Capture and execute multiline code and incorporate result in raku

Question

This is a markdown document example.md I have:

## New language

Raku is a new language different from Perl.

## what does it offer
+ Object-oriented programming including generics, roles and multiple dispatch
+ Functional programming primitives, lazy and eager list evaluation, junctions, autothreading and hyperoperators (vector operators)
+ Parallelism, concurrency, and asynchrony including multi-core support
+ Definable grammars for pattern matching and generalized string processing
+ Optional and gradual typing



This code will be evaluated.


```{raku evaluate=TRUE}
4/5
```



Rakudo is a compiler for raku programming language. Install it and you're all set to run raku programs!

This code will be evaluated.

```{raku evaluate=TRUE}
say "this is promising";
say $*CWD;
```



This code will **not** be evaluated.


```{raku evaluate=FALSE}
say "Hello world";
```

which I want to convert into example.md as shown below with the code and output within it.

## New language

Raku is a new language different from Perl.

## what does it offer
+ Object-oriented programming including generics, roles and multiple dispatch
+ Functional programming primitives, lazy and eager list evaluation, junctions, autothreading and hyperoperators (vector operators)
+ Parallelism, concurrency, and asynchrony including multi-core support
+ Definable grammars for pattern matching and generalized string processing
+ Optional and gradual typing



This code will be evaluated.

Code:
```{raku evaluate=TRUE}
4/5
```

Output:
```
0.8
```

Rakudo is a compiler for raku programming language. Install it and you're all set to run raku programs!

This code will be evaluated.

Code:
```{raku evaluate=TRUE}
say "this is promising";
say $*CWD;
```

Output:
```
this is promising
"C:\Users\suman".IO
```

This code will **not** be evaluated.

Code:
```{raku evaluate=FALSE}
say "Hello world";
```

---

What I want to accomplish is:

• capture the code between backticks{raku evaluate} and backticks
• execute the code if evaluate is TRUE
• insert the code and output back into the document

---

What I tried to do:

1. Capture multiline code and evaluate expression

my $array= 'example.md'.IO.slurp;

#multiline capture code chunk and evaluate separately
if $array~~/\`\`\`\{raku (.*)\}(.*)\`\`\`/ {
    #the first capture $0 will be evaluate
    if $0~~"TRUE"{
        #execute second capture which is code chunk which is captured in $1
        }else {
       # don't execute code
        };
};

2. create a temp.p6 file and write code chunk $1 from above into it

my $fh="temp.p6".IO.spurt: $1;

3. execute the chunk if $0 is TRUE

my $output= q:x/raku temp.p6/ if $0==TRUE

4. integrate all this into final example.md while we create intermediate example_new.md

my $fh-out = open "example_new.md", :w; # Create a new file

# Print out next file, line by line
for "$file.tex".IO.lines -> $line {

    # write output of code to example_new.md

}
$fh-out.close;

# copy
my $io = IO::Path.new("example_new.md");
$io.copy("example.md");

# clean up
unlink("example.md");

# move
$io.rename("example.md");

I am stuck in the first step. Any help?

Answer 1

There are two ways to execute the code and capture the output:

• You can write it to a tempfile and use my $result = qqx{perl6 $filename} to spawn a separate process
• You can execute the code in the same interpreter using EVAL, and use IO::Capture::Simple to capture STDOUT:

my $re = regex {
    ^^ # logical newline
    '```{perl6 evaluate=' (TRUE|FALSE) '}'
    $<code>=(.*?)
    '```'
}

for $input.match(:global, $re) -> $match {
    if $match[0] eq 'TRUE' {
        use IO::Capture::Simple;
        my $result = capture_stdout {
            use MONKEY-SEE-NO-EVAL;
            EVAL $match<code>;
        }
        # use $result now
    }
}

Now you just need to switch from match to subst and return the value from that block that you want to substitute in, and then you're done.

I hope this gives you some idea how to proceed.