Raze
⊃

Raze (⊃
), or ;
in J, is a monadic function which combines element arrays of a nested vector along the first axis (in accordance with leading axis theory). Thus, the major cells of the Raze of an array are the major cells of its element arrays: unlike Mix, which removes a level of depth while keeping outer and inner axes separate, Raze merges the outer vector's axis with the first axis of each element. Raze is present in A+ and J.
Examples
Raze can turn a vector of vectors into a single vector. Unlike Mix, it inserts no fill elements.
⊃(2 3 4;0 1;5)
2 3 4 0 1 5
When elements of the argument have rank more than 1, Raze combines them along the leading axis, like Catenate First. In A+, the elements must have the same rank and major cell shape or an error results; in J, lowerrank arrays are promoted to a higher rank and arrays are padded with fills to a common major cell shape.
⊃(⍳2 2;⍳4 2)
0 1
2 3
0 ¯1
¯2 ¯3
¯4 ¯5
¯6 ¯7
Properties
Raze is similar to the Catenate reduction ↑⍪/
. If X
is a vector whose elements have equal and positive rank, then ↑⍪/X
is the Raze of X
. The definition differs if X
is a singleton vector with scalar elements, because the Raze of X
will be a vector while the reduction implementation results in a scalar (or, in NARS2000, a DOMAIN ERROR). This is because Raze treats scalar elements of its argument as singleton vectors, a convention which may be viewed as scalar rank extension or as a result of the idea that a scalar's only major cell is itself.
Raze is the inverse of Partition and Partitioned Enclose on vectors: partitioning, then razing, a vector gives that vector back. It is also an inverse to partition functions which partition major cells along the first axis, although few partition functions do this.
External links
Documentation
 J Dictionary, NuVoc