projects / OpenSPARC-T2-DV / blame
| Commit | Line | Data |
|---|---|---|
| 86530b38 AT |
1 | package Switch; |
| 2 | ||
| 3 | use strict; | |
| 4 | use vars qw($VERSION); | |
| 5 | use Carp; | |
| 6 | ||
| 7 | $VERSION = '2.09'; | |
| 8 | ||
| 9 | ||
| 10 | # LOAD FILTERING MODULE... | |
| 11 | use Filter::Util::Call; | |
| 12 | ||
| 13 | sub __(); | |
| 14 | ||
| 15 | # CATCH ATTEMPTS TO CALL case OUTSIDE THE SCOPE OF ANY switch | |
| 16 | ||
| 17 | $::_S_W_I_T_C_H = sub { croak "case/when statement not in switch/given block" }; | |
| 18 | ||
| 19 | my $offset; | |
| 20 | my $fallthrough; | |
| 21 | my ($Perl5, $Perl6) = (0,0); | |
| 22 | ||
| 23 | sub import | |
| 24 | { | |
| 25 | $fallthrough = grep /\bfallthrough\b/, @_; | |
| 26 | $offset = (caller)[2]+1; | |
| 27 | filter_add({}) unless @_>1 && $_[1] eq 'noimport'; | |
| 28 | my $pkg = caller; | |
| 29 | no strict 'refs'; | |
| 30 | for ( qw( on_defined on_exists ) ) | |
| 31 | { | |
| 32 | *{"${pkg}::$_"} = \&$_; | |
| 33 | } | |
| 34 | *{"${pkg}::__"} = \&__ if grep /__/, @_; | |
| 35 | $Perl6 = 1 if grep(/Perl\s*6/i, @_); | |
| 36 | $Perl5 = 1 if grep(/Perl\s*5/i, @_) || !grep(/Perl\s*6/i, @_); | |
| 37 | 1; | |
| 38 | } | |
| 39 | ||
| 40 | sub unimport | |
| 41 | { | |
| 42 | filter_del() | |
| 43 | } | |
| 44 | ||
| 45 | sub filter | |
| 46 | { | |
| 47 | my($self) = @_ ; | |
| 48 | local $Switch::file = (caller)[1]; | |
| 49 | ||
| 50 | my $status = 1; | |
| 51 | $status = filter_read(10_000); | |
| 52 | return $status if $status<0; | |
| 53 | $_ = filter_blocks($_,$offset); | |
| 54 | $_ = "# line $offset\n" . $_ if $offset; undef $offset; | |
| 55 | return $status; | |
| 56 | } | |
| 57 | ||
| 58 | use Text::Balanced ':ALL'; | |
| 59 | ||
| 60 | sub line | |
| 61 | { | |
| 62 | my ($pretext,$offset) = @_; | |
| 63 | ($pretext=~tr/\n/\n/)+($offset||0); | |
| 64 | } | |
| 65 | ||
| 66 | sub is_block | |
| 67 | { | |
| 68 | local $SIG{__WARN__}=sub{die$@}; | |
| 69 | local $^W=1; | |
| 70 | my $ishash = defined eval 'my $hr='.$_[0]; | |
| 71 | undef $@; | |
| 72 | return !$ishash; | |
| 73 | } | |
| 74 | ||
| 75 | ||
| 76 | my $EOP = qr/\n\n|\Z/; | |
| 77 | my $CUT = qr/\n=cut.*$EOP/; | |
| 78 | my $pod_or_DATA = qr/ ^=(?:head[1-4]|item) .*? $CUT | |
| 79 | | ^=pod .*? $CUT | |
| 80 | | ^=for .*? $EOP | |
| 81 | | ^=begin \s* (\S+) .*? \n=end \s* \1 .*? $EOP | |
| 82 | | ^__(DATA|END)__\n.* | |
| 83 | /smx; | |
| 84 | ||
| 85 | my $casecounter = 1; | |
| 86 | sub filter_blocks | |
| 87 | { | |
| 88 | my ($source, $line) = @_; | |
| 89 | return $source unless $Perl5 && $source =~ /case|switch/ | |
| 90 | || $Perl6 && $source =~ /when|given/; | |
| 91 | pos $source = 0; | |
| 92 | my $text = ""; | |
| 93 | $DB::single = 1; | |
| 94 | component: while (pos $source < length $source) | |
| 95 | { | |
| 96 | if ($source =~ m/(\G\s*use\s+Switch\b)/gc) | |
| 97 | { | |
| 98 | $text .= q{use Switch 'noimport'}; | |
| 99 | next component; | |
| 100 | } | |
| 101 | my @pos = Text::Balanced::_match_quotelike(\$source,qr/\s*/,1,0); | |
| 102 | if (defined $pos[0]) | |
| 103 | { | |
| 104 | $text .= " " . substr($source,$pos[2],$pos[18]-$pos[2]); | |
| 105 | next component; | |
| 106 | } | |
| 107 | if ($source =~ m/\G\s*($pod_or_DATA)/gc) { | |
| 108 | next component; | |
| 109 | } | |
| 110 | @pos = Text::Balanced::_match_variable(\$source,qr/\s*/); | |
| 111 | if (defined $pos[0]) | |
| 112 | { | |
| 113 | $text .= " " . substr($source,$pos[0],$pos[4]-$pos[0]); | |
| 114 | next component; | |
| 115 | } | |
| 116 | ||
| 117 | if ($Perl5 && $source =~ m/\G(\n*)(\s*)(switch)\b(?=\s*[(])/gc | |
| 118 | || $Perl6 && $source =~ m/\G(\n*)(\s*)(given)\b(?=\s*[(])/gc | |
| 119 | || $Perl6 && $source =~ m/\G(\n*)(\s*)(given)\b(.*)(?=\{)/gc) | |
| 120 | { | |
| 121 | my $keyword = $3; | |
| 122 | my $arg = $4; | |
| 123 | # print STDERR "[$arg]\n"; | |
| 124 | $text .= $1.$2.'S_W_I_T_C_H: while (1) '; | |
| 125 | unless ($arg) { | |
| 126 | @pos = Text::Balanced::_match_codeblock(\$source,qr/\s*/,qr/\(/,qr/\)/,qr/[[{(<]/,qr/[]})>]/,undef) | |
| 127 | or do { | |
| 128 | die "Bad $keyword statement (problem in the parentheses?) near $Switch::file line ", line(substr($source,0,pos $source),$line), "\n"; | |
