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converting capital letters into small letters
by Karen Y 27 Jul '02

27 Jul '02

6 5

Doubts...
by Pedro L. P. Dias 27 Jul '02

27 Jul '02

Dear Professor: My name is Carlos Alexandre Grimaldi. I'm engineering student at Federal University of Rio de Janeiro, Brazil. I began my studies in Haskell, and I have some doubts which I report here. I'm very gratefully if you could help me. I'm following a book I downloaded from Internet: "A Gentle Introduction to Haskell, Version 98". Following this, I face some problems: - "inc :: Integer -> Integer" don't work - "inc n = n+1" don't work too; - "data Bool = False | True" also...; - "data Color = Red | Green | Blue | Indigo | Violet" also fails. I thought that this commands and definitions must be inside a program, and don't at prompt "prelude>". So, I opened other book, also downloaded from Internet: "The Hugs 98 User Manual", and I tryed: "module Fact where fact :: Integer -> Integer fact n = product [1..n]" thinking that would be created a file "Fact", in which the definitions for "fact" would work. But this also yield an error... So, I ask you: - is necessary the creation of a file where that definitions could work? - is this file a ".hs"? - how can I create a file like this? Which command or editor? - or, if I wrong, why that examples don't work? Thank you very much for your help. Best regards, Carlos A. Grimaldi.

2 1

RE: converting capital letters into small letters
by Garner, Robin 26 Jul '02

26 Jul '02

> 1. How would I convert capital letters into small letters? > > 2. How would I remove vowels from a string? I expect the first problem is actually to convert the upper case letters in a string to lower case, as the single-character version isn't a very interesting problem. A little thought shows that the first problem can be expressed as both a catamorphism or an anamorphism. The anamorphic solution would be [(p,f)] where p as = as == [] and f (a:as) = (makeLowerCase a, bs). The solution to the second problem is clearly a catamorphism, and one solution might be (|[],g|) where g (a:as) = if isVowel a then as else a:as The definitions of 'makeLowerCase' and 'isVowel' are quite simple (assuming English/Ascii, as pointed out in other messages), while finding the prelude functions for the patterns of recursion might take a little more thought. Suitable, possible, as homework questions in an introductory Haskell course ... Robin

1 0

Re: converting capital letters into small letters
by Ashley Yakeley 26 Jul '02

26 Jul '02

At 2002-07-25 19:07, Andrew J Bromage wrote: >> 1. How would I convert capital letters into small letters? >> 2. How would I remove vowels from a string? > >As you've probably found out, these are very hard problems. The build process of my HBase project automatically downloads the official data files from the Unicode web-site and automatically converts them into useful Haskell functions by the miracle of m4 -- including this one: toUpperCase :: Char -> Char; I also have the names for all the characters, because hard-drive space is cheap: getCharacterName :: Char -> String; ...and many other useful normative and informative character properties, such as general category, etc. See <http://sourceforge.net/projects/hbase/>. Mind you it's in a bit of an odd state right now. As for vowels, I'm pretty sure Unicode has nothing to say on the subject, as different languages may share the same characters but have different ideas as to what is and what isn't a vowel. -- Ashley Yakeley, Seattle WA

