OpenEuphoria

1. load_map in map.e - unstructured programming example.

• Posted by gimlet May 08, 2014
• 1477 views

Unfortunately this is a long post because I feel it is necessary to provide background as the code is quite obscure.

I have been reluctant to post because I could be seen as 'picking-on' Euphoria and posting the negative. However nothing is improved unless it is questioned.

So to begin

If you read the notes you may understand what the procedure is intended to do. But a precis:

Blank lines and comments are ignored. A key-value line is <key> = <value> where <key> and <value> are Eu objects. A line may be laid out over several lines if each line except the last ends with a continuation character ( `,${` ). Lines are evaluated applying get:value() to the key and value and placed into a map.

load_map is a potentially valuable procedure. It is a pity it is all but unusable.

load_map and save_map have been mentioned several times as having problems but the code has not been corrected (a major task?) or removed.

-- 
-- Example 1: 
-- <eucode--** 
-- Loads a map from a file 
-- 
-- Parameters: 
--    # ##file_name_p## : The file to load from. This file may have been created 
--                          by the [[:save_map]] function. This can either be a 
--                          name of a file or an already opened file handle. 
-- 
-- Returns: 
--    Either a **map**, with all the entries found in ##file_name_p##, or **-1** 
--      if the file failed to open, or **-2** if the file is incorrectly formatted. 
-- 
-- Comments: 
-- If ##file_name_p## is an already opened file handle, this routine will write 
-- to that file and not close it. Otherwise, the named file will be created and 
-- closed by this routine. 
-- 
-- The input file can be either one created by the [[:save_map]] function or 
-- a manually created/edited text file. See [[:save_map]] for details about 
-- the required layout of the text file. 
 
And relevant details from save_map 
 
--** 
-- Saves a map to a file. 
-- 
-- Parameters: 
--    # ##m## : a map. 
--    # ##file_name_p## : Either a sequence, the name of the file to save to, 
--                         or an open file handle as returned by [[:open]](). 
--    # ##type## : an integer. SM_TEXT for a human-readable format (default), 
--                SM_RAW for a smaller and faster format, but not human-readable. 
-- 
-- Returns: 
--  An **integer**, the number of keys saved to the file, or -1 if the 
--                    save failed. 
-- 
-- Comments: 
-- If ##file_name_p## is an already opened file handle, this routine will write 
-- to that file and not close it. Otherwise, the named file will be created and 
-- closed by this routine. 
-- 
-- The SM_TEXT type saves the map keys and values in a text format which can 
-- be read and edited by standard text editor. Each entry in the map is saved as 
-- a KEY/VALUE pair in the form \\ 
-- {{{ 
-- key = value 
-- }}} 
-- Note that if the 'key' value is a normal string value, it can be enclosed in 
-- double quotes. If it is not thus quoted, the first character of the key 
-- determines its Euphoria value type. A dash or digit implies an atom, an left-brace 
-- implies a sequence, an alphabetic character implies a text string that extends to the 
-- next equal '=' symbol, and anything else is ignored.  
-- 
-- Note that if a line contains a double-dash, then all text from the double-dash 
-- to the end of the line will be ignored. This is so you can optionally add 
-- comments to the saved map. Also, any blank lines are ignored too. 
-- 
-- All text after the '=' symbol is assumed to be the map item's value data. 
-- 
-- Because some map data can be rather long, it is possible to split the text into 
-- multiple lines, which will be considered by [[:load_map]] as a single //logical// 
-- line. If an line ends with a comma (,) or a dollar sign ($), then the next actual 
-- line is appended to the end of it. After all these physical lines have been 
-- joined into one logical line, all combinations of `",$"` and `,$` are removed. 
-- 
-- For example: 
-- {{{ 
-- one = {"first", 
--        "second", 
--        "third", 
--        $ 
--       } 
-- second = "A long text ",$ 
--        "line that has been",$ 
--        " split into three lines" 
-- third = {"first", 
--        "second", 
--        "third"} 
-- }}} 
-- is equivalent to 
-- {{{ 
-- one = {"first","second","third"} 
-- second = "A long text line that has been split into three lines" 
-- third = {"first","second","third"} 
-- }}} 
-- 
-- 
-- Example 1: 
-- <eucode> 
-- include std/error.e 
-- 
-- map AppOptions 
-- if save_map(AppOptions, "c:\myapp\options.txt") = -1 
--     crash("Failed to save application options") 
-- end if 
-- 
-- if save_map(AppOptions, "c:\myapp\options.dat", SM_RAW) = -1 
--     crash("Failed to save application options") 
-- end if 
-- </eucode> 
-- 
-- See Also: 
--   [[:load_map]] 
-- 

