Expression

java.lang.Object
- la.la.Expression

Direct Known Subclasses:

Expression.Application, Expression.Binary, Expression.Block, Expression.Const, Expression.Ident, Expression.IfExp, Expression.LambdaExp, Expression.Tuple, Expression.Unary
```
public abstract class Expression
extends java.lang.Object
```
Class Expression defines the abstract-syntax (i.e., parse tree) of Expressions in the language; also see Value.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`Expression.Application` A Function application `(e1 e2)`, where e1 must evaluate to a `Function`.
`static class`	`Expression.Binary` `(e1 op e2)`; yes it's just a special kind of `Expression.Application`.
`static class`	`Expression.Block` `let <Decs> in e`.
`static class`	`Expression.Const` Various Constants (literals) of the language; can be `eval-uated` at "compile" time; see `defer`.
`static class`	`Expression.Ident` An Identifier, 'id', as (it should have been) declared in `let id = e in e`, or `λid.e` .
`static class`	`Expression.IfExp` `(if e1 then e2 else e3)`; yes it's just a special kind of `Expression.Application` -- of `cond = \x1.\x2.\x3.x1 x2 x3`
`static class`	`Expression.LambdaExp` `λ x.e` denotes a `Function`.
`static class`	`Expression.Tuple` `(e0, e1, ...)`; also see `Value.Tuple`.
`static class`	`Expression.Unary` `(op e)`; yes it's just a special kind of `Expression.Application`.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`APPLICATION` A tag; see `n()`.
`static int`	`BINARY` A tag; see `n()`.
`static int`	`BLOCK` A tag; see `n()`.
`static int`	`CONST` A tag; see `n()`.
`static Expression.Const`	`ffalse` `Expression.Constant` false; see `Value.ffalse`.
`static int`	`IDENT` A tag; see `n()`.
`static int`	`IFEXP` A tag; see `n()`.
`static int`	`LAMBDAEXP` A tag; see `n()`.
`static Expression.Const`	`nilCon` `Expression.Constant` nil; see `Value.nilVal`.
`static Expression.Const`	`triv` `Expression.Constant` triv; see `Value.triv`.
`static Expression.Const`	`ttrue` `Expression.Constant` true; see `Value.ttrue`.
`static int`	`TUPLE` A tag; see `n()`.
`static int`	`UNARY` A tag; see `n()`.

Constructor Summary

Constructors
Constructor and Description

Expression()

Constructors
Constructor and Description
`Expression()`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract void`	`appendSB(java.lang.StringBuffer sb)` The use of a StringBuffer, sb, gives linear complexity when printing large Values; also see `toString()`.
`Value`	`defer(Environment r)` In general, create a `Defer(this,r)`, a "thunk", to evaluate 'this' Expression later, but also see `Expression.Const.defer(la.la.Environment)` and `Expression.LambdaExp.defer(la.la.Environment)`.
`void`	`error(java.lang.String msg)` Throw a RuntimeException.
`Value`	`eval(Environment r)` EVALuate 'this' `Expression`, using Environment 'r', to produce a `Value`.
`abstract int`	`n()` n(), the numerical code (tag) of a subclass of Expression, for example, for `switch`-ing.
`java.lang.String`	`toString()` The use of `appendSB(java.lang.StringBuffer)`, and hence a StringBuffer, gives linear rather than quadratic complexity.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - IDENT
```
public static final int IDENT
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - CONST
```
public static final int CONST
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - TUPLE
```
public static final int TUPLE
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - LAMBDAEXP
```
public static final int LAMBDAEXP
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - APPLICATION
```
public static final int APPLICATION
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - UNARY
```
public static final int UNARY
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - BINARY
```
public static final int BINARY
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - IFEXP
```
public static final int IFEXP
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - BLOCK
```
public static final int BLOCK
```
    A tag; see n().
    
    See Also:
    
    Constant Field Values
  - ttrue
```
public static final Expression.Const ttrue
```
    Expression.Constant true; see Value.ttrue.
  - ffalse
```
public static final Expression.Const ffalse
```
    Expression.Constant false; see Value.ffalse.
  - triv
```
public static final Expression.Const triv
```
    Expression.Constant triv; see Value.triv.
  - nilCon
```
public static final Expression.Const nilCon
```
    Expression.Constant nil; see Value.nilVal.
- Constructor Detail
  - Expression
```
public Expression()
```
- Method Detail
  - appendSB
```
public abstract void appendSB(java.lang.StringBuffer sb)
```
    The use of a StringBuffer, sb, gives linear complexity when printing large Values; also see toString().
  - toString
```
public java.lang.String toString()
```
    The use of appendSB(java.lang.StringBuffer), and hence a StringBuffer, gives linear rather than quadratic complexity.
    
    Overrides:
    
    toString in class java.lang.Object
  - n
```
public abstract int n()
```
    n(), the numerical code (tag) of a subclass of Expression, for example, for switch-ing.
  - defer
```
public Value defer(Environment r)
```
    In general, create a Defer(this,r), a "thunk", to evaluate 'this' Expression later, but also see Expression.Const.defer(la.la.Environment) and Expression.LambdaExp.defer(la.la.Environment).
  - eval
```
public Value eval(Environment r)
```
    EVALuate 'this' Expression, using Environment 'r', to produce a Value. Implements the tail-recursion optimisation. Acts directly for Expression.Application, Expression.Block and Expression.IfExp.
  - error
```
public void error(java.lang.String msg)
```
    Throw a RuntimeException.

Class Expression

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

IDENT

CONST

TUPLE

LAMBDAEXP

APPLICATION

UNARY

BINARY

IFEXP

BLOCK

ttrue

ffalse

triv

nilCon

Constructor Detail

Expression

Method Detail

appendSB

toString

n

defer

eval

error