1 0

Uluslararas� �� FIRSATI..
by �� F�rsat� 26 Jul '02

26 Jul '02

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1 0

Size �zell....
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24 Jul '02

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1 0

Re: large binaries
by Jon Cast 24 Jul '02

24 Jul '02

Malcolm Wallace <Malcolm.Wallace(a)cs.york.ac.uk> wrote: > > > > Is there some reason haskell binaries have to be statically > > > > linked? > It would not be entirely fair to lay all the blame for large Haskell > binaries entirely at the door of static vs. dynamic linking. Well, considering that compiling the C binary statically linked produces an even bigger executable: $ gcc -static hello.c -o hello_c $ ls -l hello_c hello_hs -rwxrwxr-x 1 jcast jcast 441624 Jul 23 20:56 hello_c -rwxrwxr-x 1 jcast jcast 157028 Jul 18 14:08 hello_hs I think dynamic linking is fair game :) > After all, the Haskell version is dynamically linked against exactly > the same shared libraries as the C version, at least on my machine: > ldd Hello (Hello.hs) > libm.so.6 => /lib/libm.so.6 (0x40022000) > libc.so.6 => /lib/libc.so.6 (0x40044000) > /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000) > Of course, it is static linking against the *Haskell* runtime > system, Prelude and Libraries that is the cause of binary bloat. > Quite simply, lots of extra stuff is dragged in that isn't visible > in the apparently simple source program. For instance, I can find > all the following symbols in the binary for "hello world" (compiled > with nhc98): > putStr, shows, showChar, showParen, showString, fromCString, > toCString, hGetFileName, hPutChar, hPutStr, error, flip, id, init, > length, not, putChar, putStrLn, seq, show, subtract, exitWith, > instance Bounded Int (maxBound, minBound), instance Enum Ordering > (succ, pred, toEnum, fromEnum, enumFrom, enumFromThen, enumFromTo, > enumFromThenTo), instance Enum ErrNo (succ, pred, toEnum, > fromEnum, enumFrom, enumFromThen, enumFromTo, enumFromThenTo), > instance Monad IO (>>=, >>, return, fail), instance Eq ErrNo (==, > /=), instance Eq Int (==, /=), instance Eq Ordering (==, /=), > instance Num Int (+, -, *, negate, abs, signum, fromInteger), > instance Ord Int (compare, <, <=, >=, >, max, min), instance Show > ErrNo (show, showsPrec, showList), instance Show IOError (show, > showsPrec, showList), instance Show Int (show, showsPrec, showList) Well, look at the symbols I find in the statically linked C hello world: _Exit _GLOBAL_OFFSET_TABLE_ _IO_2_1_stderr_ _IO_2_1_stdin_ _IO_2_1_stdout_ _IO_adjust_column _IO_adjust_wcolumn _IO_cleanup _IO_default_doallocate _IO_default_finish _IO_default_imbue _IO_default_pbackfail _IO_default_read _IO_default_seek _IO_default_seekoff _IO_default_seekpos _IO_default_setbuf _IO_default_showmanyc _IO_default_stat _IO_default_sync _IO_default_uflow _IO_default_underflow _IO_default_write _IO_default_xsgetn _IO_default_xsputn _IO_do_write _IO_doallocbuf _IO_fclose _IO_file_attach _IO_file_close _IO_file_close_it _IO_file_doallocate _IO_file_finish _IO_file_fopen _IO_file_init _IO_file_jumps _IO_file_open _IO_file_overflow _IO_file_read _IO_file_seek _IO_file_seekoff _IO_file_setbuf _IO_file_stat _IO_file_sync _IO_file_underflow _IO_file_write _IO_file_xsgetn _IO_file_xsputn _IO_flockfile _IO_flush_all _IO_flush_all_linebuffered _IO_flush_all_lockp _IO_fopen _IO_fprintf _IO_free_backup_area _IO_free_wbackup_area 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do_length do_max_length do_out do_release_all do_release_shlib do_unshift dummy_bucket.3 empty_path_elem endmntent env_path_list environ envlock era_initialized eras errno exit expand_dynamic_string_token expected.1 expected_note.2 extend_alias_table fclose fcloseall fcntl fgets_unlocked find_derivation find_module find_module_idx fini_dummy fixup flockfile flush_cleanup fopen force_to_data force_to_data fprintf frame_dummy fread_unlocked free free_atfork free_check free_derivation free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_mem free_modules_db free_starter freemem.1 freemem_size.2 freeres fromidx fromlimit froms fseek ftrylockfile funlockfile gcc2_compiled. gcc2_compiled. gcc2_compiled. gcc2_compiled. gcc2_compiled. gconv_conf_filename gconv_module_ext gen_steps get_avphys_pages get_nprocs get_nprocs_conf get_phys_pages get_proc_path getcwd getdelim getdtablesize getegid getenv geteuid getgid getmntent_r getpagesize getpid getrlimit getuid group_number group_number gsignal guess_category_value hack_digit.0 hashfraction hasmntopt heap_trim increment_counter index init init_dummy init_dummy initial internal internal_trans_names.0 ioctl is_initialized.0 isatty isinf isinfl isnan isnanl jump_table.0 kcount