| 129 | }; | |
| 130 | $arg = filter_blocks(substr($source,$pos[0],$pos[4]-$pos[0]),line(substr($source,0,$pos[0]),$line)); | |
| 131 | } | |
| 132 | $arg =~ s {^\s*[(]\s*%} { ( \\\%} || | |
| 133 | $arg =~ s {^\s*[(]\s*m\b} { ( qr} || | |
| 134 | $arg =~ s {^\s*[(]\s*/} { ( qr/} || | |
| 135 | $arg =~ s {^\s*[(]\s*qw} { ( \\qw}; | |
| 136 | @pos = Text::Balanced::_match_codeblock(\$source,qr/\s*/,qr/\{/,qr/\}/,qr/\{/,qr/\}/,undef) | |
| 137 | or do { | |
| 138 | die "Bad $keyword statement (problem in the code block?) near $Switch::file line ", line(substr($source,0, pos $source), $line), "\n"; | |
| 139 | }; | |
| 140 | my $code = filter_blocks(substr($source,$pos[0],$pos[4]-$pos[0]),line(substr($source,0,$pos[0]),$line)); | |
| 141 | $code =~ s/{/{ local \$::_S_W_I_T_C_H; Switch::switch $arg;/; | |
| 142 | $text .= $code . 'continue {last}'; | |
| 143 | next component; | |
| 144 | } | |
| 145 | elsif ($Perl5 && $source =~ m/\G(\s*)(case\b)(?!\s*=>)/gc | |
| 146 | || $Perl6 && $source =~ m/\G(\s*)(when\b)(?!\s*=>)/gc) | |
| 147 | { | |
| 148 | my $keyword = $2; | |
| 149 | $text .= $1."if (Switch::case"; | |
| 150 | if (@pos = Text::Balanced::_match_codeblock(\$source,qr/\s*/,qr/\{/,qr/\}/,qr/\{/,qr/\}/,undef)) { | |
| 151 | my $code = substr($source,$pos[0],$pos[4]-$pos[0]); | |
| 152 | $text .= " sub" if is_block $code; | |
| 153 | $text .= " " . filter_blocks($code,line(substr($source,0,$pos[0]),$line)) . ")"; | |
| 154 | } | |
| 155 | elsif (@pos = Text::Balanced::_match_codeblock(\$source,qr/\s*/,qr/[[(]/,qr/[])]/,qr/[[({]/,qr/[])}]/,undef)) { | |
| 156 | my $code = filter_blocks(substr($source,$pos[0],$pos[4]-$pos[0]),line(substr($source,0,$pos[0]),$line)); | |
| 157 | $code =~ s {^\s*[(]\s*%} { ( \\\%} || | |
| 158 | $code =~ s {^\s*[(]\s*m\b} { ( qr} || | |
| 159 | $code =~ s {^\s*[(]\s*/} { ( qr/} || | |
| 160 | $code =~ s {^\s*[(]\s*qw} { ( \\qw}; | |
| 161 | $text .= " $code)"; | |
| 162 | } | |
| 163 | elsif ($Perl6 && do{@pos = Text::Balanced::_match_variable(\$source,qr/\s*/)}) { | |
| 164 | my $code = filter_blocks(substr($source,$pos[0],$pos[4]-$pos[0]),line(substr($source,0,$pos[0]),$line)); | |
| 165 | $code =~ s {^\s*%} { \%} || | |
| 166 | $code =~ s {^\s*@} { \@}; | |
| 167 | $text .= " $code)"; | |
| 168 | } | |
| 169 | elsif ( @pos = Text::Balanced::_match_quotelike(\$source,qr/\s*/,1,0)) { | |
| 170 | my $code = substr($source,$pos[2],$pos[18]-$pos[2]); | |
| 171 | $code = filter_blocks($code,line(substr($source,0,$pos[2]),$line)); | |
| 172 | $code =~ s {^\s*m} { qr} || | |
| 173 | $code =~ s {^\s*/} { qr/} || | |
| 174 | $code =~ s {^\s*qw} { \\qw}; | |
| 175 | $text .= " $code)"; | |
| 176 | } | |
| 177 | elsif ($Perl5 && $source =~ m/\G\s*(([^\$\@{])[^\$\@{]*)(?=\s*{)/gc | |
| 178 | || $Perl6 && $source =~ m/\G\s*([^;{]*)()/gc) { | |
| 179 | my $code = filter_blocks($1,line(substr($source,0,pos $source),$line)); | |
| 180 | $text .= ' \\' if $2 eq '%'; | |
| 181 | $text .= " $code)"; | |
| 182 | } | |
| 183 | else { | |
| 184 | die "Bad $keyword statement (invalid $keyword value?) near $Switch::file line ", line(substr($source,0,pos $source), $line), "\n"; | |
| 185 | } | |
| 186 | ||
| 187 | die "Missing opening brace or semi-colon after 'when' value near $Switch::file line ", line(substr($source,0,pos $source), $line), "\n" | |
| 188 | unless !$Perl6 || $source =~ m/\G(\s*)(?=;|\{)/gc; | |
| 189 | ||
| 190 | do{@pos = Text::Balanced::_match_codeblock(\$source,qr/\s*/,qr/\{/,qr/\}/,qr/\{/,qr/\}/,undef)} | |
| 191 | or do { | |
| 192 | if ($source =~ m/\G\s*(?=([};]|\Z))/gc) { | |
| 193 | $casecounter++; | |
| 194 | next component; | |
| 195 | } | |
| 196 | die "Bad $keyword statement (problem in the code block?) near $Switch::file line ", line(substr($source,0,pos $source),$line), "\n"; | |
| 197 | }; | |
| 198 | my $code = filter_blocks(substr($source,$pos[0],$pos[4]-$pos[0]),line(substr($source,0,$pos[0]),$line)); | |
| 199 | $code =~ s/}(?=\s*\Z)/;last S_W_I_T_C_H }/ | |
| 200 | unless $fallthrough; | |
| 201 | $text .= "{ while (1) $code continue { goto C_A_S_E_$casecounter } last S_W_I_T_C_H; C_A_S_E_$casecounter: }"; | |
| 202 | $casecounter++; | |
| 203 | next component; | |
| 204 | } | |
| 205 | ||
