16 target = parse_u16(&p);
        if (target == 0) { basic_error("BAD GOTO LINE"); return 0; }
        *pc_line = (uint16)(target - 1);
        return 1;
    }

    // Assignment: A = expr
    if (is_alpha(*p)) {
        char vname = up(*p++);
        if (vname < 'A' || vname > 'Z') { basic_error("BAD VAR"); return 0; }
        skip_spaces(&p);
        if (*p != '=') { basic_error("EXPECTED ="); return 0; }
        p++;
        int value = parse_expr(&p);
        g_vars[vname - 'A'] = value;
        return 1;
    }

    basic_error("UNKNOWN STATEMENT");
    return 0;
}

static void basic_run(void) {
    uint16 pc = 0;         // last executed line_no (for sorted iteration)
    int stop = 0;

    // Start at "before" first line:
    pc = 0;

    while (!stop) {
        uint16 ln;
        int idx;
        if (!find_next_line_sorted(pc, &ln, &idx)) break;

        // execute
        uint16 pc_before = ln;
        uint16 pc_line = ln;
        basic_exec_stmt(g_prog[idx].text, &pc_line, &stop);

        // pc_line may be changed by GOTO/IF
        pc = pc_line;

        // normal case: move to next after current
        if (pc == pc_before) pc = ln;
    }
}

// ---------- REPL line handler ----------
static void basic_repl_line(const char *input) {
    const char *p = input;
    skip_spaces(&p);
    if (*p == 0) return;

    // line starts with number? -> program line
    if (is_digit(*p)) {
        uint16 ln = parse_u16(&p);
        basic_store_line(ln, p);
        return;
    }

    // Immediate commands
    if (starts_with_kw(p, "LIST")) { basic_list(); return; }
    if (starts_with_kw(p, "RUN"))  { basic_run(); return; }
    if (starts_with_kw(p, "NEW"))  { basic_reset_program(); basic_reset_vars(); print_new_line(); print_string("OK"); return; }

    // keep your old shell commands too:
    if (starts_with_kw(p, "HELP")) {
        print_new_line();
        print_string("Available commands:");
        print_new_line();
        print_string("  HELP   - Prints this help");
        print_new_line();
        print_string("  REBOOT - Reboot the system");
        print_new_line();
        print_string("  NEW    - Clear BASIC program + vars");
        print_new_line();
        print_string("  LIST   - List BASIC program");
        print_new_line();
        print_string("  RUN    - Run BASIC program");
        print_new_line();
        print_string("BASIC examples:");
        print_new_line();
        print_string("  10 A=1+2*3");
        print_new_line();
        print_string("  20 PRINT A");
        print_new_line();
        print_string("  30 IF A=7 THEN 50");
        print_new_line();
        print_string("  40 GOTO 20");
        print_new_line();
        print_string("  50 END");
        return;
    }

    if (starts_with_kw(p, "REBOOT")) { do_reboot(); return; }

    // Otherwise: treat as immediate BASIC statement (PRINT/LET/A=.../IF/GOTO/END)
    uint16 dummy = 0;
    int stop = 0;
    basic_exec_stmt(p, &dummy, &stop);
}

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