Parser confused in block form of map with quote operators

[p5pRT]

Migrated from rt.perl.org#1840 (status was 'resolved')

Searchable as RT1840$

[p5pRT]

From m.pearce@inpharmatica.co.uk

[martyn]$ perl -ce 'map {qr"$x",1} @​x'
-e syntax OK
*[martyn]$ perl -ce 'map {qw"$x",1} @​x'
-e syntax OK
*[martyn]$ perl -ce 'map {qx"$x",1} @​x'
syntax error at -e line 1, next char @​
-e had compilation errors.
*[martyn]$ perl -ce 'map {q"$x",1} @​x'
syntax error at -e line 1, next char @​
-e had compilation errors.
*[martyn]$ perl -ce 'map {"$x",1} @​x'
syntax error at -e line 1, next char @​
-e had compilation errors.
*[martyn]$ perl -ce 'map {$x,1} @​x'
-e syntax OK

As shown, map seems to get confused by quotes & quotelikes with a list
return value. Making the list explicit, (e.g., by surrounding with
parens) means the parser can cope, but given the different behaviour of
qr and qq, for example, I think this must be a buglet.

This is also true of 5.005_62 .

Perl Info

Site configuration information for perl 5.00503:

Configured by matthew at Tue Apr 27 16:12:32 BST 1999.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=linux, osvers=2.2.4, archname=i586-linux
    uname='linux paddington.inpharmatica.co.uk 2.2.4 #5 tue apr 13 16:50:35 bst 1999 i586 unknown '
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef useperlio=undef d_sfio=undef
  Compiler:
    cc='gcc -pipe', optimize='-O2', gccversion=egcs-2.91.57 19980901 (egcs-1.1 release)
    cppflags='-Dbool=char -DHAS_BOOL -I/usr/local/include'
    ccflags ='-Dbool=char -DHAS_BOOL -I/usr/local/include'
    stdchar='char', d_stdstdio=undef, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='gcc -pipe', ldflags ='-s -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldb -ldl -lm -lc -lposix -lcrypt
    libc=, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    


@INC for perl 5.00503:
    /usr/local/common/martyn/Development/inpharmatica/idaps/common/db_access
    /usr/local/common/martyn/Development/inpharmatica/idaps/common/utility
    /usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/load_pdb/pdb_loading/xmas
    /usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/common_data/base_entries
    /usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/common_data/generic_loader
    /usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/common_data/writeables
    /home/victoria/martyn/devel/perl
    /export/data/test/martyn/perl/lib/site_perl/5.005/i586-linux
    /export/data/test/martyn/perl/lib/site_perl/5.005/i586-linux
    /export/data/test/martyn/perl/lib/site_perl/5.005
    /usr/lib/perl5/5.00503/i586-linux
    /usr/lib/perl5/5.00503
    /usr/lib/perl5/site_perl/5.005/i586-linux
    /usr/lib/perl5/site_perl/5.005
    .


Environment for perl 5.00503:
    HOME=/home/victoria/martyn
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/common/java/linux/jdk117_v3/bin:/data/kingsbury/test/martyn/bin:/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin:/home/victoria/martyn/bin:/data/kingsbury/test/martyn/enlightenment/bin
    PERL5LIB=/usr/local/common/martyn/Development/inpharmatica/idaps/common/db_access:/usr/local/common/martyn/Development/inpharmatica/idaps/common/utility:/usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/load_pdb/pdb_loading/xmas:/usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/common_data/base_entries:/usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/common_data/generic_loader:/usr/local/common/martyn/Development/inpharmatica/idaps/load_seq_data/common_data/writeables:/home/victoria/martyn/devel/perl:/export/data/test/martyn/perl/lib/site_perl/5.005/i586-linux:/export/data/test/martyn/perl/lib/site_perl/5.005
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[p5pRT]

From @ysth

In article <199912010856.IAA09792@​kingsbury.inpharmatica.co.uk>,
Martyn Pearce <m.pearce@​inpharmatica.co.uk> wrote​:

[martyn]$ perl -ce 'map {qr"$x",1} @​x'
-e syntax OK
*[martyn]$ perl -ce 'map {qw"$x",1} @​x'
-e syntax OK
*[martyn]$ perl -ce 'map {qx"$x",1} @​x'
syntax error at -e line 1, next char @​
-e had compilation errors.
*[martyn]$ perl -ce 'map {q"$x",1} @​x'
syntax error at -e line 1, next char @​
-e had compilation errors.
*[martyn]$ perl -ce 'map {"$x",1} @​x'
syntax error at -e line 1, next char @​
-e had compilation errors.
*[martyn]$ perl -ce 'map {$x,1} @​x'
-e syntax OK

As shown, map seems to get confused by quotes & quotelikes with a list
return value. Making the list explicit, (e.g., by surrounding with
parens) means the parser can cope, but given the different behaviour of
qr and qq, for example, I think this must be a buglet.

The error is given when these are parsed as map EXPR not map BLOCK
where the EXPR is an anonymous hash and needs a comma following it
(e.g. map {"I$_", "am in a hash"}, @​x).

Whenever you need a map {... , ...} to be unambiguously a BLOCK,
try map {; ... , ... }. As you noted, map {( ... , ...)} seems to
work also.

This leaves unanswered the question of why the different quote ops
give different results.

Also, map EXPR LIST (missing the comma) could give a more helpful error
message.

[p5pRT]

From @TimToady

sthoenna@​efn.org writes​:
: This leaves unanswered the question of why the different quote ops
: give different results.

Probably because qw and qr didn't exist when the {"a",1} dwimmer was written.
Not that I think either of those is likely at the front of an anonymous hash.
I suppose someone might write

  {qw(a 1)}

to mean

  { a => 1 }

but this dwimmer wouldn't pick that up anyway, since it's looking for
a comma or => after the first term.

: Also, map EXPR LIST (missing the comma) could give a more helpful error
: message.

Yes, it could, but not easily. A yacc is an unruly beast.

Larry