One thing I noticed is that the parser is hand written. Which is interesting. I always preferred to write my parsers in Yacc and Go actually has Yacc as a built in tool (although know Lex).
Edit: I went through the list someone else posted and only one of the implementations actually has a Yacc grammar file in it.
That said - many languages I dabble in are variants on Forths or Lisps where parsing is easy comparatively.
For posterity, it's moved to https://godoc.org/golang.org/x/tools/cmd/goyacc
Interesting. Did they combine both a lexer and a parser into one tool?
lex,flex, and re2c are typically standalone tools (lexers) that tokenize input, whereas yacc and bison are parsers that parse those tokens into ASTs (usually).
No. They give you an interface definition for the lexer and you can implement the methods however you see fit as long as it matches the interface.
Which I found annoying as there are some tedious parts to writing a lexer as soon as you have a language requiring multi-rune tokens with common prefixes.[1]
Apparently the back story is that go needed a parser generator but they didn't need a lexer so they only built just the one out of necessity.
I read some places that they would welcome pull requests for a lex/flex equivalent.
[1] A `rune` in GoLang is like a `char` in C only it stores multi-byte characters where as in C it is more analogous to a single `byte`
A rune is just an alias for int32. But it's context usually means unicode chars which are indeed multi-byte.
You can still use byte arrays (or "slice" if you're writing idiomatic Go, but that's another tangent again) too though.
Also "byte" in Go is another alias, but for int8. But that shouldn't come as a surprise to anyone :)