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Reini Urbanrurban
Reini Urban
authored and
rurban
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exact_arith: implement it
Promote on overflow to bigint/num, and not to NV. This is a new lexical user-pragma to use exact arithmetic without loosing precision on all builtin arithmetic ops. As in perl6. It is of course a bit slower than without. Closes #21.
1 parent 6c02d8a commit 22b61d6

17 files changed

+308
-43
lines changed

‎Configure

+28
Original file line numberDiff line numberDiff line change
@@ -1424,6 +1424,7 @@ CONFIG=''
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usecperl=''
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fake_signatures=''
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usenamedanoncv=''
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useexactarith=''
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: Detect odd OSs
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define='define'
@@ -7584,6 +7585,32 @@ $define)
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;;
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esac
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case "$useexactarith" in
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$define|true|[yY]*) dflt='y' ;;
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*) dflt='n' ;;
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esac
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cat <<EOM
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Would you like to build Perl so that every builtin arithmetic overflow
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does not promote to internal fast double/long double numbers but
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instead to slow and precise bigint? So that exact_arith is enabled by default.
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If this doesn't make any sense to you, just accept the default '$dflt'.
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EOM
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rp='Use exact arith, overflow to bigint as in perl6?'
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. ./myread
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case "$ans" in
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y|Y) val="$define" ;;
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*) val="$undef" ;;
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esac
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set useexactarith
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eval $setvar
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case "$useexactarith" in
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$define)
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echo "exact_arith selected." >&4
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;;
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esac
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case "$usecperl" in
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$define) usecperl='define'
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echo "cperl variant selected." >&4
@@ -25924,6 +25951,7 @@ usecrosscompile='$usecrosscompile'
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usedevel='$usedevel'
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usedl='$usedl'
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usedtrace='$usedtrace'
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useexactarith='$useexactarith'
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usefaststdio='$usefaststdio'
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useffi='$useffi'
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useithreads='$useithreads'

‎MANIFEST

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Original file line numberDiff line numberDiff line change
@@ -5690,6 +5690,8 @@ lib/dumpvar.pl A variable dumper
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lib/dumpvar.t A variable dumper tester
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lib/English.pm Readable aliases for short variables
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lib/English.t See if English works
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lib/exact_arith.pm Pragma to set exact arithmetic as in perl6
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lib/exact_arith.t See if use exact_arith works
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lib/ExtUtils/Embed.pm Utilities for embedding Perl in C programs
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lib/ExtUtils/t/Embed.t See if ExtUtils::Embed and embedding works
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lib/ExtUtils/typemap Extension interface types

‎Porting/Maintainers.pl

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@@ -1732,6 +1732,7 @@ package Maintainers;
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lib/DBM_Filter/
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lib/DirHandle.{pm,t}
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lib/English.{pm,t}
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lib/exact_arith.{pm,t}
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lib/ExtUtils/Embed.pm
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lib/ExtUtils/XSSymSet.pm
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lib/ExtUtils/t/Embed.t

‎config_h.SH

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Original file line numberDiff line numberDiff line change
@@ -5488,6 +5488,14 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
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#$usesafehashiter USE_SAFE_HASHITER /**/
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#endif
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/* USE_EXACT_ARITH:
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* This symbol, if defined, indicates that Perl uses exact_arith as default.
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*/
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#define PERL_EXACT_ARITH
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#ifndef USE_EXACT_ARITH
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#$useexactarith USE_EXACT_ARITH /**/
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#endif
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/* PERL_HASH_FUNC_*:
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* This symbol defines the used perl hash function variant.
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* It is set in Configure or via -Dhash_func=, but can be left blank.

‎embed.fnc

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@@ -528,6 +528,7 @@ pR |int |PerlSock_accept_cloexec|int listenfd \
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pR |int |PerlSock_socketpair_cloexec|int domain|int type|int protocol \
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|NN int *pairfd
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#endif
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AMp |void |bigint_arith |NN const char *op|NN SV *const left|NN SV *const right
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#if defined(PERL_IN_DOIO_C)
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s |IO * |openn_setup |NN GV *gv|NN char *mode|NN PerlIO **saveifp \
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|NN PerlIO **saveofp|NN int *savefd \

