ANN: HStringTemplate 0.3.1

This release of HStringTemplate (up now at Hackage) fixes a number of bugs pointed out to me by its small but growing user base (thanks, cinema, elliottt!) ranging from the minor (a particular two-level iteration pattern wasn’t working properly) to the truly irritating (poor handling of file groups). It’s still unfortunately skimpy on the docs, outside of the haddocks and the main StringTemplate grammar documentation at (although the examples from my new project [coming soon!] should also prove helpful). However, it does have a set of very nice and handy new features for development.

* renderf, a function similar in spirit to printf, that takes an arbitrary number of heterogeneous (String, value) tuples as arguments. This should cut down considerably on long setAttribute chains. Additionally, with custom instances (not, I’ll grant, trivial to write) it can be used to declaratively chain together strings of attribute retrieval functions in arbitrary monads, as in the above code example from hvac.

* dumpAttribs, a function/template that prints out the tree of the entire attribute environment a template is operating in — extremely handy for development.

* nullGroup, also for use in development, a simple way to display more information about templates that can’t be found. Error messages in usafeVolatileDirectoryGroup have also been significantly improved.

* getStringTemplate’, a version of getStringTemplate guaranteed not to be inlined. While the optimizer will still sometimes rearrange code such that a volatile group is not updated properly, this at least helps remedy the situation (I think).

* Some minor changes: For grammar reasons, dots have been removed from template names — however, underscores and slashes are now available. Additionally, there’s a much improved logic for which aspects of a local environment are overridden and preserved when a template is called from another.


  1. discordian said

    Hmm. Does this work like it should? (I don’t know stringtemplate, but I’d still expect the separator there..)

    Testing> putStrLn.toString.setAttribute “xs” [1..10] $ newSTMP “test: $xs:{n|#$n$#};separator=\”-\”$”

    test: #1##2##3##4##5##6##7##8##9##10#

  2. sclv said

    I should write this up in a more detailed way, but this is a pretty common gotcha. The separator is inserted in between values when a list is printed. a series of anonymous template subapplications do not constitute a list — think of it as a concatMap rather than a map. The first and rest functions (conceptually head and tail) can be used to apply different templates to different portions of the list to get the effect you want.

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