Parsing code

[drekka]

Hi, I'm looking at Patterns to try and pass strings that contain small chunks of source code. I'm trying to work out if I can get it to pass a string that looks like this:

x = "abc"

The part I'm troubled with is the string declaration and I'm not sure if Patterns can handle a pattern where I need a double quote following by any number of characters and ending with a second double quote.

The value "abc" seems pretty straight forwards. But what if it contains a double quote. i.e "a\"bc".

[wilhuff]

A typical way you approach this problem (for nearly every parsing system) is to define a quoted string as consisting of a zero or more runs where each run is either

• One or more characters other than " or \\
• An escape sequence where you explicitly enumerate the escaped characters you accept, including \"

Something like:

let quotedStringChars = Capture(name: "chars", (!OneOf("\\\"") • OneOf(any))+)
let escapeSequence = "\\" • Capture(name: "escape", OneOf("bnrtv\""))
let quotedStringContent = quotedStringChars / escapeSequence
let quotedString = "\"" • quotedStringContent* • "\""

Handling this requires combining the resulting series of captures, mapping the escape character code to its equivalent (e.g. "n" maps to "\n") before doing anything with the Match.