Function next_token

extern/tinyexpr/tinyexpr.c:229–293

void next_token(state *s) {
    s->type = TOK_NULL;

    do {

        if (!*s->next){
            s->type = TOK_END;
            return;
        }

        /* Try reading a number. */
        if ((s->next[0] >= '0' && s->next[0] <= '9') || s->next[0] == '.') {
            s->value = strtod(s->next, (char**)&s->next);
            s->type = TOK_NUMBER;
        } else {
            /* Look for a variable or builtin function call. */
            if (s->next[0] >= 'a' && s->next[0] <= 'z') {
                const char *start;
                start = s->next;
                while ((s->next[0] >= 'a' && s->next[0] <= 'z') || (s->next[0] >= '0' && s->next[0] <= '9') || (s->next[0] == '_')) s->next++;

                const te_variable *var = find_lookup(s, start, s->next - start);
                if (!var) var = find_builtin(start, s->next - start);

                if (!var) {
                    s->type = TOK_ERROR;
                } else {
                    switch(TYPE_MASK(var->type))
                    {
                        case TE_VARIABLE:
                            s->type = TOK_VARIABLE;
                            s->bound = var->address;
                            break;

                        case TE_CLOSURE0: case TE_CLOSURE1: case TE_CLOSURE2: case TE_CLOSURE3:         /* Falls through. */
                        case TE_CLOSURE4: case TE_CLOSURE5: case TE_CLOSURE6: case TE_CLOSURE7:         /* Falls through. */
                            s->context = var->context;                                                  /* Falls through. */

                        case TE_FUNCTION0: case TE_FUNCTION1: case TE_FUNCTION2: case TE_FUNCTION3:     /* Falls through. */
                        case TE_FUNCTION4: case TE_FUNCTION5: case TE_FUNCTION6: case TE_FUNCTION7:     /* Falls through. */
                            s->type = var->type;
                            s->function = var->address;
                            break;
                    }
                }

            } else {
                /* Look for an operator or special character. */
                switch (s->next++[0]) {
                    case '+': s->type = TOK_INFIX; s->function = add; break;
                    case '-': s->type = TOK_INFIX; s->function = sub; break;
                    case '*': s->type = TOK_INFIX; s->function = mul; break;
                    case '/': s->type = TOK_INFIX; s->function = divide; break;
                    case '^': s->type = TOK_INFIX; s->function = pow; break;
                    case '%': s->type = TOK_INFIX; s->function = fmod; break;
                    case '(': s->type = TOK_OPEN; break;
                    case ')': s->type = TOK_CLOSE; break;
                    case ',': s->type = TOK_SEP; break;