Package net.hydromatic.morel.eval

Class Closure

java.lang.Object

net.hydromatic.morel.eval.Closure

All Implemented Interfaces:

Comparable<Closure>, Applicable, Describable

public class Closure
extends Object
implements Comparable<Closure>, Applicable

Value that is sufficient for a function to bind its argument and evaluate its body.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	Closure.EvalEnvHolder	Callback for bindRecurse(Core.Pat, Object, BiConsumer) that modifies an environment.

Field Summary

Fields

Modifier and Type	Field	Description
private EvalEnv	evalEnv	Environment for evaluation.
private com.google.common.collect.ImmutableList<Pair<Core.Pat,Code>>	patCodes	A list of (pattern, code) pairs.
private Pos	pos

Constructor Summary

Constructors

Constructor	Description
Closure(EvalEnv evalEnv, com.google.common.collect.ImmutableList<Pair<Core.Pat,Code>> patCodes, Pos pos)	Not a public API.

Method Summary

Modifier and Type	Method	Description
Object	apply(EvalEnv env, Object argValue)
(package private) EvalEnv	bind(Object argValue)	Binds an argument value to create a new environment for a closure.
(package private) Object	bindEval(Object argValue)	Similar to bind(java.lang.Object), but also evaluates.
static boolean	bindRecurse(Core.Pat pat, Object argValue, BiConsumer<Core.NamedPat,Object> envRef)	Attempts to bind a value to a pattern.
int	compareTo(Closure o)
Describer	describe(Describer describer)
(package private) EvalEnv	evalBind(EvalEnv env)	Similar to bind(java.lang.Object), but evaluates an expression first.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.hydromatic.morel.eval.Applicable

asCode

Field Detail

evalEnv

private final EvalEnv evalEnv

Environment for evaluation. Contains the variables "captured" from the environment when the closure was created.

patCodes

private final com.google.common.collect.ImmutableList<Pair<Core.Pat,Code>> patCodes

A list of (pattern, code) pairs. During bind, the value being bound is matched against each pattern. When a match is found, the code for that pattern is used to evaluate.

For example, when applying fn x => case x of 0 => "yes" | _ => "no" to the value 1, the first pattern (0 fails) but the second pattern (_) succeeds, and therefore we evaluate the second code "no".

pos

private final Pos pos

Constructor Detail

Closure

public Closure(EvalEnv evalEnv,
               com.google.common.collect.ImmutableList<Pair<Core.Pat,Code>> patCodes,
               Pos pos)

Not a public API.

Method Detail

toString

public String toString()

Overrides:

toString in class Object

compareTo

public int compareTo(Closure o)

Specified by:

compareTo in interface Comparable<Closure>

bind

EvalEnv bind(Object argValue)

Binds an argument value to create a new environment for a closure.

When calling a simple function such as (fn x => x + 1) 2, the binder sets just contains one variable, x, and the new environment contains x = 1. If the function's parameter is a match, more variables might be bound. For example, when you invoke (fn (x, y) => x + y) (3, 4), the binder sets x to 3 and y to 4.

evalBind

EvalEnv evalBind(EvalEnv env)

Similar to bind(java.lang.Object), but evaluates an expression first.

bindEval

Object bindEval(Object argValue)

Similar to bind(java.lang.Object), but also evaluates.

apply

public Object apply(EvalEnv env,
                    Object argValue)

Specified by:

apply in interface Applicable

describe

public Describer describe(Describer describer)

Specified by:

describe in interface Describable

bindRecurse

public static boolean bindRecurse(Core.Pat pat,
                                  Object argValue,
                                  BiConsumer<Core.NamedPat,Object> envRef)

Attempts to bind a value to a pattern. Returns whether it has succeeded in matching the whole pattern.

Each time it matches a name, calls a consumer. It's possible that the consumer is called a few times even if the whole pattern ultimately fails to match.