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Zane, Angus, thanks for your input!

This functional based syntax is consisted for dev use. The trouble is it ITSELF needs to be delimited. Without pissing off the users :) Consider two key usage:  input parameters and shorthand syntax for action input. That’s why we are looking for two-char symmetric (opening + closing) delimiters. 

task_with_full_syntax_input:
  action: std.ssh
  input: 
     cmd = awk '{ print "<% $.my_var %>" }' /etc/passwd

task_with_shorthand_action_input:
  action: std.ssh cmd="awk '{ print \”<% $.my_var %>\" }' /etc/passwd”

using function-like we still will have to do 
  action: std.ssh cmd=“awk '{ print \”<% yaql {$.my_var} %>\" }' /etc/passwd”
that only adds confusion IMO. 

The full set of usages for YAQL in DSL is here: https://etherpad.openstack.org/p/mistral-YAQL-delimiters

DZ. 

On Feb 18, 2015, at 7:22 AM, Zane Bitter <zbitter at redhat.com> wrote:

> On 16/02/15 16:06, Dmitri Zimine wrote:
>> 2) Use functions, like Heat HOT or TOSCA:
>> 
>> HOT templates and TOSCA doesn’t seem to have a concept of typed
>> variables to borrow from (please correct me if I missed it). But they
>> have functions: function: { function_name: {foo: [parameter1, parameter
>> 2], bar:"xxx”}}. Applied to Mistral, it would look like:
>> 
>>     publish:
>>      - bool_var: { yaql: “1+1+$.my.var < 100” }
>> 
>> Not bad, but currently rejected as it reads worse than delimiter-based
>> syntax, especially in simplified one-line action invocation.
> 
> Note that you don't actually need the quotes there, so this would be equivalent:
> 
>    publish:
>     - bool_var: {yaql: 1+1+$.my.var < 100}
> 
> FWIW I am partial to this or to Renat's p7 suggestion:
> 
>    publish:
>     - bool_var: yaql{1+1+$.my.var < 100}
> 
> Both offer the flexibility to introduce new syntax in the future without breaking backwards compatibility.
> 
> cheers,
> Zane.
> 
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