in reply to Generic RPN Translator available?
This might form a useful starting point. It seems reasonably accurate, flexible and efficient.
Update: Improved error handling a little and added XLATE option.
Update2: Apparently there is something wrong with this code. Would someone care to tell me what that is?
#! perl slw
use strict;
use List::Util qw[ reduce ]; $a=$b;
our $XLATE = 0;
sub nestedOk{
index( $_[ 0 ], '(' ) <= index( $_[ 0 ], ')' ) and
0 == reduce{
$a + ( $b eq '(' )  ( $b eq ')' )
} 0, split'[^()]*', $_[ 0 ]
}
my $re_var = qr[ [azAZ]\w* ]x;
my $re_subex = qr[ \{\d+\} ]x;
my $re_func = qr[ $re_var $re_subex ]x;
my $re_num = qr[ ? \d+ (?: \. \d+ )? (?: [Ee] [+]? \d+ )? ]x;
my $re_term = qr[ $re_func  $re_subex  $re_var  $re_num ]x;
my $re_op = qr[[,%+*/^]];
my %ops = ( qw[ % MOD + ADD * MULT / DIV ^ POW  SUBT ] );
sub exp2rpn {
my( $exp, $aStack, $aBits ) = @_;
die "Unbalanced parens: '$exp'" unless nestedOk $exp;
{
my( $left, $op, $right, $rest ) = $exp =~ m[
^ ( $re_term )? ( $re_op )? ( $re_term ) ( .* ) $
]x or die "malformed (sub)expression '$exp'";
for ( $left, $right ) {
next unless $_;
if( my( $func, $subex ) = m[^ ( $re_var )? \{ ( \d+ ) \} $
+]x ) {
exp2rpn( $aBits>[ $subex ], $aStack, $aBits );
push @$aStack, $func if $func
}
else{
push( @$aStack, $_ );
}
}
push @$aStack, $XLATE ? $ops{ $op } : $op
if $op and $op ne ',';
$exp = $rest, redo if $rest;
}
return $aStack;
}
sub parseExp {
local $_ = $_[ 0 ];
s[\s+][]g;
my( $bit, @bits ) = 0;
s[\( ( [^()]+ ) \)]{ push @bits, $1; "{${ \( $bit++ ) }}"; }ex
while m[[()]];
my $toplvl = $_;
return @{ exp2rpn $toplvl, [], \@bits };
}
die "No expression given\n" unless @ARGV;
print join', ', parseExp $ARGV[ 0 ];
__END__
P:\test>4233052 "2*(somevar+other) + max(this, that)"
2, somevar, other, +, *, this, that, max, +
P:\test>4233052 "5^((2+x)*sin(p+4)/fred)"
5, 2, x, +, p, 4, +, sin, *, fred, /, ^
P:\test>4233052 "A+(B*CD)/E"
A, B, C, *, D, , +, E, /
P:\test>4233052 "max( a, b, c, d ) * atan( pi*4, 1 )"
a, b, c, d, max, pi, 4, *, 1, atan, *
P:\test>423305 XLATE "5^((2+x)*sin(p+4)/fred)"
5, 2, x, ADD, p, 4, ADD, sin, MULT, fred, DIV, POW
You may need to tweak the named regex at the top to match your definition of variable names, function names and acceptable numeric forms.
Functions are assumed to have fixed numbers of arguments and know how to unstack the correct number. I don't know how (or if) functions with variable numbers of arguments are handle in RPN?
Examine what is said, not who speaks.
Silence betokens consent.
Love the truth but pardon error.
Re^2: Generic RPN Translator available?
by dfaure (Chaplain) on Jan 20, 2005 at 22:22 UTC

I don't know how (or if) functions with variable numbers of arguments are handle in RPN?
As a previous life's HP48 owner, number of arguments is pushed onto the stack after them. Since functions know how to unstack their args, in this case this is a two steps operation
____
HTH, Dominique
My two favorites:
If the only tool you have is a hammer, you will see every problem as a nail. Abraham Maslow
Bien faire, et le faire savoir...
 [reply] 

Update: Looks like I spoke too soon:
"sin(ab)"
yields
sin, a, b
instead of the correct
sin, ab
Hmmm ...
Actually, I was looking for exactly the solution browserUK provided. Outstanding job, browserUK! It even works for nested function calls like
"max(min(a,bc), c, min(df,e) ) * atan( pi*4, 1 )"
which gets transformed to
a, b, c, , min, c, d, f, , e, min, max, pi, 4, *, 1, atan, *
Now, anyone up for a Parse::Descent grammar, just for kicks :) ?
 [reply] [d/l] [select] 

P:\test>423305 XLATE
1+2+3
1, 2, ADD, 3, ADD
a+b+c
a, b, ADD, c, ADD
abc+def+Efg_hij
abc, def, ADD, Efg_hij, ADD
2.0+1e2/0.01E21
2.0, 1e2, ADD, 0.01E21, DIV
max( a, b, c, d ) * atan( pi*4, 1 )
a, b, c, d, 4, max, pi, 4, MULT, 1, 2, atan, MULT
sin( cos( x )  tan( y ) ) + f( g( z ) )
x, cos, y, tan, SUBT, sin, z, g, f, ADD
2*(somevar+other) + max(this, that)
2, somevar, other, ADD, MULT, this, that, 2, max, ADD
A+(B*CD)/E
A, B, C, MULT, D, SUBT, ADD, E, DIV
(a*(b)c^(3.4e2))
a, b, MULT, c, SUBT, 3.4e2, POW
5^((2e3+x)*sin(p+4.0)/fred)
5, 2e3, x, ADD, p, 4.0, ADD, sin, MULT, fred, DIV, POW
sin(a) + sin(ab) + sin( a, b )
a, sin, ab, sin, ADD, a, b, 2, sin, ADD
Func_1( 1, Func_2( Func3( 1* 2 * 3) * aFunc( 3 ) )+FuNc(4,5,6), 2,e,
+10, 2e10 ) +1
1, 1, 2, MULT, 3, MULT, Func3, 3, aFunc, MULT, Func_2, 4, 5,
+6, 3, FuNc, ADD, 2, e, 10, 2e10, 6, Func_1, 1, ADD
Anyone have a ready source of expressions plus their RPN forms? Or a clever way of verifying them?
Examine what is said, not who speaks.
Silence betokens consent.
Love the truth but pardon error.
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P:\test>423305 "max( a, b, c, d ) * atan( pi*4, 1 )"
a, b, c, d, 4, max, pi, 4, *, 1, 2, atan, *
Modified code
Examine what is said, not who speaks.
Silence betokens consent.
Love the truth but pardon error.
 [reply] [d/l] [select] 

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