The writing rules for expression x in loop functions

Description:

Introduce the common rules on expressions in loop functions.

Note:

Expression x in loop functions such as r.(x), r.run(x), A.(x), A.run(x) and so on, should follow the rules below:

Ø  Members: ~ and A.~. ~ means the record being processed currently.

 

 

A

 

1

=demo.query("select * from EMPLOYEE")

 

2

=A1.(age(~.HIREDATE))

[9,6,3,7,9,8,…]

3

=A1.new(~.NAME:Name,age(~.HIREDATE):Workage)

 

Ø  Sequence numbers: # and A.#. # indicates the sequence number of the members.

 

 

A

[1,2,3,4,5,6,7,8…], the two results are the same

1

=demo.query("select * from EMPLOYEE")

2

=A1.(#)

3

=A1.(A1.#)

 

Ø  Fields: F, ~.F, r.F and A. F are equal to A.~. F , and A.F is equal to A(1).F if there is not a loop.

 

 

A

 

1

=demo.query("select * from EMPLOYEE")

 

2

=A1.(age(HIREDATE))

 [9,6,3,7,9,8,…], the results of the three expressions are the same.

 

3

=A1.(age(~.HIREDATE))

4

=A1.(age(A1.HIREDATE))

5

=A1.HIREDATE

2005-03-11, it is equal to A1(1).HIREDATE if

there is not a loop.

 

Ø  A[i] and ~[i] are equal to A(#+i) in the loop, which counts the members forward from the current member in A and return the ith member. If the boundary is exceeded, errors are not reported and null is returned. F[] is equal to A[].F

 

 

A

 

1

=demo.query("select ORDERID,AMOUNT,'' as ACCUMULATION from SALES")

 

2

=A1.run(ACCUMULATION=AMOUNT+ACCUMULATION[-1])

Obtain the current ACCUMULATION by adding the ACCUMULATION of the last record to the current AMOUNT.

 

Ø  A[a,b] and ~[a,b] in the loop indicate a sequence composed of members between A(#+a) and A(#+b). a is 1-# by default and b is A.len()-# by default.

 

 

A

 

1

=demo.query("select STOCKID,DATE,CLOSING,'' as FirstThree from STOCKRECORDS")

 

2

=A1.run(FIRSTTHREE=~[--3,-1].(CLOSING).avg())

~[-3,-1] indicates a sequence composed of three records counted backward from the current row.

 

Ø  Iteration: A1.f1(A2.f2(x))

Symbols in expression x will be first identified to serve A2; if expression x serves A1, the iteration will be . A1.f1(A2.f2(A1.x)).

 

A

 

1

=demo.query("select * from EMPLOYEE")

 

2

=demo.query("select * from DEPARTMENT")

 

3

=A2.run(MANAGER=A1.select@1(EID==A2.~.MANAGER).NAME)

Reference the nested loop

 

Ø  Aggregate: A.f(x) 

A.f(x) is equal to A.(x).f(), in which f is an aggregate function and x can be null.

Note:

The x in A.count(x) is a boolean expression, which is different from the rule for other aggregate functions.