function terminal = identerm(str)% Identify `terminal symbols` to be parsed by the ACTL parser.%% Syntax:%   "terminal = identerm(str)"%% Description:%   Indentify the `terminal symbols` for the ACTL `grammar` in the input%   string "str" and create the ouput cell array "terminal" of the%   terminal symbols. There are 3 types of terminal symbols in our%   implementation of the ACTL grammar%%   * `single characters`: "'~'","'&'","'|'","'('","')'","'X'","'F'",%     "'G'","'U'","'R'","'A'"%%   * `equal sign`: "'=='"%%   * `name`: a string starting with a LOWERCASE alphabet followed by%     LOWERCASE alphabets, numbers ("'1'", ..., "'9'"), or underscores%     ('"_"').%%   Each terminal symbol in the output cell array is a structure with the%   following fields%%   * "symbol", one of the single character symbols, "'=='", or "'name'".%%   * "production", the `production` in the ACTL grammar to be applied (see%     help on function "parse.m"). This field is set to "'none'" for all%     terminal symbols.%%   * "value". For `single charater` and `equal sign` symbols, this field%     has the same value as the field "symbol". For the `name` symbols,%     this field contains actual the name string for the symbol.%% See Also:%   parse,compile_ap,build_ap,evaluate,model_checkSPECIAL_CHARACTERS = {'~','&','|','(',')','X','F','G','U','R','A'};% Implement the terminal identifier as a state machine.SINGLE_CHARACTER  = 0;NAME_ENTER        = 1;NAME_DURING       = 2;EQUAL_ENTER       = 4;EQUAL_EXIT        = 5;state = SINGLE_CHARACTER;idx = 1;terminal = {};while (idx <= length(str))    ch = str(idx);    % parser state transition    switch state        case {SINGLE_CHARACTER,EQUAL_EXIT}            if islowercase(ch)                state = NAME_ENTER;            elseif ch == '=';                state = EQUAL_ENTER;            elseif ~(isspace(ch) || ismember(ch,SPECIAL_CHARACTERS))                error([error_header(str,idx) 'Invalid character.'])            else                state = SINGLE_CHARACTER;            end        case {NAME_ENTER,NAME_DURING}            if ismember(ch,SPECIAL_CHARACTERS) || isspace(ch)                state = SINGLE_CHARACTER;            elseif ch == '=';                state = EQUAL_ENTER;            elseif islowercase(ch) || isnumber(ch) || (ch == '_')                state = NAME_DURING;            else                error([error_header(str,idx) ...                    'Invalid identifier name.']);            end        case EQUAL_ENTER            if (ch == '=')                state = EQUAL_EXIT;            else                error([error_header(str,idx) '= must be followed by another =.']);            end        otherwise            error('Unknown parse state.')    end        switch state        case SINGLE_CHARACTER            if ~isspace(ch)                terminal{end+1} = create_terminal(ch,ch); %#ok            end        case NAME_ENTER            terminal{end+1} = create_terminal('name',ch); %#ok        case NAME_DURING            terminal{end}.value = [terminal{end}.value ch]; %#ok        case EQUAL_EXIT            terminal{end+1} = create_terminal('==','=='); %#ok    end    idx = idx + 1;endif state == EQUAL_ENTER    error([error_header(str,idx-1) ...        'Unfinished ''==''.']);end% -----------------------------------------------------------------------------function terminal = create_terminal(symbol,value)% This routine creates a terminal symbol nodeterminal.symbol = symbol;terminal.production = 'none';terminal.value = value;% -----------------------------------------------------------------------------function st = islowercase(ch)st = ('a' <= ch) & (ch <= 'z');% -----------------------------------------------------------------------------function st = isnumber(ch)st = ('0' <= ch) & (ch <= '9');% -----------------------------------------------------------------------------function header = error_header(str,idx)l1 = sprintf('%s...\n',str(1:idx));l2 = sprintf('%s|\n',blanks(idx-1));header = [l1 l2];