| 206 | $source =~ m/\G(\s*(-[sm]\s+|\w+|#.*\n|\W))/gc; | |
| 207 | $text .= $1; | |
| 208 | } | |
| 209 | $text; | |
| 210 | } | |
| 211 | ||
| 212 | ||
| 213 | ||
| 214 | sub in | |
| 215 | { | |
| 216 | my ($x,$y) = @_; | |
| 217 | my @numy; | |
| 218 | for my $nextx ( @$x ) | |
| 219 | { | |
| 220 | my $numx = ref($nextx) || defined $nextx && (~$nextx&$nextx) eq 0; | |
| 221 | for my $j ( 0..$#$y ) | |
| 222 | { | |
| 223 | my $nexty = $y->[$j]; | |
| 224 | push @numy, ref($nexty) || defined $nexty && (~$nexty&$nexty) eq 0 | |
| 225 | if @numy <= $j; | |
| 226 | return 1 if $numx && $numy[$j] && $nextx==$nexty | |
| 227 | || $nextx eq $nexty; | |
| 228 | ||
| 229 | } | |
| 230 | } | |
| 231 | return ""; | |
| 232 | } | |
| 233 | ||
| 234 | sub on_exists | |
| 235 | { | |
| 236 | my $ref = @_==1 && ref($_[0]) eq 'HASH' ? $_[0] : { @_ }; | |
| 237 | [ keys %$ref ] | |
| 238 | } | |
| 239 | ||
| 240 | sub on_defined | |
| 241 | { | |
| 242 | my $ref = @_==1 && ref($_[0]) eq 'HASH' ? $_[0] : { @_ }; | |
| 243 | [ grep { defined $ref->{$_} } keys %$ref ] | |
| 244 | } | |
| 245 | ||
| 246 | sub switch(;$) | |
| 247 | { | |
| 248 | my ($s_val) = @_ ? $_[0] : $_; | |
| 249 | my $s_ref = ref $s_val; | |
| 250 | ||
| 251 | if ($s_ref eq 'CODE') | |
| 252 | { | |
| 253 | $::_S_W_I_T_C_H = | |
| 254 | sub { my $c_val = $_[0]; | |
| 255 | return $s_val == $c_val if ref $c_val eq 'CODE'; | |
| 256 | return $s_val->(@$c_val) if ref $c_val eq 'ARRAY'; | |
| 257 | return $s_val->($c_val); | |
| 258 | }; | |
| 259 | } | |
| 260 | elsif ($s_ref eq "" && defined $s_val && (~$s_val&$s_val) eq 0) # NUMERIC SCALAR | |
| 261 | { | |
| 262 | $::_S_W_I_T_C_H = | |
| 263 | sub { my $c_val = $_[0]; | |
| 264 | my $c_ref = ref $c_val; | |
| 265 | return $s_val == $c_val if $c_ref eq "" | |
| 266 | && defined $c_val | |
| 267 | && (~$c_val&$c_val) eq 0; | |
| 268 | return $s_val eq $c_val if $c_ref eq ""; | |
| 269 | return in([$s_val],$c_val) if $c_ref eq 'ARRAY'; | |
| 270 | return $c_val->($s_val) if $c_ref eq 'CODE'; | |
| 271 | return $c_val->call($s_val) if $c_ref eq 'Switch'; | |
| 272 | return scalar $s_val=~/$c_val/ | |
| 273 | if $c_ref eq 'Regexp'; | |
| 274 | return scalar $c_val->{$s_val} | |
| 275 | if $c_ref eq 'HASH'; | |
| 276 | return; | |
| 277 | }; | |
| 278 | } | |
| 279 | elsif ($s_ref eq "") # STRING SCALAR | |
| 280 | { | |
| 281 | $::_S_W_I_T_C_H = | |
| 282 | sub { my $c_val = $_[0]; | |
| 283 | my $c_ref = ref $c_val; | |
| 284 | return $s_val eq $c_val if $c_ref eq ""; | |
| 285 | return in([$s_val],$c_val) if $c_ref eq 'ARRAY'; | |
| 286 | return $c_val->($s_val) if $c_ref eq 'CODE'; | |
| 287 | return $c_val->call($s_val) if $c_ref eq 'Switch'; | |
| 288 | return scalar $s_val=~/$c_val/ | |
| 289 | if $c_ref eq 'Regexp'; | |
| 290 | return scalar $c_val->{$s_val} | |
| 291 | if $c_ref eq 'HASH'; | |
| 292 | return; | |
| 293 | }; | |
| 294 | } | |
| 295 | elsif ($s_ref eq 'ARRAY') | |
| 296 | { | |
| 297 | $::_S_W_I_T_C_H = | |
| 298 | sub { my $c_val = $_[0]; | |
| 299 | my $c_ref = ref $c_val; | |
| 300 | return in($s_val,[$c_val]) if $c_ref eq ""; | |
| 301 | return in($s_val,$c_val) if $c_ref eq 'ARRAY'; | |
| 302 | return $c_val->(@$s_val) if $c_ref eq 'CODE'; | |
| 303 | return $c_val->call(@$s_val) | |
| 304 | if $c_ref eq 'Switch'; | |
| 305 | return scalar grep {$_=~/$c_val/} @$s_val | |
| 306 | if $c_ref eq 'Regexp'; | |
| 307 | return scalar grep {$c_val->{$_}} @$s_val | |
| 308 | if $c_ref eq 'HASH'; | |
| 309 | return; | |
| 310 | }; | |
| 311 | } | |
| 312 | elsif ($s_ref eq 'Regexp') | |
| 313 | { | |
| 314 | $::_S_W_I_T_C_H = | |
| 315 | sub { my $c_val = $_[0]; | |
| 316 | my $c_ref = ref $c_val; | |
| 317 | return $c_val=~/s_val/ if $c_ref eq ""; | |
| 318 | return scalar grep {$_=~/s_val/} @$c_val | |
| 319 | if $c_ref eq 'ARRAY'; | |
| 320 | return $c_val->($s_val) if $c_ref eq 'CODE'; | |
| 321 | return $c_val->call($s_val) if $c_ref eq 'Switch'; | |
| 322 | return $s_val eq $c_val if $c_ref eq 'Regexp'; | |
| 323 | return grep {$_=~/$s_val/ && $c_val->{$_}} keys %$c_val | |
| 324 | if $c_ref eq 'HASH'; | |
| 325 | return; | |
| 326 | }; | |
| 327 | } | |
| 328 | elsif ($s_ref eq 'HASH') | |
| 329 | { | |
| 330 | $::_S_W_I_T_C_H = | |
