Reference Guide

Full Command and Function Reference 3-271
VISIT
Type: Command
Description: For a specified variable, opens the contents in the command-line editor.
Access: …µ VISIT or „˜
Input/Output:
Level 1/Argument 1 Level 1/Item 1
A variable name
→
The contents opened in the command line
editor.
See also: VISITB, EDIT, EDITB
VISITB
Type: Command
Description: For a specified variable, opens the contents in the most suitable editor for the object type. For
example, if the specified variable holds an equation, the equation is opened in Equation Writer.
Access: …µ VISITB
Input/Output:
Level 1/Argument 1 Level 1/Item 1
A variable name
→
The contents opened in the most suitable
editor.
See also: VISIT, EDIT, EDITB
VPOTENTIAL
Type: Command
Description: Find a vector potential function describing a field whose curl (or “rot”) is the input. This
command is the opposite of CURL. Given a vector V it attempts to return a function U such that
curl U is equal to V; VU =×∇ . For this to be possible, DIV(V) must be zero, otherwise the
command reports a “Bad Argument Value” error. Step-by-step mode is available with this
command.
Access: Catalog, …µ
Input: Level 2/Argument 1: A vector V of expressions.
Level 1/Argument 2: A vector of the names of the variables.
Output: Level 1/Item 1: A vector U of the variables that is the potential from which V is obtained. An
arbitrary constant can be added, the command does not do this.
Flags: Exact mode must be set (flag –105 clear).
Numeric mode must not be set (flag –3 clear).
Radians mode must be set (flag –17 set).
Step-by-step mode can be set (flag –100 set).
Example: To see if this command is the opposite of CURL, use the output of the example in CURL as
input to VPOTENTIAL. Find a vector in the spatial variables x, y, and z whose curl is:
(2yz) i + (0) j + (2xy – x
2
) k
Command: VPOTENTIAL([2*Y*Z, 0, 2*X*Y-X^2], [X,Y,Z])
EXPAND(ANS(1))
Result: [0, -((X^3-3*Y*X^2)/3), Z*Y^2]
This shows that the reversal is not unique – more than one vector can have the same curl.