Recursive descent parser generator: Difference between revisions
Rename Perl 6 -> Raku, alphabetize, minor clean-up
(added Perl 6 programming solution) |
Thundergnat (talk | contribs) (Rename Perl 6 -> Raku, alphabetize, minor clean-up) |
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└── return %4
)))
</pre>▼
=={{header|Perl 6}}==▼
Instead of writing a full-blown generator, it is possible to solve the task partly by making use of the built-in optimizer and study the relevant AST output▼
<pre>▼
perl6 --target=optimize -e 'no strict; say ($one + $two) * $three - $four * $five' | tail -11▼
- QAST::Op(callstatic &say) <sunk> :statement_id<2> say ($one + $two) * $three - $four * $five▼
- QAST::Op(callstatic &infix:<->) <wanted> -▼
- QAST::Op(callstatic &infix:<*>) <wanted> *▼
- QAST::Op(callstatic &infix:<+>) <wanted> :statement_id<3> +▼
- QAST::Var(local __lowered_lex_5) <wanted> $one▼
- QAST::Var(local __lowered_lex_4) <wanted> $two▼
- QAST::Var(local __lowered_lex_3) <wanted> $three▼
- QAST::Op(callstatic &infix:<*>) <wanted> *▼
- QAST::Var(local __lowered_lex_2) <wanted> $four▼
- QAST::Var(local __lowered_lex_1) <wanted> $five▼
- QAST::WVal(Nil)▼
</pre>▼
As you can see by examining the nested tree, the calculations are done as follows (expressed using a postfix notation)▼
<pre>▼
one two + three * four five * -▼
</pre>
Line 769 ⟶ 748:
_0003 = four * five
_0004 = _0002 - _0003
▲</pre>
(formerly Perl 6)
▲Instead of writing a full-blown generator, it is possible to solve the task partly by making use of the built-in optimizer and study the relevant AST output
▲<pre>
▲perl6 --target=optimize -e 'no strict; say ($one + $two) * $three - $four * $five' | tail -11
▲ - QAST::Op(callstatic &say) <sunk> :statement_id<2> say ($one + $two) * $three - $four * $five
▲ - QAST::Op(callstatic &infix:<->) <wanted> -
▲ - QAST::Op(callstatic &infix:<*>) <wanted> *
▲ - QAST::Op(callstatic &infix:<+>) <wanted> :statement_id<3> +
▲ - QAST::Var(local __lowered_lex_5) <wanted> $one
▲ - QAST::Var(local __lowered_lex_4) <wanted> $two
▲ - QAST::Var(local __lowered_lex_3) <wanted> $three
▲ - QAST::Op(callstatic &infix:<*>) <wanted> *
▲ - QAST::Var(local __lowered_lex_2) <wanted> $four
▲ - QAST::Var(local __lowered_lex_1) <wanted> $five
▲ - QAST::WVal(Nil)
▲</pre>
▲As you can see by examining the nested tree, the calculations are done as follows (expressed using a postfix notation)
▲<pre>
▲one two + three * four five * -
</pre>
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