kcountsize kill known_compare known_derivations known_values last_environ leaps list_all_lock list_lock llseek loaded locale_alias_path.0 localtime localtime_offset localtime_r lock lock lock lock lock lock lock.0 lock.1 log_hashfraction longjmp lose lowpc lseek lseek64 main main_arena main_trim mallinfo malloc malloc_atfork malloc_check malloc_get_state malloc_hook_ini malloc_set_state malloc_starter malloc_stats malloc_trim malloc_usable_size mallopt map map match_symbol max_capstrlen max_dirnamelen max_mmapped_mem max_n_mmaps max_sbrked_mem maxmap mbrlen mbrtowc mbsnrtowcs mem2chunk_check memalign memalign_check memalign_hook_ini memchr memcpy memmove mempcpy memset mktime mmap mmap_threshold mmapped_mem modcounter.0 mount_proc mprotect mremap msg.9 msort_with_tmp munmap n_mmaps n_mmaps_max narcs narcsp nbits.0 nbits.0 nbits.0 ncapstr new_do_write new_heap nmap not_available nsamples null num_eras num_leaps num_transitions num_types oact.0 object.2 old_tz once open open64 open_path open_verify openaux otimer.1 p.0 pagesize.1 path_proc pc_offset pc_scale phys_pages.0 phys_pages_info plone plural_eval plural_lookup plvar posix_memalign print_search_path printf printf_funcs printf_unknown profil profil_counter profile_fixup program_invocation_name program_invocation_short_name ptmalloc_init ptmalloc_init_all ptmalloc_lock_all ptmalloc_unlock_all pvalloc qsort raise rawmemchr read read_alias_file read_conf_file readlink realloc realloc_check realloc_hook_ini receiver register_printf_function release_handle result.1 rindex root rtld_search_dirs rule_dstoff rule_stdoff run_fp running samples save_arena save_for_backup save_for_wbackup save_free_hook save_malloc_hook sbrk sbrk_base search_tree setenv setitimer setlocale setmntent sigaction sigfillset siglongjmp sigprocmask sscanf stage state state state state stderr stdin stdout step0_jumps.1 step1_jumps.2 step2_jumps.3 step3a_jumps.4 step3b_jumps.5 step4_jumps.6 step4_jumps.7 stpcpy strcasecmp strchr strchrnul strcmp strcpy strdup strerror_r string_space string_space_act string_space_max strncasecmp strncmp strndup strnlen strpbrk strrchr strsep strstr strtod strtof strtol strtold strtoll strtoq strtoul strtoull strtouq sys_errlist sys_nerr sysconf system_dirs system_dirs_len tcgetattr tdelete tdestroy tdestroy_recurse textsize tfind timelocal timezone to_mb to_wc top_check top_pad tos trans_compare transcmp transitions translit_from_idx translit_from_tbl translit_to_idx translit_to_tbl transmem_list trecurse trim_threshold tsearch twalk type_idxs types tz_rules tzname tzset tzset_internal tzset_lock tzstring_list uname undefined_msg unsecure_envvars.0 unsetenv using_malloc_checking valloc vfprintf vfscanf vsscanf walt_digits walt_digits_initialized wcrtomb wcschr wcslen wcsnlen wcsrtombs wmemcpy wmemmove wmempcpy write writev yycheck yydefact yydefgoto yypact yypgoto yyr1 yyr2 yytable yytranslate zeroes zeroes zone_names The point is, /both/ libraries have a lot of code re-use. Dynamic linking puts that code re-use in some random .so in $foo/lib; static linking puts it in your executable. That's the major difference. (The minor difference is that most Haskell implementations use libc more than most C implementations use the Haskell standard libraries.) > This is not the fault of any particular implementation - the > ghc-built binary has a similar collection - rather it is dictated by > the nature of the language and its standard libraries. Because > Prelude functions are small and re-usable, they do get used all over > the place in the implementation of other parts of the Prelude, so > you end up with a huge dependency graph hiding underneath the > simplest of calls. You mean like printf("Hello, world!\n")? > In fact, most of the extra stuff in "Hello World" is there purely to > handle all possible error conditions in the I/O monad. You mean as opposed to C, where most of the extra stuff is there purely to support number formatting? > Several years ago, Colin Runciman and I did the experiment of > removing all the nice error-handling stuff from the prelude (and > eliminating a few classes too I think), to see just how small we > could squash "Hello World". The idea was to target embedded systems > where memory is a scarce resource, and fancy error-reporting is > pointless (a single red LED would do). IIRC, we managed to achieve > a size of 25kb, compiled with nhc98, which don't forget includes a > bytecode interpreter in the runtime system. > Regards, > Malcolm To sum up: code re-use within a library certainly happens in more languages than just Haskell :) So don't blame code re-use for Haskell-specific (or non-specific) problems, because code re-use is not a Haskell-specific cause. Jon Cast

