#!/usr/bin/perl

use Template::Alloy;
my $ta = Template::Alloy->new;

$ta->_vars->{'func'} = sub { local $" = ', '; "You passed me (@_)" };
$ta->_vars->{'a'}    = 3;
$ta->_vars->{'b'}    = 4;

$ta->define_operator({
    type       => 'left',  # actually associativiy
    precedence => 85,      # same as '+' in $Template::Alloy::OPERATORS table
    symbols    => ['+++'],
    play_sub   => sub { int($_[0]) + int($_[1]) },
});

for my $expr (
    '1 + 2',
    '1 + 2 * 3',
    '(1 + 2) * 3',
    '2.7e+10 * 3.0e-9', # scientific
    'a + b',            # variables
    'func(1 + 2, 3)',   # functions
    '1.2 +++ 3.4 * 2',  # custom ops
    '1 ? 2 : 3',
    'a + (b',
    '3 + 4 foobar',
    ) {
    my $copy = $expr;
    print "--------------------\n";
    print "- expr: $expr\n";
    print "- outp: ".eval{ $ta->play_expr($ta->parse_expr(\$copy)) }."\n";
    if ($@) {
        print "- err : $@\n";
    } else {
        print "- err : Failed to consume entire string\n" if pos $copy != length $expr;
        print "- tree: ".Template::Alloy->dump_parse_expr(\$expr)."\n";
    }
}

##</code><code>##

--------------------
- expr: 1 + 2
- outp: 3
- tree: [[undef, '+', 1, 2], 0]
--------------------
- expr: 1 + 2 * 3
- outp: 7
- tree: [[undef, '+', 1, [[undef, '*', 2, 3], 0]], 0]
--------------------
- expr: (1 + 2) * 3
- outp: 9
- tree: [[undef, '*', [[undef, '+', 1, 2], 0], 3], 0]
--------------------
- expr: 2.7e+10 * 3.0e-9
- outp: 81
- tree: [[undef, '*', 27000000000, '3e-09'], 0]
--------------------
- expr: a + b
- outp: 7
- tree: [[undef, '+', ['a', 0], ['b', 0]], 0]
--------------------
- expr: func(1 + 2, 3)
- outp: You passed me (3, 3)
- tree: ['func', [[[undef, '+', 1, 2], 0], 3]]
--------------------
- expr: 1.2 +++ 3.4 * 2
- outp: 7
- tree: [[undef, '+++', '1.2', [[undef, '*', '3.4', 2], 0]], 0]
--------------------
- expr: 1 ? 2 : 3
- outp: 2
- tree: [[undef, '?', 1, 2, 3], 0]
--------------------
- expr: a + (b
- outp:
- err : parse.missing.paren error - Missing close ) in group (At char 6)
--------------------
- expr: 3 + 4 foobar
- outp: 7
- err : Failed to consume entire string
- tree: [[undef, '+', 3, 4], 0]