Pure Go string "interpolation/evaluation" package available?

[Art Mellor]

I'm in need of a lightweight, pure Go package to do simple string evaluation/interpolation similar to what you can do in bash (but I don't want to call out to an external shell).

e.g. in bash you can do:

foo=3

bar=5

echo "Thing-$(( foo + bar * 3 ))"

Thing-18

I'd like some way to set var names in an environment and evaluate strings with some simple language embedded that would do simple substitution and arithmetic. I should be able to get by with =,+,-,*,/ as operators.

I've searched around a bit, but I think I may not be using the right keywords.

Pointers to anything like this that you know of would be greatly appreciated.

[Rui Ueyama]

Are "foo" and "bar" in your example all environment variable? If so, it's technically doable, although I don't think there's existing code for doing that.

If these variables are local variables in Go, it's not doable, because even if you use reflection you cannot access local variables by name.

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[Aston Motes]

Here's one templating library that does what you're looking for:

https://www.florian-schlachter.de/post/pongo2/

I can't vouch for the library too much as I haven't really used it, but it seems to work for your example. (http://play.golang.org/p/KXqYIqmpIW) I'm sure there are others...

On Wed, Aug 27, 2014 at 1:42 PM, Art Mellor <art.ze...@gmail.com> wrote:

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[Art Mellor]

By environment variable I'm speaking generically, not specifically shell environment. I mean an environment specific to a session or something. I.e. state can be maintained across individual string evaluations.

[Art Mellor]

Thanks! I'll check that out.

[sande...@gmail.com]

For runtime templating you can use:

http://golang.org/pkg/text/template/#example_Template

Just made a little compile time tool that might be useful:

https://github.com/sanderhahn/gotemplate

It compiles erb style templates into pure go functions.

Best regards,

Sander Hahn