| 331 | sub { my $c_val = $_[0]; | |
| 332 | my $c_ref = ref $c_val; | |
| 333 | return $s_val->{$c_val} if $c_ref eq ""; | |
| 334 | return scalar grep {$s_val->{$_}} @$c_val | |
| 335 | if $c_ref eq 'ARRAY'; | |
| 336 | return $c_val->($s_val) if $c_ref eq 'CODE'; | |
| 337 | return $c_val->call($s_val) if $c_ref eq 'Switch'; | |
| 338 | return grep {$_=~/$c_val/ && $s_val->{"$_"}} keys %$s_val | |
| 339 | if $c_ref eq 'Regexp'; | |
| 340 | return $s_val==$c_val if $c_ref eq 'HASH'; | |
| 341 | return; | |
| 342 | }; | |
| 343 | } | |
| 344 | elsif ($s_ref eq 'Switch') | |
| 345 | { | |
| 346 | $::_S_W_I_T_C_H = | |
| 347 | sub { my $c_val = $_[0]; | |
| 348 | return $s_val == $c_val if ref $c_val eq 'Switch'; | |
| 349 | return $s_val->call(@$c_val) | |
| 350 | if ref $c_val eq 'ARRAY'; | |
| 351 | return $s_val->call($c_val); | |
| 352 | }; | |
| 353 | } | |
| 354 | else | |
| 355 | { | |
| 356 | croak "Cannot switch on $s_ref"; | |
| 357 | } | |
| 358 | return 1; | |
| 359 | } | |
| 360 | ||
| 361 | sub case($) { local $SIG{__WARN__} = \&carp; | |
| 362 | $::_S_W_I_T_C_H->(@_); } | |
| 363 | ||
| 364 | # IMPLEMENT __ | |
| 365 | ||
| 366 | my $placeholder = bless { arity=>1, impl=>sub{$_[1+$_[0]]} }; | |
| 367 | ||
| 368 | sub __() { $placeholder } | |
| 369 | ||
| 370 | sub __arg($) | |
| 371 | { | |
| 372 | my $index = $_[0]+1; | |
| 373 | bless { arity=>0, impl=>sub{$_[$index]} }; | |
| 374 | } | |
| 375 | ||
| 376 | sub hosub(&@) | |
| 377 | { | |
| 378 | # WRITE THIS | |
| 379 | } | |
| 380 | ||
| 381 | sub call | |
| 382 | { | |
| 383 | my ($self,@args) = @_; | |
| 384 | return $self->{impl}->(0,@args); | |
| 385 | } | |
| 386 | ||
| 387 | sub meta_bop(&) | |
| 388 | { | |
| 389 | my ($op) = @_; | |
| 390 | sub | |
| 391 | { | |
| 392 | my ($left, $right, $reversed) = @_; | |
| 393 | ($right,$left) = @_ if $reversed; | |
| 394 | ||
| 395 | my $rop = ref $right eq 'Switch' | |
| 396 | ? $right | |
| 397 | : bless { arity=>0, impl=>sub{$right} }; | |
| 398 | ||
| 399 | my $lop = ref $left eq 'Switch' | |
| 400 | ? $left | |
| 401 | : bless { arity=>0, impl=>sub{$left} }; | |
| 402 | ||
| 403 | my $arity = $lop->{arity} + $rop->{arity}; | |
| 404 | ||
| 405 | return bless { | |
| 406 | arity => $arity, | |
| 407 | impl => sub { my $start = shift; | |
| 408 | return $op->($lop->{impl}->($start,@_), | |
| 409 | $rop->{impl}->($start+$lop->{arity},@_)); | |
| 410 | } | |
| 411 | }; | |
| 412 | }; | |
| 413 | } | |
| 414 | ||
| 415 | sub meta_uop(&) | |
| 416 | { | |
| 417 | my ($op) = @_; | |
| 418 | sub | |
| 419 | { | |
| 420 | my ($left) = @_; | |
| 421 | ||
| 422 | my $lop = ref $left eq 'Switch' | |
| 423 | ? $left | |
| 424 | : bless { arity=>0, impl=>sub{$left} }; | |
| 425 | ||
| 426 | my $arity = $lop->{arity}; | |
| 427 | ||
| 428 | return bless { | |
| 429 | arity => $arity, | |
| 430 | impl => sub { $op->($lop->{impl}->(@_)) } | |
| 431 | }; | |
| 432 | }; | |
| 433 | } | |
| 434 | ||
| 435 | ||
| 436 | use overload | |
| 437 | "+" => meta_bop {$_[0] + $_[1]}, | |
| 438 | "-" => meta_bop {$_[0] - $_[1]}, | |
| 439 | "*" => meta_bop {$_[0] * $_[1]}, | |
| 440 | "/" => meta_bop {$_[0] / $_[1]}, | |
| 441 | "%" => meta_bop {$_[0] % $_[1]}, | |
| 442 | "**" => meta_bop {$_[0] ** $_[1]}, | |
| 443 | "<<" => meta_bop {$_[0] << $_[1]}, | |
| 444 | ">>" => meta_bop {$_[0] >> $_[1]}, | |
| 445 | "x" => meta_bop {$_[0] x $_[1]}, | |
| 446 | "." => meta_bop {$_[0] . $_[1]}, | |
| 447 | "<" => meta_bop {$_[0] < $_[1]}, | |
| 448 | "<=" => meta_bop {$_[0] <= $_[1]}, | |
| 449 | ">" => meta_bop {$_[0] > $_[1]}, | |
| 450 | ">=" => meta_bop {$_[0] >= $_[1]}, | |
| 451 | "==" => meta_bop {$_[0] == $_[1]}, | |
| 452 | "!=" => meta_bop {$_[0] != $_[1]}, | |
| 453 | "<=>" => meta_bop {$_[0] <=> $_[1]}, | |
| 454 | "lt" => meta_bop {$_[0] lt $_[1]}, | |
| 455 | "le" => meta_bop {$_[0] le $_[1]}, | |
| 456 | "gt" => meta_bop {$_[0] gt $_[1]}, | |
| 457 | "ge" => meta_bop {$_[0] ge $_[1]}, | |
| 458 | "eq" => meta_bop {$_[0] eq $_[1]}, | |
| 459 | "ne" => meta_bop {$_[0] ne $_[1]}, | |
| 460 | "cmp" => meta_bop {$_[0] cmp $_[1]}, | |
| 461 | "\&" => meta_bop {$_[0] & $_[1]}, | |
| 462 | "^" => meta_bop {$_[0] ^ $_[1]}, | |
| 463 | "|" => meta_bop {$_[0] | $_[1]}, | |