lines 1579 to 1636

 while sequence(logical_line) with entry do  
   delim_pos = find('=', logical_line)  
   if delim_pos > 0 then  
     data_key = text:trim(logical_line[1..delim_pos-1])  
     if length(data_key) > 0 then  =  
       data_key = search:match_replace("\\-", data_key, "-")  
      if not t_alpha(data_key[1]) then  
           conv_res = stdget:value(data_key,,stdget:GET_LONG_ANSWER)  
        if conv_res[1] = stdget:GET_SUCCESS then  
           if conv_res[3] = length(data_key) then  
              data_key = conv_res[2]  
           end if  
        end if  
      end if  
      data_value = text:trim(logical_line[delim_pos+1..$])  
      data_value = search:match_replace("\\-", data_value, "-")  
      conv_res = stdget:value(data_value,,stdget:GET_LONG_ANSWER)  
      if conv_res[1] = stdget:GET_SUCCESS then  
        if conv_res[3] = length(data_value) then  
           data_value = conv_res[2]  
        end if  
      end if  
      put(new_map, data_key, data_value)  
   end if  
   end if  
 entry  
   logical_line = -1  
   while sequence(line_in) with entry do  
   if atom(logical_line) then  
      logical_line = ""  
   end if  
   has_comment = search:rmatch("--", line_in)  
     if has_comment != 0 then  
       line_in = text:trim(line_in[1..has_comment-1])  
     else  
       line_in = text:trim(line_in)  
     end if  
     logical_line &= line_in  
     if length(line_in) then  
       if not find(line_in[$], line_conts) then  
        logical_line = search:match_replace(`",$"`, logical_line, "")  
        logical_line = search:match_replace(`,$`, logical_line, "")  
        exit  
       end if  
     end if  
   entry  
     line_in = gets(file_handle)  
   end while  
 end while  

Part 1: the structure

start with the basic structure: using shorter names

 object ll, line 
 while sequence(ll) with entry do  
   ... 
 entry  
   ll = -1                                   -- not needed 
   while sequence(line) with entry do 
     if not sequence(ll) then ll = "" end if -- consequence of ll = -1 
     ... 
     if length(line) then                    -- ignoring blank lines?? 
        if line[$] not in conts then 
          -- clean ll 
          exit                               -- exit condition should be 
        end if                               -- length(ll) and not ll[$] in conts 
      end if 
   entry  
     line = gets(fh)  
   end while  
 end while                  -- but this is unsatisfactory because if ll is not ""  
                            -- and line = -1 then the loop exits with an  
                            -- incomplete ll is fed into the main loop. 
 

What is, should be, happening in the inner loop - the inner loop is combining getting ll with completing ll. Hence the mess.

 ll    line    action             correct action 
 ----------------------------------------------------- 
 ""      -1    exit inner         exit outer       -- unnecessary  
 cont    -1    exit inner         error            -- ll is incomplete  
 ""      ""    loop               loop inner 
 cont    ""    loop               error            -- comments should be separate 
 ""    line    assign exit inner  assign exit inner 
 cont  line    append exit inner  append exit inner 
 ""    cont    assign             assign 
 cont  cont    append             append 
  
 Note: it is much simpler to get ll before considering continuations 

 -- rewrite the inner loop 
 
  while TRUE label "MAIN" do 
  
   object ll,   
    
   loop do 
     ll = getline(fh)    -- ** we are not defining getline here (see Part 2) 
     if not sequence(ll) then exit "MAIN" end if 
   until length(ll) != 0 
   end loop 
    
   while find(ll[$], line_conts) do  
     object ln = getline(fh)         
     if not sequence(ln) then goto "ERROR" end if 
     if not length(ln) then goto "ERROR" end if 
   end while 
    
  -- clean ll 
  -- process ll 
  
 end while 
  

I have not included functions for getline() and clean() as they are not particularly relevant.

