Chapter 15: Expressions and The Expression Stack
169
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
An empty tail is represented by simply an END_TAG. Thus, rand( ) is
represented by END_TAG RAND_TAG.
15.2.8. Lists and Matrices
Most of the functions and operators in the system will operate on lists of
expressions and matrices containing expressions. A list is represented as a
LIST_TAG on top of a tail of expressions. Thus, the empty list { } is represented
as END_TAG LIST_TAG. The list {a,
π
, tan(x)} is represented by END_TAG
X_VAR_TAG TAN_TAG PI_TAG A_VAR_TAG LIST_TAG. None of the elements
of a list can be a list unless they all are equal length lists thus forming a matrix.
A matrix is represented as a list of lists. Each of the inner lists represents a row
of the matrix. For example, the matrix [a, b; c, d] is represented by END_TAG
END_TAG D_VAR_TAG C_VAR_TAG LIST_TAG END_TAG B_VAR_TAG
A_VAR_TAG LIST_TAG LIST_TAG. The lengths of the rows must be equal.
None of the elements of a row can be a list. The system neither generates nor
expects invalid list or matrix structures. They will cause unexpected system
behavior.
15.2.9. Primary, Secondary, and Command Tags
The tags discussed in the preceding sections are called primary tags. In each
case the single tag on top of the representation is all that is required to identify
that element. However, the Operating System provides more than 256 built-in
functions, operators, commands, programming constructs, and so on. Therefore,
some of the primary tags are used with additional one Quantum tag values to
provide additional identifiers.
The tag value SECONDARY_TAG is used with secondary tag values to provide
representation for additional functions and operators. For example, ORD_TAG
happens to have the same Quantum value as V_VAR_TAG, but a
SECONDARY_TAG on top of that Quantum value represents the ord() function
rather than the variable v.
Expression Representation
getKey( ) END_TAG GETKEY_TAG SECONDARY_TAG
#s S_VAR_TAG INDIRECTION_TAG SECONDARY_TAG
v
POL V_VAR_TAG TO_POLAR_TAG SECONDARY_TAG
Table 15.10: Secondary Tag Examples
Similarly, the primary tag value COMMAND_TAG is used on top of command tag
values to provide representation for elements of the TI
-
BASIC programming
language.
To Next Page
Loading...
Need help?
General
