manual:chapter6:lists:cmd_stream [newRPL User Manual]

Synopsis

Assemble a list from results of sequential procedure

Stack Diagram

Input Stack			Output Stack
L_data	P_exec	→	O_result
L_data	N_exec	→	O_result
Level 2	Level 1	→	Level 1

Legend

Legend	Object type
O	Any object
I	Integer number
R	Real number
#	Binary number
Num	Scalar (Integer, Real or Binary number)
Z	Complex number
U	Unit
∡	Angle
A	Symbolic expression
C	Symbolic constant
V	Vector
M	Matrix
S	String
1/0	Any expression evaluating to True or False
G	Grob
F	Font
D	Binary data container
T	Tag object
L	List
cL	Case list
N	Variable name / Identifier
Dir	Directory
pDir	Packed Directory
P	Program
Lib	Library

Keyword type	Command
Parallel list processing capabilities	Group 2	Commands that must use `DOLIST` to parallel process
Affected by flags	None

Description

The STREAM command moves the first two elements from L_data onto the stack, EVALuating a program or an identifier. Then moves the next element (if any) onto the stack, and EVALuates P_exec (or N_exec) again using the previous result and the new element. Repeats this until L_data is exhausted, and returns the final result.

STREAM is nominally designed for P_exec (or N_exec) requiring two arguments and returning one result.

Compatibility

STREAM is not fully equivalent to its userRPL counterpart.

In particular:

the program launched by STREAM operates in a protected stack environment: no elements present on the stack before STREAM is launched can be reached or altered.

Usage

Input

4:                                      
3:                                      
2:                   { "A" "B" "C" "D" }
1:                            « SWAP + »
…………………………………………………………………………………………………………
STREAM

Output

4:                                      
3:                                      
2:                                      
1:                                "DCBA"
…………………………………………………………………………………………………………

Related Commands

Operations with Lists 15 2 NEW

Command	Short Description
→LIST	Assemble a list from its elements
LIST→	Split a list into its elements
DOLIST	Do a procedure with elements of lists	CHANGED
DOSUBS	Do a procedure on a subset of a list	CHANGED
MAP	Do a procedure on each element of a list, recursively
MAPLIST→	Do a procedure on each element recursively, return individual elements	NEW
STREAM	Do a procedure on consecutive elements of a list
ΔLIST	First differences on the elements of a list
ΣLIST	Sum of all elements in a list	CHANGED
ΠLIST	Product of all elements in a list	CHANGED
ADD	Concatenate lists and/or elements	CHANGED
SORT	Sort elements in a list
REVLIST	Reverse the order of elements in a list
ADDROT	Add elements to a list, keep only the last N elements	NEW
SEQ	Assemble a list from results of sequential procedure