net.cscott.sdr.calls.ast
Class If

java.lang.Object
  net.cscott.sdr.calls.ast.AstNode
      net.cscott.sdr.calls.ast.Comp
          net.cscott.sdr.calls.ast.If

public class If
extends Comp

If rejects its child as suitable for execution from the current formation unless its condition evaluates true.

Author:

C. Scott Ananian

Tests:

An If with no message

js> iff = new If(If.When.BEFORE, new Expr("true"), new Seq(Apply.makeApply("nothing")));
(If 'BEFORE (Expr true) (Seq (Apply 'nothing)))

An If with a message and the default priority:

js> iff = new If(If.When.AFTER, new Expr("true"), new Seq(Apply.makeApply("nothing")), "Message!");
(If 'AFTER (Expr true) (Seq (Apply 'nothing)) "Message!")

An If with a user-specified priority:

js> importPackage(net.cscott.sdr.util)
js> iff = new If(If.When.BEFORE, new Expr("true"), new Seq(Apply.makeApply("nothing")), "Message!", Fraction.ONE_HALF);
(If 'BEFORE (Expr true) (Seq (Apply 'nothing)) "Message!" 1/2)

Nested Class Summary

static class

If.When When to evaluate an If: before or after its child.

Field Summary

Comp	child The child to evaluate, iff the condition is true.
Expr	condition The condition to evaluate.
String	message User-friendly message to report if the condition fails, or null.
Fraction	priority Priority of the message: if a parallel operation causes failures in multiple places, the one with the highest priority will be reported.
If.When	when Evaluate condition before or after the child is evaluated?

Fields inherited from class net.cscott.sdr.calls.ast.AstNode

type

Constructor Summary

If(If.When when, Expr condition, Comp child)

If(If.When when, Expr condition, Comp child, String msg)

If(If.When when, Expr condition, Comp child, String msg, Fraction priority)

Method Summary

<T> Comp	accept(TransformVisitor<T> v, T t) Visitor pattern implementation for transformations.
<RESULT,CLOSURE> RESULT	accept(ValueVisitor<RESULT,CLOSURE> v, CLOSURE cl) Visitor pattern implementation for computations.
String	argsToString()
If	build(Expr condition, Comp child) Factory: creates new If only if it would differ from this.

Methods inherited from class net.cscott.sdr.calls.ast.AstNode

toString, valueOf

Methods inherited from class java.lang.Object

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

Field Detail

when

public final If.When when

Evaluate condition before or after the child is evaluated?

condition

public final Expr condition

The condition to evaluate. Should yield a boolean.

child

public final Comp child

The child to evaluate, iff the condition is true.

message

public final String message

User-friendly message to report if the condition fails, or null.

priority

public final Fraction priority

Priority of the message: if a parallel operation causes failures in multiple places, the one with the highest priority will be reported. The default priority is 1 if a message is specified, or else 0. Negative priorities can be used to specify nonfatal warnings.

Constructor Detail

If

public If(If.When when,
          Expr condition,
          Comp child)

If

public If(If.When when,
          Expr condition,
          Comp child,
          String msg)

If

public If(If.When when,
          Expr condition,
          Comp child,
          String msg,
          Fraction priority)

Method Detail

accept

public <T> Comp accept(TransformVisitor<T> v,
                       T t)

Description copied from class: AstNode

Visitor pattern implementation for transformations. Each AstNode accepts a TransformVisitor and a value, and returns an instance of its own type (ie, Seq.accept(tv, "A") returns a Seq). The 't' parameter is a closure.

Specified by:

accept in class Comp

accept

public <RESULT,CLOSURE> RESULT accept(ValueVisitor<RESULT,CLOSURE> v,
                                      CLOSURE cl)

Description copied from class: AstNode

Visitor pattern implementation for computations. Each AstNode accepts a ValueVisitor and a closure, and returns an object of the appropriate result type.

Specified by:

accept in class AstNode

build

public If build(Expr condition,
                Comp child)

Factory: creates new If only if it would differ from this.

argsToString

public String argsToString()

Overrides:

argsToString in class AstNode