Scanning

⁠

The Scanner has two jobs:

remove comments

produce character stream

Removing Comments

The scanner has to iterate over each line, and implement a simple algorithm to ignore the current line if it is a comment or part of a multiline comment.

This is what Scanner.stripComments does:

String stripComments(String source) {

List<String> lines = [];

bool inMultilineComment = false;

source.split("\n").forEach((String line) {

String cleanLine = line.trim();

if (cleanLine.length > 1) {

if (cleanLine[0] == '/') {

if (cleanLine[1] == '/' || cleanLine[1] == '|') {

} else if (cleanLine[1] == '*') {

inMultilineComment = true;

}

} else if (cleanLine[0] == '*' && cleanLine[1] == '/') {

inMultilineComment = false;

} else {

!inMultilineComment ? lines.add(line) : null;

}

} else {

!inMultilineComment ? lines.add(line) : null;

}

});

return lines.join('\n');

}

It adds each line to the cleaned source only if it is not a comment or part of one.

Character Stream

This step is basically taking this:

var myVar = 10;

And turning it into this:

[v, a, r, , m, y, V, a, r, , =, , 1, 0, ;]

The list of characters above is known as a character stream. I don’t suppose we need to see how Insidion implements this because it’s as simple as source.split(’’) .

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