How to return range constructs?

[Robin]

Hiho,

I have made matrix a struct for a better performance and since 
everybody here on the forums was complaining about that it should 
be a struct type.

When I uncomment the currently commented assertion I get linking 
errors. (these strange and nearly unreadable error messages.)

Here is a part of them:
ColumnVectorForwardRange.o: In function 
`_D6neoLab4core6Matrix13__T6MatrixTdZ6Matrix6__ctorMFNaNbNcxmxmxbZS6neoLab4core6Matrix13__T6MatrixTdZ6Matrix':
neoLab/core/Matrix.d:(.text._D6neoLab4core6Matrix13__T6MatrixTdZ6Matrix6__ctorMFNaNbNcxmxmxbZS6neoLab4core6Matrix13__T6MatrixTdZ6Matrix+0x31): 
undefined reference to 
`_D6neoLab4core9Dimension9Dimension6__ctorMFNaNbNcxmxmZS6neoLab4core9Dimension9Dimension'
ColumnVectorForwardRange.o: In function

... many many many lines of error messages ...

ColumnVectorForwardRange.o: In function 
`_D6neoLab4core6Matrix13__T6MatrixTdZ6Matrix6randomFxmxmdddZS6neoLab4core6Matrix13__T6MatrixTdZ6Matrix':
neoLab/core/Matrix.d:(.text._D6neoLab4core6Matrix13__T6MatrixTdZ6Matrix6randomFxmxmdddZS6neoLab4core6Matrix13__T6MatrixTdZ6Matrix+0x145): 
undefined reference to 
`_D6neoLab4core9Dimension9Dimension4sizeMxFNaNbNdZm'
collect2: error: ld returned 1 exit status
--- errorlevel 1

Robin