‎embed.h

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@@ -67,6 +67,7 @@
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#define av_top_index(a) S_av_top_index(aTHX_ a)
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#define av_undef(a) Perl_av_undef(aTHX_ a)
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#define av_unshift(a,b) Perl_av_unshift(aTHX_ a,b)
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#define bigint_arith(a,b,c) Perl_bigint_arith(aTHX_ a,b,c)
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#define block_end(a,b) Perl_block_end(aTHX_ a,b)
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#define block_gimme() Perl_block_gimme(aTHX)
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#define block_start(a) Perl_block_start(aTHX_ a)

‎ext/Config/Config_xs.in

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@@ -1503,6 +1503,7 @@ usecrosscompile, T_INV,0,ALN64I"@@usecrosscompile@@"
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usedevel, T_INV,0,ALN64I"@@usedevel@@"
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usedl, T_INV,0,ALN64I"@@usedl@@"
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usedtrace, T_INV,0,ALN64I"@@usedtrace@@"
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useexactarith, T_INV,0,ALN64I"@@useexactarith@@"
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usefaststdio, T_INV,0,ALN64I"@@usefaststdio@@"
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useffi, T_INV,0,ALN64I"@@useffi@@"
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useithreads, T_INV,0,ALN64I"@@useithreads@@"

‎lib/exact_arith.pm

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@@ -0,0 +1,30 @@
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package exact_arith;
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our $VERSION = '0.01';
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sub unimport { delete $^H{exact_arith}; }
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sub import { $^H{exact_arith} = 1; }
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1;
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__END__
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=head1 NAME
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exact_arith - promote on overflow to bigint/num
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=head1 SYNOPSIS
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use exact_arith;
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print 18446744073709551614 * 2; # => 36893488147419103228, a bigint object
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{ no exact_arith;
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print 18446744073709551614 * 2; # => 3.68934881474191e+19
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}
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=head1 DESCRIPTION
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24+
This is a new lexical user-pragma since cperl5.24 to use exact
25+
arithmetic, without loosing precision on all builtin arithmetic ops.
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As in perl6.
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28+
It is of course a bit slower, than without.
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30+
=cut

‎lib/exact_arith.t

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@@ -0,0 +1,24 @@
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#!./perl -- -*- mode: cperl; cperl-indent-level: 4 -*-
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BEGIN {
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chdir 't' if -d 't';
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@INC = ( '.', '../lib' );
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}
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use strict;
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require '../t/test.pl';
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plan(4);
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$|=1;
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use exact_arith;
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my $n = 18446744073709551614 * 2; # => 36893488147419103228, a bigint object
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is(ref $n, 'bigint');
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is($n, 36893488147419103228);
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{
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no exact_arith;
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my $m = 18446744073709551614 * 2;
22+
is(ref $n, '');
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is($n, 3.68934881474191e+19);
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}

‎perl.c

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@@ -1932,6 +1932,9 @@ S_Internals_V(pTHX_ CV *cv)
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# ifdef PERL_DONT_CREATE_GVSV
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" PERL_DONT_CREATE_GVSV"
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# endif
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# ifdef PERL_EXACT_ARITH
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" PERL_EXACT_ARITH"
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# endif
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# ifdef PERL_EXTERNAL_GLOB
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" PERL_EXTERNAL_GLOB"
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# endif
@@ -2034,6 +2037,9 @@ S_Internals_V(pTHX_ CV *cv)
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# ifdef USE_CPERL
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" USE_CPERL"
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# endif
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# ifdef USE_EXACT_ARITH
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" USE_EXACT_ARITH"
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# endif
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# ifdef USE_FAST_STDIO
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" USE_FAST_STDIO"
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# endif

‎perl.h

+5-3
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@@ -317,9 +317,11 @@
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RX_ENGINE(rx_sv)->dupe(aTHX_ (rx_sv),(param))
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#endif
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320-
321-
322-
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#ifdef PERL_EXACT_ARITH
321+
#define IS_EXACT_ARITH cop_hints_fetch_pvs(PL_curcop, "exact_arith", REFCOUNTED_HE_EXISTS)
322+
#else
323+
#define IS_EXACT_ARITH 0
324+
#endif
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/*
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* Because of backward compatibility reasons the PERL_UNUSED_DECL

‎pod/perlcdelta.pod

+6
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@@ -551,6 +551,12 @@ release manager will have to investigate the situation carefully.)
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552552
=over 4
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554+
=item L<exact_arith> 0.01
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556+
Promote on overflow to bigint/bignum as in perl6, do not loose precision
557+
with all builtin arithmetic operators.
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L<[cperl #21]|https://github.com/perl11/cperl/issues/21>
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=item L<ffi> 0.01c
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ffi helpers and ffi types.

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