| 464 | "atan2" => meta_bop {atan2 $_[0], $_[1]}, | |
| 465 | ||
| 466 | "neg" => meta_uop {-$_[0]}, | |
| 467 | "!" => meta_uop {!$_[0]}, | |
| 468 | "~" => meta_uop {~$_[0]}, | |
| 469 | "cos" => meta_uop {cos $_[0]}, | |
| 470 | "sin" => meta_uop {sin $_[0]}, | |
| 471 | "exp" => meta_uop {exp $_[0]}, | |
| 472 | "abs" => meta_uop {abs $_[0]}, | |
| 473 | "log" => meta_uop {log $_[0]}, | |
| 474 | "sqrt" => meta_uop {sqrt $_[0]}, | |
| 475 | "bool" => sub { croak "Can't use && or || in expression containing __" }, | |
| 476 | ||
| 477 | # "&()" => sub { $_[0]->{impl} }, | |
| 478 | ||
| 479 | # "||" => meta_bop {$_[0] || $_[1]}, | |
| 480 | # "&&" => meta_bop {$_[0] && $_[1]}, | |
| 481 | # fallback => 1, | |
| 482 | ; | |
| 483 | 1; | |
| 484 | ||
| 485 | __END__ | |
| 486 | ||
| 487 | ||
| 488 | =head1 NAME | |
| 489 | ||
| 490 | Switch - A switch statement for Perl | |
| 491 | ||
| 492 | =head1 VERSION | |
| 493 | ||
| 494 | This document describes version 2.09 of Switch, | |
| 495 | released June 12, 2002. | |
| 496 | ||
| 497 | =head1 SYNOPSIS | |
| 498 | ||
| 499 | use Switch; | |
| 500 | ||
| 501 | switch ($val) { | |
| 502 | ||
| 503 | case 1 { print "number 1" } | |
| 504 | case "a" { print "string a" } | |
| 505 | case [1..10,42] { print "number in list" } | |
| 506 | case (@array) { print "number in list" } | |
| 507 | case /\w+/ { print "pattern" } | |
| 508 | case qr/\w+/ { print "pattern" } | |
| 509 | case (%hash) { print "entry in hash" } | |
| 510 | case (\%hash) { print "entry in hash" } | |
| 511 | case (\&sub) { print "arg to subroutine" } | |
| 512 | else { print "previous case not true" } | |
| 513 | } | |
| 514 | ||
| 515 | =head1 BACKGROUND | |
| 516 | ||
| 517 | [Skip ahead to L<"DESCRIPTION"> if you don't care about the whys | |
| 518 | and wherefores of this control structure] | |
| 519 | ||
| 520 | In seeking to devise a "Swiss Army" case mechanism suitable for Perl, | |
| 521 | it is useful to generalize this notion of distributed conditional | |
| 522 | testing as far as possible. Specifically, the concept of "matching" | |
| 523 | between the switch value and the various case values need not be | |
| 524 | restricted to numeric (or string or referential) equality, as it is in other | |
| 525 | languages. Indeed, as Table 1 illustrates, Perl | |
| 526 | offers at least eighteen different ways in which two values could | |
| 527 | generate a match. | |
| 528 | ||
| 529 | Table 1: Matching a switch value ($s) with a case value ($c) | |
| 530 | ||
| 531 | Switch Case Type of Match Implied Matching Code | |
| 532 | Value Value | |
| 533 | ====== ===== ===================== ============= | |
| 534 | ||
| 535 | number same numeric or referential match if $s == $c; | |
| 536 | or ref equality | |
| 537 | ||
| 538 | object method result of method call match if $s->$c(); | |
| 539 | ref name match if defined $s->$c(); | |
| 540 | or ref | |
| 541 | ||
| 542 | other other string equality match if $s eq $c; | |
| 543 | non-ref non-ref | |
| 544 | scalar scalar | |
| 545 | ||
| 546 | string regexp pattern match match if $s =~ /$c/; | |
| 547 | ||
| 548 | array scalar array entry existence match if 0<=$c && $c<@$s; | |
| 549 | ref array entry definition match if defined $s->[$c]; | |
| 550 | array entry truth match if $s->[$c]; | |
| 551 | ||
| 552 | array array array intersection match if intersects(@$s, @$c); | |
| 553 | ref ref (apply this table to | |
| 554 | all pairs of elements | |
| 555 | $s->[$i] and | |
| 556 | $c->[$j]) | |
| 557 | ||
| 558 | array regexp array grep match if grep /$c/, @$s; | |
| 559 | ref | |
| 560 | ||
| 561 | hash scalar hash entry existence match if exists $s->{$c}; | |
| 562 | ref hash entry definition match if defined $s->{$c}; | |
| 563 | hash entry truth match if $s->{$c}; | |
| 564 | ||
| 565 | hash regexp hash grep match if grep /$c/, keys %$s; | |
| 566 | ref | |
| 567 | ||
| 568 | sub scalar return value defn match if defined $s->($c); | |
| 569 | ref return value truth match if $s->($c); | |
| 570 | ||
| 571 | sub array return value defn match if defined $s->(@$c); | |
| 572 | ref ref return value truth match if $s->(@$c); | |
| 573 | ||
| 574 | ||
