Re: [nant-dev] SUMMARY: Expression Syntax

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This is one of the more compelling arguments for me. I'm leaning towards 
option A with {} used everywhere - for clarity and consistency.- and 
ease of syntax highlighting.

Ian
Jaroslaw Kowalski wrote:

>One more thing which I forgot:
>
>Q1 there's a problem where:
>
>B: ${$propertyname} and ${propertyname}
>C: ${${propertyname}} and ${propertyname}
>
>both are legal forms to express a property. Variant A has no such problem.
>
>Jarek
>
>
>----- Original Message ----- 
>From: "Jaroslaw Kowalski" <ja...@zd...>
>To: "Scott Hernandez" <sk...@eo...>;
><nan...@li...>
>Sent: Saturday, December 06, 2003 11:40 AM
>Subject: [nant-dev] SUMMARY: Expression Syntax
>
>
>  
>
>>Hi Scott,
>>
>>As you requested, here's a summary of expression evaluator discussion:
>>
>>Ian, Gert, Martin - can you please correct me if I'm wrong anywhere in the
>>summary.
>>
>>========================================================
>>There are 2 questions:
>>
>>QUESTION 1:
>>How should expressions be written?
>>
>>A) <echo message="aaa" if="${length(propertyname)=3}" />
>>B) <echo message="aaa" if="${length($propertyname)=3}" />
>>C) <echo message="aaa" if="${length(${propertyname})=3}" />
>>
>>Variant A - is clean and compatible with current approach to accessing
>>properties. Properties can still be accessed as ${propertyname}.
>>
>>This may have the following problems:
>>
>>- it may be hard to distinguish between property and function names
>>    
>>
>because
>  
>
>>they only differ by () (Java, C#, C++ also have this problem).
>>- we may no be able to access some properties (like
>>nant.task.cvs-checkout.location) because they contain dashes which cannot
>>    
>>
>be
>  
>
>>distinguished from "minus" operator. "a-b" could either be "a" MINUS "b"
>>    
>>
>or
>  
>
>>a property named "a-b". Fortunately there are only 6 such properties in
>>    
>>
>NAnt
>  
>
>>(so this could be quite easily resolved):
>>
>>nant.tasks.cvs-update
>>nant.tasks.cvs-checkout
>>nant.tasks.delay-sign
>>nant.tasks.cvs-update.location
>>nant.tasks.cvs-checkout.location
>>nant.tasks.delay-sign.location
>>
>>There was a suggestion to disallow such property names and formally define
>>them as:
>>
>>property name => identifier { DOT identifier } *
>>identifier => [a-zA-Z_][a-zA-Z0-9_]*
>>
>>In English:
>>
>>"property name" is a sequence of "identifiers" separated by dots
>>"identifier" starts with a latin letter or an underscore and contains only
>>letters, digits underscores (like in C#, C++, Java, VB, JavaScript...)
>>
>>- we may not be compatible with property names which are numeric. I was
>>    
>>
>told
>  
>
>>that currently a property can be named "1234". There seems to be an
>>agreement that this should be disallowed asap. I suggest that we disallow
>>properties containing dashes in their names at the same time.
>>- one could always use use propertyvalue('propertyname') function to
>>    
>>
>access
>  
>
>>weird-names properties
>>
>>Variant B - prefix properties with '$' - similar to PERL
>>
>>- is still quite clean, yet there are some dollars starting to appear
>>- this solves the first problem (the properties can be distinguished
>>    
>>
>because
>  
>
>>they are prefixed with $)
>>- accessing properties with dashes can still be tricky:
>>
>>$property-name-with-dashes  // access property
>>$property-name-with-dashes(1) // $property-name-with MINUS dashes(1)
>>
>>Variant C - enclose properties in ${...}
>>
>>- it's difficult to read, especially when using proportional font,
>>- it's unambiguous
>>- no problem accessing any property
>>
>>Opinions on Q1:
>>
>>Jarek: A
>>Martin: A
>>Ian: A or B
>>Gert: B or C
>>
>>QUESTION 2:
>>Should we always require ${} (or anything else we use for quoting) to be
>>written around expressions, or should we allow unquoted expressions in
>>    
>>
>some
>  
>
>>places?
>>
>>Variant A (quote all expressions)
>>
>><if test="${length(someproperty)=3}">
>>    ...
>></if>
>>
>><echo message="test" if ="${length(someproperty)=3}" />
>><echo message="test" unless ="${length(someproperty)=3}" />
>>
>>- it's simple
>>- you ALWAYS use quotes around expressions (both embedded in strings and
>>stand-alone)
>>- you can easily spot the expressions in your build file
>>- this may allow for easy implementation of syntax highlighting (actually
>>    
>>
>I
>  
>
>>already did this for VIM)
>>
>>Variant B: allow for unquoted expressions in some places where non-string
>>values are expected:
>>
>>Like "<if test="..." /> <... if="..." /> <... unless="..." />
>>
>><if test="length(someproperty)=3">
>>    ...
>></if>
>><echo message="test" if="length(someproperty)=3" />
>><echo message="test" unless="length(someproperty)=3" />
>>
>>- this is somewhat more readable (less dollars)
>>- it may be hard to find expressions in the build file.
>>- it may not be clear when to use quotes and when not to use them
>>
>>Variant C: skip quotes for <if test="..." /> - keep for everything else
>>
>>- this is implemented in "test1"
>>
>>Opinions on Q2:
>>
>>Jarek: A
>>Martin: A
>>
>>CURRENT STATUS:
>>
>>1. Expression evaluator is in CVS in branch "EE-patches"
>>2. It implements variants: Q1:A and Q2:C
>>
>>A binary release of this is available at
>>
>>http://jaak.sav.net/nant-ee/nant-ee-test1.zip
>>
>>It contains some test cases written as a build file.
>>
>>Jarek
>>
>>
>>
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>
>
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-- 
Ian MacLean, Developer, 
ActiveState, a division of Sophos
http://www.ActiveState.com