Part 2 errors

1 examples which ignore quotes and other structures

 has_comment = search:rmatch("--", ln)     -- note search from the right 
 if has_comment != 0 then  
   ln = text:trim(ln[1..has_comment-1])  
 else  
   ln = text:trim(ln)  
 end if  
  
 ll = search:match_replace(`",$"`, ll, "") -- assumes these sequences  
 ll = search:match_replace(`,$`, ll, "")   -- will not contain spaces 
   
 delim_pos = find('=', ll)  

2 ignoring the possible error

Where is else clause?

This silent passing over of errors is totally anti-user

 if delim_pos > 0 then  
   ... 
 end if 
 
 if length(data_key) > 0 then 
   ... 
 end if  
  
 if conv_res[1] = stdget:GET_SUCCESS then 
   ... 
 end if 
 

If one record is misread then

3 assuming data entry is correct

Assuming the line ends when there are no more continuations. Or that the line doesn't end until there are no more continuations.

are unjustified assumptions.

Lines contain sequences among other things and sequences can nest and one can have a sequence as a key or a value. One can easily miss a comma at line-end or before a comment.

Safe is to assume that blank lines and comments come between data blocks and report errors.

Why does he ignore the possibility of special characters `=,${` appearing in quotes? Why allow unquoted text?

Because this way there are no errors?

4 the true test of fidelity

If the text read in produces the same number of key-value pairs as are defined and when read out the resultant text defines the same key-value pairs as in the original then you have a successful read (of one text).

5 Conclusion

It seems to me the writer of this procedure was more taken with the cleverness of nested while with entry loop than with any integrity the program might have.

3. Re: load_map in map.e - unstructured programming example.

• Posted by mattlewis (admin) May 08, 2014
• 1467 views

I think it's a valid point. I know I've noticed times when I've thought some language feature / routine would be cool to use somewhere, but eventually realized that an apparently less elegant or clever way was actually better. I'm sure there are places where I haven't noticed that in my own code.

I don't think I wrote the load_map() stuff, and I haven't spent the time or energy to see if I agree with gimlet, but I think it's a legitimate way to criticize something.

Matt

5. Re: load_map in map.e - unstructured programming example.

• Posted by gimlet May 08, 2014
• 1462 views

The latter is more 'picking-on' than any direct criticism of code could be.

I thought it was fair comment considering the quality of code.

A key-value line is <key> = <value> where <key> and <value> are Eu objects. Lines are evaluated applying get:value() to the key and value and placed into a map.

They can also be unquoted text, which are turned into strings in Eu.

Missing a point:

Quoted text has a beginning and an end, unquoted text could contain `" = ' { }`. That is good reason to flag this as an error.

The point for insisting on quoted text is there in the specification - 'the key is everything up to the `=`' and that is exactly what the procedure does. It respects nothing not quotes, not { }.

If you insist on quotes at least a scanner can check that `=` is within quotes and therefore is part of the key.

And finally if this was the product of save_map it would appear as a sequence or a quoted string.

They work, so why would they be removed? This just seems silly.

As load_map doesn't work...

    if line[$] not in conts then  
      -- clean ll  
      exit                               -- exit condition should be  
    end if                               -- (length(ll) and not ll[$] in conts)  
 
    -- parentheses added for clarity. 

I disagree. If that were the case, wouldn't the function exit as soon as it read the first line in, regardless of line continuation? It'd break the line continuation functionality.

No the condition is double: ll has length and does not require a continuation.

As the line is appended to ll the reference to line[$] in the program is unnecessary. It also shows there is a problem with blank lines. A blank line is not a continuation line - the author ignores them. Should he? Looks like an error to me.

How do you get the logical line without completing it??? The logical line is the line that has all line continuations combined (so the multiple physical lines have already been merged into a single logical line).

Step 1 You read lines until you get one which is not empty.  
 
Step 2 If the line is not complete (ie has continuations) read lines until the line  
       is complete. 

Right: they should be if the lines are written correctly.

Verification implies that getline() should do something like this

  Read the line a character at a time. 
    on ' read a character and ' 
    on " read a string and " 
    on { increment seq 
    on } decrement seq 
    on -- ignore the rest of the line 
    on `-#0-9` read a number 
    on = and seq = 0 and equ = 0 then you have the key set equ to 1 
         else you have an error 
    on `, $` or whitespace continue 
    else you have something which should not appear in the line 
   
  as you build the line each line is submitted to getline() 
    until you have a complete key and a complete value. 
     