| 575 | In reality, Table 1 covers 31 alternatives, because only the equality and | |
| 576 | intersection tests are commutative; in all other cases, the roles of | |
| 577 | the C<$s> and C<$c> variables could be reversed to produce a | |
| 578 | different test. For example, instead of testing a single hash for | |
| 579 | the existence of a series of keys (C<match if exists $s-E<gt>{$c}>), | |
| 580 | one could test for the existence of a single key in a series of hashes | |
| 581 | (C<match if exists $c-E<gt>{$s}>). | |
| 582 | ||
| 583 | As L<perltodo> observes, a Perl case mechanism must support all these | |
| 584 | "ways to do it". | |
| 585 | ||
| 586 | ||
| 587 | =head1 DESCRIPTION | |
| 588 | ||
| 589 | The Switch.pm module implements a generalized case mechanism that covers | |
| 590 | the numerous possible combinations of switch and case values described above. | |
| 591 | ||
| 592 | The module augments the standard Perl syntax with two new control | |
| 593 | statements: C<switch> and C<case>. The C<switch> statement takes a | |
| 594 | single scalar argument of any type, specified in parentheses. | |
| 595 | C<switch> stores this value as the | |
| 596 | current switch value in a (localized) control variable. | |
| 597 | The value is followed by a block which may contain one or more | |
| 598 | Perl statements (including the C<case> statement described below). | |
| 599 | The block is unconditionally executed once the switch value has | |
| 600 | been cached. | |
| 601 | ||
| 602 | A C<case> statement takes a single scalar argument (in mandatory | |
| 603 | parentheses if it's a variable; otherwise the parens are optional) and | |
| 604 | selects the appropriate type of matching between that argument and the | |
| 605 | current switch value. The type of matching used is determined by the | |
| 606 | respective types of the switch value and the C<case> argument, as | |
| 607 | specified in Table 1. If the match is successful, the mandatory | |
| 608 | block associated with the C<case> statement is executed. | |
| 609 | ||
| 610 | In most other respects, the C<case> statement is semantically identical | |
| 611 | to an C<if> statement. For example, it can be followed by an C<else> | |
| 612 | clause, and can be used as a postfix statement qualifier. | |
| 613 | ||
| 614 | However, when a C<case> block has been executed control is automatically | |
| 615 | transferred to the statement after the immediately enclosing C<switch> | |
| 616 | block, rather than to the next statement within the block. In other | |
| 617 | words, the success of any C<case> statement prevents other cases in the | |
| 618 | same scope from executing. But see L<"Allowing fall-through"> below. | |
| 619 | ||
| 620 | Together these two new statements provide a fully generalized case | |
| 621 | mechanism: | |
| 622 | ||
| 623 | use Switch; | |
| 624 | ||
| 625 | # AND LATER... | |
| 626 | ||
| 627 | %special = ( woohoo => 1, d'oh => 1 ); | |
| 628 | ||
| 629 | while (<>) { | |
| 630 | switch ($_) { | |
| 631 | ||
| 632 | case (%special) { print "homer\n"; } # if $special{$_} | |
| 633 | case /a-z/i { print "alpha\n"; } # if $_ =~ /a-z/i | |
| 634 | case [1..9] { print "small num\n"; } # if $_ in [1..9] | |
| 635 | ||
| 636 | case { $_[0] >= 10 } { # if $_ >= 10 | |
| 637 | my $age = <>; | |
| 638 | switch (sub{ $_[0] < $age } ) { | |
| 639 | ||
| 640 | case 20 { print "teens\n"; } # if 20 < $age | |
| 641 | case 30 { print "twenties\n"; } # if 30 < $age | |
| 642 | else { print "history\n"; } | |
| 643 | } | |
| 644 | } | |
| 645 | ||
| 646 | print "must be punctuation\n" case /\W/; # if $_ ~= /\W/ | |
| 647 | } | |
| 648 | ||
| 649 | Note that C<switch>es can be nested within C<case> (or any other) blocks, | |
| 650 | and a series of C<case> statements can try different types of matches | |
| 651 | -- hash membership, pattern match, array intersection, simple equality, | |
| 652 | etc. -- against the same switch value. | |
| 653 | ||
| 654 | The use of intersection tests against an array reference is particularly | |
| 655 | useful for aggregating integral cases: | |
| 656 | ||
| 657 | sub classify_digit | |
| 658 | { | |
| 659 | switch ($_[0]) { case 0 { return 'zero' } | |
