Package net.hydromatic.morel.ast

Class FromBuilder

java.lang.Object

net.hydromatic.morel.ast.FromBuilder

public class FromBuilder
extends Object

Builds a Core.From.

Simplifies the following patterns:

• Converts "from v in list" to "list" (only works in buildSimplify(), not build());
• Removes "where true" steps;
• Removes empty "order" steps;
• Removes trivial yield, e.g. "from v in list where condition yield v" becomes "from v in list where condition";
• Inlines from expressions, e.g. "from v in (from w in list)" becomes "from w in list yield {v = w}".

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private class	FromBuilder.StepHandler	Calls the method to re-register a step.
private static class	FromBuilder.TupleType	Category of expression passed to "yield".

Field Summary

Fields

Modifier and Type	Field	Description
private List<Binding>	bindings
private @Nullable Environment	env
private int	removeIfLastIndex	If non-negative, flags that particular step should be removed if it is the last step.
private int	removeIfNotLastIndex	If non-negative, flags that particular step should be removed if it is not the last step.
private List<Core.FromStep>	steps
private TypeSystem	typeSystem

Constructor Summary

Constructors

Constructor	Description
FromBuilder(TypeSystem typeSystem, @Nullable Environment env)	Use CoreBuilder.fromBuilder(net.hydromatic.morel.type.TypeSystem, net.hydromatic.morel.compile.Environment).

Method Summary

Modifier and Type	Method	Description
FromBuilder	addAll(Iterable<? extends Core.FromStep> steps)
private FromBuilder	addStep(Core.FromStep step)
List<Binding>	bindings()	Returns the bindings available after the most recent step.
Core.From	build()
private Core.Exp	build(boolean simplify)
Core.Exp	buildSimplify()	As build(boolean), but also simplifies "from x in list" to "list".
FromBuilder	group(SortedMap<Core.IdPat,Core.Exp> groupExps, SortedMap<Core.IdPat,Core.Aggregate> aggregates)
private boolean	isRename(Core.Tuple tuple)	Returns whether tuple is something like "{i = j, j = x}".
private boolean	isTrivial(Core.Tuple tuple, @Nullable List<Binding> bindings2)	Returns whether tuple is something like "{i = i, j = j}".
FromBuilder	order(Iterable<Core.OrderItem> orderItems)
FromBuilder	scan(Core.Pat pat, Core.Exp exp)
FromBuilder	scan(Core.Pat pat, Core.Exp exp, Core.Exp condition)
private FromBuilder.TupleType	tupleType(Core.Tuple tuple, @Nullable List<Binding> bindings2)	Returns whether tuple is something like "{i = i, j = j}".
FromBuilder	where(Core.Exp condition)
FromBuilder	yield_(boolean uselessIfLast, @Nullable List<Binding> bindings2, Core.Exp exp)	Creates a "yield" step.
FromBuilder	yield_(boolean uselessIfLast, Core.Exp exp)
FromBuilder	yield_(Core.Exp exp)

Methods inherited from class java.lang.Object

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

Field Detail

typeSystem

private final TypeSystem typeSystem

env

private final @Nullable Environment env

steps

private final List<Core.FromStep> steps

bindings

private final List<Binding> bindings

removeIfNotLastIndex

private int removeIfNotLastIndex

If non-negative, flags that particular step should be removed if it is not the last step. (For example, "yield {i = i}", which changes the result shape if the last step but is otherwise a no-op.)

removeIfLastIndex

private int removeIfLastIndex

If non-negative, flags that particular step should be removed if it is the last step. (For example, we flatten "from p in (from q in list)", to "from q in list yield {p = q}" but we want to remove "yield {p = q}" if it turns out to be the last step.)

Constructor Detail

FromBuilder

FromBuilder(TypeSystem typeSystem,
            @Nullable Environment env)

Use CoreBuilder.fromBuilder(net.hydromatic.morel.type.TypeSystem, net.hydromatic.morel.compile.Environment).

Method Detail

bindings

public List<Binding> bindings()

Returns the bindings available after the most recent step.

addStep

private FromBuilder addStep(Core.FromStep step)

scan

public FromBuilder scan(Core.Pat pat,
                        Core.Exp exp)

scan

public FromBuilder scan(Core.Pat pat,
                        Core.Exp exp,
                        Core.Exp condition)

addAll

public FromBuilder addAll(Iterable<? extends Core.FromStep> steps)

where

public FromBuilder where(Core.Exp condition)

group

public FromBuilder group(SortedMap<Core.IdPat,Core.Exp> groupExps,
                         SortedMap<Core.IdPat,Core.Aggregate> aggregates)

order

public FromBuilder order(Iterable<Core.OrderItem> orderItems)

yield_

public FromBuilder yield_(Core.Exp exp)

yield_

public FromBuilder yield_(boolean uselessIfLast,
                          Core.Exp exp)

yield_

public FromBuilder yield_(boolean uselessIfLast,
                          @Nullable List<Binding> bindings2,
                          Core.Exp exp)

Creates a "yield" step.

When copying, the bindings2 parameter is the Core.FromStep.bindings value of the current Yield, so that we don't generate new variables (with different ordinals). Later steps are relying on the variables remaining the same. For example, in

from ... yield {a = b} where a > 5

the a in a > 5 references IdPat('a', 0) and we don't want yield to generate an IdPat('a', 1).

Parameters:

uselessIfLast - Whether this Yield will be useless if it is the last step. The expression {x = y} is an example of this

bindings2 - Desired bindings, or null

exp - Expression to yield

Returns:

This FromBuilder, with a Yield added to the list of steps

isTrivial

private boolean isTrivial(Core.Tuple tuple,
                          @Nullable List<Binding> bindings2)

Returns whether tuple is something like "{i = i, j = j}".

tupleType

private FromBuilder.TupleType tupleType(Core.Tuple tuple,
                                        @Nullable List<Binding> bindings2)

Returns whether tuple is something like "{i = i, j = j}".

isRename

private boolean isRename(Core.Tuple tuple)

Returns whether tuple is something like "{i = j, j = x}".

build

private Core.Exp build(boolean simplify)

build

public Core.From build()

buildSimplify

public Core.Exp buildSimplify()

As build(boolean), but also simplifies "from x in list" to "list".