manual:chapter6:operators:cmd_ovr_eval1 [newRPL User Manual]

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Synopsis

Evaluate an object, single pass

Stack Diagram

Input Stack		Output Stack
O	→	see list under Description
Level 1	→	Level n	…	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

Type	Operator
Parallel list processing	Yes, but specific group is determined by the object being evaluated
Affected by flags	-70	Global autosimplification rules
	-71	Application of Group 1 autosimplification rules
	-72	Application of Group 2 autosimplification rules
	-73	Application of Group 3 autosimplification rules
	-74	Application of Group 4 autosimplification rules
	-75	Application of Group 5 autosimplification rules
	-76	Application of Group 6 autosimplification rules
	-77	Application of Group 7 autosimplification rules
	-78	Application of Group 8 autosimplification rules
	-103	Complex results

Description

The EVAL1 command evaluates the object on the top level of the stack.

The effect of the evaluation and the resulting output depends on the type of object being evaluated, as summarized by the following list.

Local Name: EVAL1 recalls the content of the variable.
Global Name: EVAL1 calls the content of a variable:
1. a Name is evaluated;
2. a Program is evaluated;
3. a Directory becomes the current directory;
4. other objects which are not lists are put on the stack.
Program: EVAL1 enters each object in the program:
1. an unquoted Name is evaluated;
2. a Keyword is XEQted;
3. other objects which are not lists are put on the stack.
Symbolic expression: EVAL1 enters each object in the expression:
1. a Name is evaluated;
2. a Keyword is XEQted;
3. other objects which are not lists are put on the stack.
Other objects: if they are not lists EVAL1 puts them on the stack.
List: EVAL1 enters each object in the list:
1. any object is evaluated according above mentioned rules.

As a final step, EVAL1 will perform numerical simplification according to the status of flags from -70 to -78. If the final results

The main difference from EVAL is that EVAL1 performs only one step of the process described above, allowing evaluation of recursive formulas that would otherwise yield a Circular reference error.

Compatibility

This command is new in newRPL and does not exist in userRPL.

Usage

If the following command is executed

2:                         'X+1'
1:                           'X'
……………………………………………………………………………………
STO

then the command

1:                           'X'
……………………………………………………………………………………
EVAL

would return a Circular reference error.

Instead

1:                           'X'
……………………………………………………………………………………
EVAL1

will result in

1:                         'X+1'
……………………………………………………………………………………

and further use of EVAL1 will return 'X+2', 'X+3', et cetera.

Related Commands

Overloadable operators 26 3 NEW

Operator	Short Description
Evaluation operators:
EVAL1	Evaluate one level	NEW
EVAL	Evaluate full depth
XEQ	Execute	NEW
→NUM	Compute numeric result
Test operators:
==	Equality test
≠	Not equal test
<	Less than test
≤	Less than or equal test
>	Greater than test
≥	Greater than or equal test
CMP	Comparison test (<0 if A<B, 0 if A==B, >0 if A>B)	NEW
SAME	Comparison test, true if objects are the same
ISTRUE	True test	NEW
Logical operators:
AND	Logical AND
OR	Logical OR
XOR	Logical XOR
NOT	Logical NOT
Mathematic operators:
+	Addition
-	Subtraction
*	Multiplication
/	Division
^	Power
XROOT	Root
INV	Inverse
NEG	Negate/change sign
ABS	Magnitude or absolute value