| 660 | case [2,4,6,8] { return 'even' } | |
| 661 | case [1,3,4,7,9] { return 'odd' } | |
| 662 | case /[A-F]/i { return 'hex' } | |
| 663 | } | |
| 664 | } | |
| 665 | ||
| 666 | ||
| 667 | =head2 Allowing fall-through | |
| 668 | ||
| 669 | Fall-though (trying another case after one has already succeeded) | |
| 670 | is usually a Bad Idea in a switch statement. However, this | |
| 671 | is Perl, not a police state, so there I<is> a way to do it, if you must. | |
| 672 | ||
| 673 | If a C<case> block executes an untargetted C<next>, control is | |
| 674 | immediately transferred to the statement I<after> the C<case> statement | |
| 675 | (i.e. usually another case), rather than out of the surrounding | |
| 676 | C<switch> block. | |
| 677 | ||
| 678 | For example: | |
| 679 | ||
| 680 | switch ($val) { | |
| 681 | case 1 { handle_num_1(); next } # and try next case... | |
| 682 | case "1" { handle_str_1(); next } # and try next case... | |
| 683 | case [0..9] { handle_num_any(); } # and we're done | |
| 684 | case /\d/ { handle_dig_any(); next } # and try next case... | |
| 685 | case /.*/ { handle_str_any(); next } # and try next case... | |
| 686 | } | |
| 687 | ||
| 688 | If $val held the number C<1>, the above C<switch> block would call the | |
| 689 | first three C<handle_...> subroutines, jumping to the next case test | |
| 690 | each time it encountered a C<next>. After the thrid C<case> block | |
| 691 | was executed, control would jump to the end of the enclosing | |
| 692 | C<switch> block. | |
| 693 | ||
| 694 | On the other hand, if $val held C<10>, then only the last two C<handle_...> | |
| 695 | subroutines would be called. | |
| 696 | ||
| 697 | Note that this mechanism allows the notion of I<conditional fall-through>. | |
| 698 | For example: | |
| 699 | ||
| 700 | switch ($val) { | |
| 701 | case [0..9] { handle_num_any(); next if $val < 7; } | |
| 702 | case /\d/ { handle_dig_any(); } | |
| 703 | } | |
| 704 | ||
| 705 | If an untargetted C<last> statement is executed in a case block, this | |
| 706 | immediately transfers control out of the enclosing C<switch> block | |
| 707 | (in other words, there is an implicit C<last> at the end of each | |
| 708 | normal C<case> block). Thus the previous example could also have been | |
| 709 | written: | |
| 710 | ||
| 711 | switch ($val) { | |
| 712 | case [0..9] { handle_num_any(); last if $val >= 7; next; } | |
| 713 | case /\d/ { handle_dig_any(); } | |
| 714 | } | |
| 715 | ||
| 716 | ||
| 717 | =head2 Automating fall-through | |
| 718 | ||
| 719 | In situations where case fall-through should be the norm, rather than an | |
| 720 | exception, an endless succession of terminal C<next>s is tedious and ugly. | |
| 721 | Hence, it is possible to reverse the default behaviour by specifying | |
| 722 | the string "fallthrough" when importing the module. For example, the | |
| 723 | following code is equivalent to the first example in L<"Allowing fall-through">: | |
| 724 | ||
| 725 | use Switch 'fallthrough'; | |
| 726 | ||
| 727 | switch ($val) { | |
| 728 | case 1 { handle_num_1(); } | |
| 729 | case "1" { handle_str_1(); } | |
| 730 | case [0..9] { handle_num_any(); last } | |
| 731 | case /\d/ { handle_dig_any(); } | |
| 732 | case /.*/ { handle_str_any(); } | |
| 733 | } | |
| 734 | ||
| 735 | Note the explicit use of a C<last> to preserve the non-fall-through | |
| 736 | behaviour of the third case. | |
| 737 | ||
| 738 | ||
| 739 | ||
| 740 | =head2 Alternative syntax | |
| 741 | ||
| 742 | Perl 6 will provide a built-in switch statement with essentially the | |
| 743 | same semantics as those offered by Switch.pm, but with a different | |
| 744 | pair of keywords. In Perl 6 C<switch> will be spelled C<given>, and | |
| 745 | C<case> will be pronounced C<when>. In addition, the C<when> statement | |
| 746 | will not require switch or case values to be parenthesized. | |
| 747 | ||
| 748 | This future syntax is also (largely) available via the Switch.pm module, by | |
| 749 | importing it with the argument C<"Perl6">. For example: | |
| 750 | ||
| 751 | use Switch 'Perl6'; | |
| 752 | ||
| 753 | given ($val) { | |
| 754 | when 1 { handle_num_1(); } | |
| 755 | when ($str1) { handle_str_1(); } | |
