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Cleaned up IfNodes

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- renamed rewrite_condition() to switches_over(),
   and @switcher to @switch_subject
 - removed unused else_body constructor parameter, as well
   as unnecessary push() method
 - ensure both @body and @else_body are always Expressions
   (previously they could be either Expressions or IfNode)
This commit is contained in:
gfxmonk
2010-04-27 23:32:45 +10:00
parent b47188763c
commit c8e0f8b149
5 changed files with 122 additions and 109 deletions
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78
src/nodes.coffee
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@@ -1156,21 +1156,21 @@ statement ForNode
# because ternaries are already proper expressions, and don't need conversion.
exports.IfNode: class IfNode extends BaseNode
constructor: (condition, body, else_body, tags) ->
constructor: (condition, body, tags) ->
@condition: condition
@body: body and body.unwrap()
@else_body: else_body and else_body.unwrap()
@children: compact flatten [@condition, @body, @else_body]
@body: body
@else_body: null
@populate_children()
@tags: tags or {}
@multiple: true if @condition instanceof Array
@condition: new OpNode('!', new ParentheticalNode(@condition)) if @tags.invert
@is_chain: false
# Add a new *else* clause to this **IfNode**, or push it down to the bottom
# of the chain recursively.
push: (else_body) ->
eb: else_body.unwrap()
if @else_body then @else_body.push(eb) else @else_body: eb
this
populate_children: ->
@children: compact flatten [@condition, @body, @else_body]
body_node: -> @body?.unwrap()
else_body_node: -> @else_body?.unwrap()
force_statement: ->
@tags.statement: true
@@ -1178,43 +1178,43 @@ exports.IfNode: class IfNode extends BaseNode
# Tag a chain of **IfNodes** with their object(s) to switch on for equality
# tests. `rewrite_switch` will perform the actual change at compile time.
rewrite_condition: (expression) ->
@switcher: expression
switches_over: (expression) ->
@switch_subject: expression
this
# Rewrite a chain of **IfNodes** with their switch condition for equality.
# Ensure that the switch expression isn't evaluated more than once.
rewrite_switch: (o) ->
assigner: @switcher
unless @switcher.unwrap() instanceof LiteralNode
assigner: @switch_subject
unless (@switch_subject.unwrap() instanceof LiteralNode)
variable: literal(o.scope.free_variable())
assigner: new AssignNode(variable, @switcher)
@switcher: variable
assigner: new AssignNode(variable, @switch_subject)
@children.push(assigner)
@switch_subject: variable
@condition: if @multiple
for cond, i in @condition
new OpNode('==', (if i is 0 then assigner else @switcher), cond)
new OpNode('==', (if i is 0 then assigner else @switch_subject), cond)
else
new OpNode('==', assigner, @condition)
@else_body.rewrite_condition(@switcher) if @is_chain()
@else_body_node().switches_over(@switch_subject) if @is_chain
# prevent this rewrite from happening again
@switch_subject: undefined
this
# Rewrite a chain of **IfNodes** to add a default case as the final *else*.
add_else: (exprs, statement) ->
if @is_chain()
@else_body.add_else exprs, statement
add_else: (else_body, statement) ->
if @is_chain
@else_body_node().add_else else_body, statement
else
exprs: exprs.unwrap() unless statement
@children.push @else_body: exprs
@is_chain: else_body instanceof IfNode
@else_body: @ensure_expressions else_body
@populate_children()
this
# If the `else_body` is an **IfNode** itself, then we've got an *if-else* chain.
is_chain: ->
@chain: or @else_body and @else_body instanceof IfNode
# The **IfNode** only compiles into a statement if either of its bodies needs
# to be a statement. Otherwise a ternary is safe.
is_statement: ->
@statement: or !!(@comment or @tags.statement or @body.is_statement() or (@else_body and @else_body.is_statement()))
@statement: or !!(@comment or @tags.statement or @body_node().is_statement() or (@else_body and @else_body_node().is_statement()))
compile_condition: (o) ->
(cond.compile(o) for cond in flatten([@condition])).join(' || ')
@@ -1223,14 +1223,18 @@ exports.IfNode: class IfNode extends BaseNode
if @is_statement() then @compile_statement(o) else @compile_ternary(o)
make_return: ->
@body: and @body.make_return()
@else_body: and @else_body.make_return()
@body: and @ensure_expressions(@body.make_return())
@else_body: and @ensure_expressions(@else_body.make_return())
this
ensure_expressions: (node) ->
node: new Expressions([node]) unless node instanceof Expressions
node
# Compile the **IfNode** as a regular *if-else* statement. Flattened chains
# force inner *else* bodies into statement form.
compile_statement: (o) ->
@rewrite_switch(o) if @switcher
@rewrite_switch(o) if @switch_subject
child: del o, 'chain_child'
cond_o: merge o
o.indent: @idt 1
@@ -1238,19 +1242,19 @@ exports.IfNode: class IfNode extends BaseNode
if_dent: if child then '' else @idt()
com_dent: if child then @idt() else ''
prefix: if @comment then "${ @comment.compile(cond_o) }\n$com_dent" else ''
body: Expressions.wrap([@body]).compile(o)
body: @body.compile(o)
if_part: "$prefix${if_dent}if (${ @compile_condition(cond_o) }) {\n$body\n$@tab}"
return if_part unless @else_body
else_part: if @is_chain()
' else ' + @else_body.compile(merge(o, {indent: @idt(), chain_child: true}))
else_part: if @is_chain
' else ' + @else_body_node().compile(merge(o, {indent: @idt(), chain_child: true}))
else
" else {\n${ Expressions.wrap([@else_body]).compile(o) }\n$@tab}"
" else {\n${ @else_body.compile(o) }\n$@tab}"
"$if_part$else_part"
# Compile the IfNode as a ternary operator.
compile_ternary: (o) ->
if_part: @condition.compile(o) + ' ? ' + @body.compile(o)
else_part: if @else_body then @else_body.compile(o) else 'null'
if_part: @condition.compile(o) + ' ? ' + @body_node().compile(o)
else_part: if @else_body then @else_body_node().compile(o) else 'null'
"$if_part : $else_part"
# Faux-Nodes