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digitalmars.D.learn - Type trait alias parameters being either a string or a type

reply =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:
As a follow up to

http://forum.dlang.org/thread/waxtzdemkuzvqdwilulj forum.dlang.org#post-waxtzdemkuzvqdwilulj:40forum.dlang.org

I'm trying to create a type trait isIndexableBy at

https://github.com/nordlow/justd/blob/isIndexableBy-problem/typecons_ex.d

DMD complains

typecons_ex.d(78,30): Error: template instance isUnsigned!("I") 
does not match template declaration isUnsigned(T)
typecons_ex.d(79,30): Error: template instance isIndex_!("I") 
does not match template declaration isIndex_(I)
typecons_ex.d(91,35): Error: template instance 
typecons_ex.isIndexType!("I") error instantiating
typecons_ex.d(95,19):        instantiated from here: 
isIndexableBy!(int[], "I")
typecons_ex.d(96,19): Error: template instance 
isIndexableBy!(int[3], ubyte) does not match template declaration 
isIndexableBy(R, alias I)
typecons_ex.d(183,20): Error: template typecons_ex.indexedBy 
cannot deduce function from argument types !(ubyte)(int[3]), 
candidates are:
typecons_ex.d(156,6):        typecons_ex.indexedBy(alias I, R)(R 
range) if (isIndexableBy!(R, I))

How do I make the call isUnsigned!I return false instead of error 
when I is a CT string literal?

Is my design sane ("D-ish")?
Apr 15 2015
parent =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:
On Wednesday, 15 April 2015 at 08:42:31 UTC, Nordlöw wrote:

 As a follow up to

 http://forum.dlang.org/thread/waxtzdemkuzvqdwilulj forum.dlang.org#post-waxtzdemkuzvqdwilulj:40forum.dlang.org

 I'm trying to create a type trait isIndexableBy at

 https://github.com/nordlow/justd/blob/isIndexableBy-problem/typecons_ex.d

 DMD complains

 typecons_ex.d(78,30): Error: template instance isUnsigned!("I") 
 does not match template declaration isUnsigned(T)
 typecons_ex.d(79,30): Error: template instance isIndex_!("I") 
 does not match template declaration isIndex_(I)
 typecons_ex.d(91,35): Error: template instance 
 typecons_ex.isIndexType!("I") error instantiating
 typecons_ex.d(95,19):        instantiated from here: 
 isIndexableBy!(int[], "I")
 typecons_ex.d(96,19): Error: template instance 
 isIndexableBy!(int[3], ubyte) does not match template 
 declaration isIndexableBy(R, alias I)
 typecons_ex.d(183,20): Error: template typecons_ex.indexedBy 
 cannot deduce function from argument types !(ubyte)(int[3]), 
 candidates are:
 typecons_ex.d(156,6):        typecons_ex.indexedBy(alias I, 
 R)(R range) if (isIndexableBy!(R, I))

 How do I make the call isUnsigned!I return false instead of 
 error when I is a CT string literal?

 Is my design sane ("D-ish")?


I managed to make it all work at

https://github.com/nordlow/justd/blob/master/typecons_ex.d#L114

by using two separate definitions of IndexedBy.
Not pretty but works for now.

See
http://forum.dlang.org/thread/waxtzdemkuzvqdwilulj forum.dlang.org#post-cirmlonzdhcryinyeyap:40forum.dlang.org

for follow-up posts.
Apr 15 2015