Revert "RFC: Move Colon translation out of the parser"

NEWS.md

@@ -114,11 +114,6 @@ Language changes
     macro. Instead, the string is first unindented and then `x_str` is invoked,
     as if the string had been single-quoted ([#10228]).
 
-  * Colons (`:`) within indexing expressions are no longer lowered to the range
-    `1:end`. Instead, the `:` identifier is passed directly. Custom array types
-    that implement `getindex` or `setindex!` methods must also extend those
-    methods to support arguments of type `Colon` ([#10331]).
-
 Command line option changes
 ---------------------------
 
@@ -1429,7 +1424,6 @@ Too numerous to mention.
 [#10180]: https://github.com/JuliaLang/julia/issues/10180
 [#10228]: https://github.com/JuliaLang/julia/issues/10228
 [#10328]: https://github.com/JuliaLang/julia/issues/10328
-[#10331]: https://github.com/JuliaLang/julia/issues/10331
 [#10332]: https://github.com/JuliaLang/julia/issues/10332
 [#10333]: https://github.com/JuliaLang/julia/issues/10333
 [#10380]: https://github.com/JuliaLang/julia/issues/10380

base/array.jl

@@ -343,20 +343,6 @@ function setindex!(A::Array, X::AbstractArray, I::AbstractVector{Int})
     end
     return A
 end
-function setindex!(A::Array, x, ::Colon)
-    for i in 1:length(A)
-        @inbounds A[i] = x
-    end
-    return A
-end
-function setindex!(A::Array, X::AbstractArray, ::Colon)
-    setindex_shape_check(X, length(A))
-    i = 0
-    for x in X
-        @inbounds A[i+=1] = x
-    end
-    return A
-end
 
 # Faster contiguous setindex! with copy!
 setindex!{T}(A::Array{T}, X::Array{T}, I::UnitRange{Int}) = (checkbounds(A, I); unsafe_setindex!(A, X, I))
@@ -378,6 +364,7 @@ function unsafe_setindex!{T}(A::Array{T}, X::Array{T}, ::Colon)
     return A
 end
 
+
 # efficiently grow an array
 
 function _growat!(a::Vector, i::Integer, delta::Integer)

doc/manual/arrays.rst

@@ -222,10 +222,9 @@ The general syntax for indexing into an n-dimensional array A is::
 where each ``I_k`` may be:
 
 1. A scalar integer
-2. A ``Range`` of the form ``a:b``, or ``a:b:c``
-3. A ``:`` or ``Colon()`` to select entire dimensions
-4. An arbitrary integer vector, including the empty vector ``[]``
-5. A boolean vector
+2. A ``Range`` of the form ``:``, ``a:b``, or ``a:b:c``
+3. An arbitrary integer vector, including the empty vector ``[]``
+4. A boolean vector
 
 The result ``X`` generally has dimensions
 ``(length(I_1), length(I_2), ..., length(I_n))``, with location
@@ -287,11 +286,10 @@ The general syntax for assigning values in an n-dimensional array A is::
 
 where each ``I_k`` may be:
 
-1. A scalar integer
-2. A ``Range`` of the form ``a:b``, or ``a:b:c``
-3. A ``:`` or ``Colon()`` to select entire dimensions
-4. An arbitrary integer vector, including the empty vector ``[]``
-5. A boolean vector
+1. A scalar value
+2. A ``Range`` of the form ``:``, ``a:b``, or ``a:b:c``
+3. An arbitrary integer vector, including the empty vector ``[]``
+4. A boolean vector
 
 If ``X`` is an array, its size must be ``(length(I_1), length(I_2), ..., length(I_n))``,
 and the value in location ``i_1, i_2, ..., i_n`` of ``A`` is overwritten with

src/julia-syntax.scm

@@ -301,17 +301,18 @@
 (define (expand-compare-chain e)
   (car (expand-vector-compare e)))
 
-;; return the appropriate computation for an `end` symbol for indexing
-;; the array `a` in the `n`th index.
-;; `tuples` are a list of the splatted arguments that precede index `n`
-;; `last` = is this last index?
-;; returns a call to endof(a), trailingsize(a,n), or size(a,n)
+;; last = is this last index?
 (define (end-val a n tuples last)
   (if (null? tuples)
       (if last
           (if (= n 1)
               `(call (top endof) ,a)
               `(call (top trailingsize) ,a ,n))
+              #;`(call (top div)
+                     (call (top length) ,a)
+                     (call (top *)
+                           ,@(map (lambda (d) `(call (top size) ,a ,(1+ d)))
+                                  (iota (- n 1)))))
           `(call (top size) ,a ,n))
       (let ((dimno `(call (top +) ,(- n (length tuples))
                           ,.(map (lambda (t) `(call (top length) ,t))
@@ -320,7 +321,8 @@
             `(call (top trailingsize) ,a ,dimno)
             `(call (top size) ,a ,dimno)))))
 
-; replace `end` for the closest ref expression, so doesn't go inside nested refs
+; replace end inside ex with (call (top size) a n)
+; affects only the closest ref expression, so doesn't go inside nested refs
 (define (replace-end ex a n tuples last)
   (cond ((eq? ex 'end)                (end-val a n tuples last))
         ((or (atom? ex) (quoted? ex)) ex)
@@ -333,7 +335,29 @@
                (map (lambda (x) (replace-end x a n tuples last))
                     (cdr ex))))))
 
-;; go through indices and replace the `end` symbol
+; translate index x from colons to ranges
+(define (expand-index-colon x)
+  (cond ((eq? x ':) `(call colon 1 end))
+        ((and (pair? x)
+              (eq? (car x) ':))
+         (cond ((length= x 3)
+                (if (eq? (caddr x) ':)
+                    ;; (: a :) a:
+                    `(call colon ,(cadr x) end)
+                    ;; (: a b)
+                    `(call colon ,(cadr x) ,(caddr x))))
+               ((length= x 4)
+                (if (eq? (cadddr x) ':)
+                    ;; (: a b :) a:b:
+                    `(call colon ,(cadr x) ,(caddr x) end)
+                    ;; (: a b c)
+                    `(call colon ,@(cdr x))))
+               (else x)))
+        (else x)))
+
+;; : inside indexing means 1:end
+;; expand end to size(a,n),
+;;     or div(length(a), prod(size(a)[1:(n-1)])) for the last index
 ;; a = array being indexed, i = list of indexes
 ;; returns (values index-list stmts) where stmts are statements that need
 ;; to execute first.
@@ -362,7 +386,8 @@
                           (cons `(... ,g) ret))))
               (loop (cdr lst) (+ n 1)
                     stmts tuples
-                    (cons (replace-end idx a n tuples last) ret)))))))
+                    (cons (replace-end (expand-index-colon idx) a n tuples last)
+                          ret)))))))
 
 (define (make-decl n t) `(|::| ,n ,t))