| 756 | when [0..9] { handle_num_any(); last } | |
| 757 | when /\d/ { handle_dig_any(); } | |
| 758 | when /.*/ { handle_str_any(); } | |
| 759 | } | |
| 760 | ||
| 761 | Note that scalars still need to be parenthesized, since they would be | |
| 762 | ambiguous in Perl 5. | |
| 763 | ||
| 764 | Note too that you can mix and match both syntaxes by importing the module | |
| 765 | with: | |
| 766 | ||
| 767 | use Switch 'Perl5', 'Perl6'; | |
| 768 | ||
| 769 | ||
| 770 | =head2 Higher-order Operations | |
| 771 | ||
| 772 | One situation in which C<switch> and C<case> do not provide a good | |
| 773 | substitute for a cascaded C<if>, is where a switch value needs to | |
| 774 | be tested against a series of conditions. For example: | |
| 775 | ||
| 776 | sub beverage { | |
| 777 | switch (shift) { | |
| 778 | ||
| 779 | case sub { $_[0] < 10 } { return 'milk' } | |
| 780 | case sub { $_[0] < 20 } { return 'coke' } | |
| 781 | case sub { $_[0] < 30 } { return 'beer' } | |
| 782 | case sub { $_[0] < 40 } { return 'wine' } | |
| 783 | case sub { $_[0] < 50 } { return 'malt' } | |
| 784 | case sub { $_[0] < 60 } { return 'Moet' } | |
| 785 | else { return 'milk' } | |
| 786 | } | |
| 787 | } | |
| 788 | ||
| 789 | The need to specify each condition as a subroutine block is tiresome. To | |
| 790 | overcome this, when importing Switch.pm, a special "placeholder" | |
| 791 | subroutine named C<__> [sic] may also be imported. This subroutine | |
| 792 | converts (almost) any expression in which it appears to a reference to a | |
| 793 | higher-order function. That is, the expression: | |
| 794 | ||
| 795 | use Switch '__'; | |
| 796 | ||
| 797 | __ < 2 + __ | |
| 798 | ||
| 799 | is equivalent to: | |
| 800 | ||
| 801 | sub { $_[0] < 2 + $_[1] } | |
| 802 | ||
| 803 | With C<__>, the previous ugly case statements can be rewritten: | |
| 804 | ||
| 805 | case __ < 10 { return 'milk' } | |
| 806 | case __ < 20 { return 'coke' } | |
| 807 | case __ < 30 { return 'beer' } | |
| 808 | case __ < 40 { return 'wine' } | |
| 809 | case __ < 50 { return 'malt' } | |
| 810 | case __ < 60 { return 'Moet' } | |
| 811 | else { return 'milk' } | |
| 812 | ||
| 813 | The C<__> subroutine makes extensive use of operator overloading to | |
| 814 | perform its magic. All operations involving __ are overloaded to | |
| 815 | produce an anonymous subroutine that implements a lazy version | |
| 816 | of the original operation. | |
| 817 | ||
| 818 | The only problem is that operator overloading does not allow the | |
| 819 | boolean operators C<&&> and C<||> to be overloaded. So a case statement | |
| 820 | like this: | |
| 821 | ||
| 822 | case 0 <= __ && __ < 10 { return 'digit' } | |
| 823 | ||
| 824 | doesn't act as expected, because when it is | |
| 825 | executed, it constructs two higher order subroutines | |
| 826 | and then treats the two resulting references as arguments to C<&&>: | |
| 827 | ||
| 828 | sub { 0 <= $_[0] } && sub { $_[0] < 10 } | |
| 829 | ||
| 830 | This boolean expression is inevitably true, since both references are | |
| 831 | non-false. Fortunately, the overloaded C<'bool'> operator catches this | |
| 832 | situation and flags it as a error. | |
| 833 | ||
| 834 | =head1 DEPENDENCIES | |
| 835 | ||
| 836 | The module is implemented using Filter::Util::Call and Text::Balanced | |
| 837 | and requires both these modules to be installed. | |
| 838 | ||
| 839 | =head1 AUTHOR | |
| 840 | ||
| 841 | Damian Conway (damian@conway.org) | |
| 842 | ||
| 843 | =head1 BUGS | |
| 844 | ||
| 845 | There are undoubtedly serious bugs lurking somewhere in code this funky :-) | |
| 846 | Bug reports and other feedback are most welcome. | |
| 847 | ||
| 848 | =head1 LIMITATION | |
| 849 | ||
| 850 | Due to the heuristic nature of Switch.pm's source parsing, the presence | |
| 851 | of regexes specified with raw C<?...?> delimiters may cause mysterious | |
| 852 | errors. The workaround is to use C<m?...?> instead. | |
| 853 | ||
| 854 | =head1 COPYRIGHT | |
| 855 | ||
| 856 | Copyright (c) 1997-2001, Damian Conway. All Rights Reserved. | |
| 857 | This module is free software. It may be used, redistributed | |
| 858 | and/or modified under the same terms as Perl itself. |