  This point should coincide with then end of ll 
   
  One complication is this `"` at the end if the line can be followed 
  by `,` `,$` , `,{` , `}` or nothing. Same with `'`. There may be spaces 
  between. 
 

  4 the true test of fidelity 
   
  If the text read in produces the same number of key-value pairs as are defined  
  and when read out the resultant text defines the same key-value pairs as in  
  the original then you have a successful read (of one text). 
   
  I agree, but I guess the issue is what should load_map() do on error? Should it  
  abort the program, return failure and no valid data, or keep going and get as  
  much valid data as possible? Of course it should report errors (which it sadly  
  does not), but I think it should also try to handle erors gracefully.  

What the procedure can best do is probably report an error and stop if it is a problem reading lines. If it is an error processing the line report an error and continue.

Addendum:

There is a connection between using while with entry and the structural problems of the code. I didn't spell it out because post was long enough already. I will do that another time.

It is a matter of how while with entry affects you thinking rather than any logical error in its formulation.

7. Re: load_map in map.e - unstructured programming example.

• Posted by mattlewis (admin) May 08, 2014
• 1413 views

I'm having trouble getting into this and figuring out what does or doesn't work. Could you show a failing test? Ideally in a ticket, but even a forum post would be great.

Again, a concrete example of a failing test would be light years beyond a lengthy description.

Matt

9. Re: load_map in map.e - unstructured programming example.

• Posted by DerekParnell (admin) May 08, 2014
• 1409 views
• Last edited May 09, 2014

11. Re: load_map in map.e - unstructured programming example.

• Posted by mattlewis (admin) May 09, 2014
• 1405 views

":=" = "assignment" 
"==" = "comparison" 
",$" = "placeholder" 
", $" = "erroneous - no spaces" 
"--" = "comment ---- to end of line" 

Thanks, I think that's helpful. I copied that into a file (gimlet.map), and ran the following:

include std/map.e 
include std/console.e 
 
procedure print_map( sequence file ) 
	printf(1, "\nmap loaded from %s\n", { file } ) 
	map gimlet = load_map( file ) 
	sequence keys = map:keys( gimlet ) 
	for i = 1 to length( keys ) do 
		printf(1, "key[%s] value[%s]\n", { keys[i], map:get( gimlet, keys[i] ) } ) 
	end for 
end procedure 
 
map foo = map:new() 
 
map:put( foo, `:=`, `==` ) 
map:put( foo, `==`, `comparison` ) 
map:put( foo, `,$`, `placeholder` ) 
map:put( foo, `, $`, `erroneous - no spaces` ) 
map:put( foo, `--`, `comment ---- to end of line` ) 
 
map:save_map( foo, "foo.map" ) 
print_map( "gimlet.map" ) 
print_map( "foo.map" ) 

Here was the output:

$ eui gimlet.ex  
 
map loaded from gimlet.map 
key[--] value["comment --] 
key[, $] value[erroneous - no spaces] 
key[":] value[" = "assignment"] 
key["] value[=" = "comparison"] 
 
map loaded from foo.map 
key[--] value[comment ---- to end of line] 
key[, $] value[erroneous - no spaces] 
key[":] value[" = "=="] 
key["] value[=" = "comparison"] 
 

Also, foo.map contained:

"\-\-" = "comment \-\-\-\- to end of line" 
"==" = "comparison" 
":=" = "==" 
",$" = "placeholder" 
", $" = "erroneous \- no spaces" 

Note that foo.map was created by save_map(). And load_map() returned something very different from what it should have been.

Matt

13. Re: load_map in map.e - unstructured programming example.

• Posted by jimcbrown (admin) May 09, 2014
• 1415 views

Are you going to fix this in 4.1.0 only, or will we need to make a 4.0.7 release ?

15. Re: load_map in map.e - unstructured programming example.

• Posted by SDPringle May 10, 2014
• 1353 views

I have created a ticket for this : http://openeuphoria.org/ticket/893.wc

17. Re: load_map in map.e - unstructured programming example.

• Posted by DerekParnell (admin) May 10, 2014
• 1299 views

Thanks for doing the ticket. I've updated the test case for it now.