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A question
by Nick Name 24 Jul '02

24 Jul '02

First, hi all. I am an haskeller newbie looking forward to conquer the world with a functional language. Part of this conquer involves IMHO writing a nice desktop, using modern features of opengl, to make it portable. But, a question arises: all opengl true type font renderers are written in C++, no one is written in C. If I want to write haskell bindings for such a thing, what can I do? Vincenzo Ciancia

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Re: conditional
by Jon Cast 23 Jul '02

23 Jul '02

Jonata Goulart <jonatahh(a)hotmail.com> wrote: > How do I write a multiple tine conditional in Haskell. I guess you mean ``line''? :) > Example: This would work on language like C. > if (x==1) { > x = x +1; > x = x +2; > x = x +3; > } Well, this example has more problems in Haskell than the multi-line if statement. I don't think you can implement a C-like `=' in Haskell 98. In GHC you can give `x' type `IORef Int', and write the first line of the conditional like this: do xval <- readIORef x x `writeIORef` (xval + 1) Note that, in Haskell, this is two lines. <aside authority="Jon's tenuous understanding"> In general, the order in which side effects (including reading mutable variables) occur depends on the evaluation order, and the meaning of the program depends on the order of side effects. Haskell expressions in general contain have very little information about the evaluation order, and therefore (if they have embedded expressions with side effects) about the program's behavior. This is bad, since the program's behavior is not obvious from the source code. The solution Haskell adopts, as I understand it, is to supply the `do' construct to make the order of evaluation explicit. So, since the C statement `x = x + 1' contains two side effects, we need to use `do' to explicitly specify the order of those side effects. </aside> This should answer your main question (almost). You write the body of a multiple line conditional the same way you write any other multiple line program: do xval <- readIORef x if xval == 1 then do xval <- readIORef x x `writeIORef` (xval + 1) xval <- readIORef x x `writeIORef` (xval + 2) xval <- readIORef x x `writeIORef` (xval + 3) else return () Note that, in Haskell, the `if' construct forms and /expression/, not a statement. Therefore, you have to provide an `else' clause. > Thanks. Jon Cast

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LRparsing combinators
by andy 23 Jul '02

23 Jul '02

Has anyone seen or have a reference to LR based parsing combinators? Andy Gill

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