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digitalmars.D.learn - Q about template for matching arrays

reply Bill Baxter <dnewsgroup billbaxter.com> writes:
I'd like to write a template function something like:

    T foo(T,S)(S x)

that takes arrays of various kinds and returns an element of the base 
type (well really something derived from the base type, but that part's 
easy).

The trick is that what I'd really like is for it be able to be used in 
all of the following ways:

   // IFTI
   foo(3)    // T=int S=int
   foo([3])  // T=int S=int[]
   foo([[3]])  // T=int S=int[][]
   foo([[[3]]])  // T=int S=int[][][]
   ... etc

   // Base type explicit
   foo!(float)(3)  // T=float S=float
   foo!(float)([3])  // T=float S=float[]
   foo!(float)([[3]])  // T=float S=float[][]
   ... etc

It's easy if you say you have to call it like foo!(float[][])([[3]]), 
but that's annoying.

Any bright ideas?

--bb
Jan 31 2007
parent reply Kirk McDonald <kirklin.mcdonald gmail.com> writes:
Bill Baxter wrote:
 I'd like to write a template function something like:
 
    T foo(T,S)(S x)
 
 that takes arrays of various kinds and returns an element of the base 
 type (well really something derived from the base type, but that part's 
 easy).
 
 The trick is that what I'd really like is for it be able to be used in 
 all of the following ways:
 
   // IFTI
   foo(3)    // T=int S=int
   foo([3])  // T=int S=int[]
   foo([[3]])  // T=int S=int[][]
   foo([[[3]]])  // T=int S=int[][][]
   ... etc
 
   // Base type explicit
   foo!(float)(3)  // T=float S=float
   foo!(float)([3])  // T=float S=float[]
   foo!(float)([[3]])  // T=float S=float[][]
   ... etc
 
 It's easy if you say you have to call it like foo!(float[][])([[3]]), 
 but that's annoying.
 
 Any bright ideas?
 
 --bb

This only works for dynamic arrays, but: typeof(T.init[0]) foo(T)(T x) {} -- Kirk McDonald Pyd: Wrapping Python with D http://pyd.dsource.org
Feb 01 2007
parent Bill Baxter <dnewsgroup billbaxter.com> writes:
Kirk McDonald wrote:
 Bill Baxter wrote:
 I'd like to write a template function something like:

    T foo(T,S)(S x)

 that takes arrays of various kinds and returns an element of the base 
 type (well really something derived from the base type, but that 
 part's easy).

 The trick is that what I'd really like is for it be able to be used in 
 all of the following ways:

   // IFTI
   foo(3)    // T=int S=int
   foo([3])  // T=int S=int[]
   foo([[3]])  // T=int S=int[][]
   foo([[[3]]])  // T=int S=int[][][]
   ... etc

   // Base type explicit
   foo!(float)(3)  // T=float S=float
   foo!(float)([3])  // T=float S=float[]
   foo!(float)([[3]])  // T=float S=float[][]
   ... etc

 It's easy if you say you have to call it like foo!(float[][])([[3]]), 
 but that's annoying.

 Any bright ideas?

 --bb

This only works for dynamic arrays, but: typeof(T.init[0]) foo(T)(T x) {}

Just getting the base type of the array is not what I'm after. The ultimate goal is to write something that's as close as possible to NumPy's 'asarray' function, a function which takes a wide range of input types and returns an n-dimensional "Array!(Type)" object built from that data. The trick is that in some cases I might like to coerce the data type. Like asarray!(cfloat)([[1,2],[3,4]]) but with the above asarray(T)(T x) declaration that gives an error like "int[][] is not a cfloat". I suspect I may just have to settle for two versions like asarray(T)(T x) and template asarray_of_type(AT) { asarray_of_type(T)(T x) {} } Yeh, that doesn't seem so bad actually. --bb
Feb 01 2007