In ant given a true or false property how can I conditionally define a macrodef - ant

Question

I have a situation in a build file where I want two OS dependent versions of a macrodef and want to select which one gets "compiled" based on a flag that is true or false.
<condition property="use.windows.macros" value=true else=false
<os family="windows" />
</condition>
Pseudocode
if(use.windows.macrodef)
<macrodef aMacro
... windows version
</macrodef>
else
<macrodef aMacro
... non windows version
</macrodef>
endif
how does one do this sort of thing with the basic out of the box ant xml nodes?

Answer 1

Why do you want two versions of macro? You can use only one (assuming you have ant version >= 1.9.3)
<project xmlns:if="ant:if" xmlns:unless="ant:unless">
<condition property="os.windows">
<os family="windows"/>
</condition>
<condition property="os.linux">
<os family="unix" name="linux" />
</condition>
<macrodef name="sayHello">
<sequential>
<sequential if:set="os.windows">
<echo message="hello from windows" />
</sequential>
<sequential if:set="os.linux">
<echo message="hello from linux" />
</sequential>
</sequential>
</macrodef>
<sayHello />
</project>

Answer 2

Ok - yes a synthesis of the prior partial answer and my work on it but this is what I ended up with as a structure.
I have to create two macros - the first creates the others based on the flags.
I'm not sure how this jibes with canonical ant but it does the job I need done and is easy for someone to see what is meant.
<condition property="os.windows">
<os family="windows"/>
</condition>
<condition property="os.linux">
<os family="unix" name="linux" />
</condition>
<macrodef name="createOsMacros">
<sequential if:set="os.windows">
<macrodef name="doOsMacro">
<attribute name="printstring" default="windows string"/>
<sequential>
<echo message="#{printstring}" />
</sequential>
</macrodef>
</sequential>
<sequential if:set="os.linux">
<macrodef name="doOsMacro">
<attribute name="printstring" default="unix string"/>
<sequential>
<echo message="#{printstring}" />
</sequential>
</macrodef>
</sequential>
</macrodef>
<createOsMacros />
<doOsMacro />