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December 19, 2020 14:13
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Advent of Code day 18 solultion in Raku #rakulang
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grammar Expression { | |
token integer { \d+ } | |
proto token operator { <*> } | |
token operator:sym<+> { <sym> } | |
token operator:sym<*> { <sym> } | |
rule term { <integer> | <parens> } | |
rule parens { '(' ~ ')' <expression> } | |
rule expression { <term> + % <operator> } | |
token TOP { <.ws> <expression> } | |
} | |
class ExpressionAction { | |
method integer($/) { make $/.Int } | |
method operator:sym<+>($/) { make &[+] } | |
method operator:sym<*>($/) { make &[*] } | |
method term($/) { make $/.caps[0].value.made } | |
method parens($/) { make $<expression>.made } | |
method expression($/) { make [ $/.caps>>.value>>.made ] } | |
method TOP($/) { make $<expression>.made } | |
} | |
multi eval-ast(Int $x) { $x } | |
multi eval-ast(@ast) { | |
my $value = eval-ast(@ast.shift); | |
while @ast { | |
my &operator = @ast.shift; | |
my \rhs = eval-ast @ast.shift; | |
$value = operator($value, rhs); | |
} | |
return $value; | |
} | |
sub expr(Str $input) { | |
my $match = Expression.parse($input, :actions(ExpressionAction)); | |
die "Invalid input <$input>\n" unless $match; | |
return eval-ast($match.made); | |
} | |
multi MAIN('test') { | |
use Test; | |
plan 3; | |
is expr('123'), 123, 'single-integer expression'; | |
is expr('1 + 2 * 3 + 4 * 5 + 6'), 71, 'left to right, no parenthesis'; | |
is expr('1 + (2 * 3) + (4 * (5 + 6))'), 51, 'Parenthesis expression' | |
} | |
multi MAIN() { | |
say [+] $*IN.lines.map: &expr; | |
} |
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