[TW5] Problem with macros and default values

[FrD]

Hi,

Still exploring macros and default values.
I've got a problem in a macro calling a second macro. The first macro has some arguments with default values.

Here's an MTC.
Create a tiddler (say TestMacros) with a field "foo" with value "bar".
Put this code in the tiddler :

\define testmacro1(alpha:{{!!title}} beta gamma:{{!!foo}})
<<testmacro2 $alpha$ $beta$ $gamma$>>
\end

\define testmacro2(alpha beta gamma)
alpha = $alpha$
<br>
beta = $beta$
<br>
gamma = $gamma$
\end

<<testmacro1>>

The result is :

alpha = TestMacros
beta = bar
gamma =

Seems to me that beta should'nt hold any value and gamma should hold "bar" as its value.
Could someone explain this behaviour ?

Thanks

FrD

[Jeremy Ruston]

Hi FrD

There are a couple of things going on:

* Parameters in a macro definition are separated with commas. It is unfortunate that this is different than the white space separator used when invoking macros

* In your example, the macro invocation of testmacro2 is unpacking to <<textmacro2 {{!!title}} {{!!foo}}>>. The missing value for the beta parameter comes out blank, causing the value you've specified with $gamma$ to be passed as the parameter "beta" to testmacro2. The workaround is to use named parameters and quotes:

Here's a corrected version:

\define testmacro1(alpha:"{{!!title}}",beta,gamma:"{{!!foo}}")

<<testmacro2 alpha:"""$alpha$""" beta:"""$beta$""" gamma:"""$gamma$""">>

\end

\define testmacro2(alpha,beta,gamma)

alpha = $alpha$

<br>

beta = $beta$

<br>

gamma = $gamma$

\end

<<testmacro1>>

Best wishes

Jeremy

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[FrD]

Hi Jeremy,

Thanks for the quick answer !
I did'nt know these details.
I think the documentation on tiddlywiki.com should be updated : the example in the tiddler "Macro Definitions in WikiText" doesn't use commas to separate the parameters.

FrD

[Jeremy Ruston]

Hi FrD

Thanks for the quick answer !
I did'nt know these details.
I think the documentation on tiddlywiki.com should be updated : the example in the tiddler "Macro Definitions in WikiText" doesn't use commas to separate the parameters.

Oops, you're quite right, or rather my past self was correct: macro definitions can use spaces or commas to separate parameters. As the documentation says: "The parameter separator (sep) is any sequence of characters that does not match a param-name. Among other things, this includes commas, spaces and linefeeds":

http://tiddlywiki.com/Macro%20Definition%20Syntax

Best wishes

Jeremy.

 

FrD

Le lundi 28 septembre 2015 19:20:38 UTC+2, Jeremy Ruston a écrit :

Hi FrD

There are a couple of things going on:

* Parameters in a macro definition are separated with commas. It is unfortunate that this is different than the white space separator used when invoking macros

* In your example, the macro invocation of testmacro2 is unpacking to <<textmacro2 {{!!title}} {{!!foo}}>>. The missing value for the beta parameter comes out blank, causing the value you've specified with $gamma$ to be passed as the parameter "beta" to testmacro2. The workaround is to use named parameters and quotes:

Here's a corrected version:

\define testmacro1(alpha:"{{!!title}}",beta,gamma:"{{!!foo}}")

<<testmacro2 alpha:"""$alpha$""" beta:"""$beta$""" gamma:"""$gamma$""">>

\end

\define testmacro2(alpha,beta,gamma)

alpha = $alpha$

<br>

beta = $beta$

<br>

gamma = $gamma$

\end

<<testmacro1>>

Best wishes

Jeremy