DOM_IDENT

Symbolic Identifiers

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Description

DOM_IDENT is the data type of symbolic identifiers, used for example for indeterminates.

To perform symbolic computations, it is often necessary to represent indeterminates, which may or may not carry assumptions. These indeterminates (which in some contexts may also be bound identifers and which may also be assigned specific values) are called “identifiers” in MuPAD^® and have the domain type DOM_IDENT.

Function Calls

Calling a DOM_IDENT as a function creates a DOM_EXPR. If the identifier has a value, the evaluation of that DOM_EXPR may result in an arbitrary value.

Operations

Identifiers are valid arithmetical expressions, so most MuPAD functions happily accept identifiers.

To get and analyze the name of an identifier, you can use coerce(identifier, DOM_STRING ) and look at the resulting string. (The call "".identifier returns the same string and is shorter to type.)

Operands

Identifiers are atomic.

Output

Identifiers are displayed with their names, with the following special cases in typesetting:

• Underscores (_) in the middle of identifiers cause subscripting: x_2 is displayed as x₂.

• Certain constructs of the form `&...;` in identifiers are replaced by special typeset characters. For example, `α→` is displayed as . To generate these identifiers, we suggest using the Symbol library, which would use Symbol::accentRightArrow(Symbol::alpha) for the example above.

Element Creation

A sequence of characters, underscores and digits which does not start with a digit is considered an identifier. Examples: x, x0, t_0.

Additionally, an arbitrary string of characters enclosed in ‘backticks’ `` is also an identifier. Examples: `x+y`, `a plus 1`. If the string of characters between the back ticks is a valid identifier already, this input form creates the same identifier as the one without the backticks.