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

Synopsis

Do a procedure with elements of lists

Stack Diagram

Input Stack						Output Stack
L₁	…	L_n	I_n	P_exec	→	L_results
L₁	…	L_n	I_n	N_exec	→	L_results
Level n+2	…	Level 3	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 DOLIST command EVALuates a specified program (or a variable which contains one) to lists of objects.

All lists must be the same length len. The program is executed len times: on the i-th iteration, I_n objects each taken from the i-th position in each list are entered on the stack in the same order as in their original lists, and the program P_exec is EVALuated. The results from each execution are left on the stack.

After the final iteration, any new results are combined into a single list: the UNMIX program presented here can help disentangling the results.

Compatibility

DOLIST is not fully equivalent to its userRPL counterpart.

In particular:

in userRPL the number of arguments can be omitted under certain conditions; in newRPL it must be always specified;
the program launched by DOLIST operates in a protected stack environment: no elements present on the stack before DOLIST is launched can be reached or altered.

Usage

Input

5:                             { 1 2 3 }
4:                             { 4 5 6 }
3:                             { 7 8 9 }
2:                                     3
1:                               « + * »
…………………………………………………………………………………………………………
DOLIST

Output

4:                                      
3:                                      
2:                                      
1:                          { 11 26 45 }
…………………………………………………………………………………………………………

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