--- a/PPExpressionParser.st Fri May 04 23:58:48 2012 +0200
+++ b/PPExpressionParser.st Fri May 04 23:59:01 2012 +0200
@@ -7,48 +7,6 @@
category:'PetitParser-Tools'
!
-PPExpressionParser comment:'A PPExpressionParser is a parser to conveniently define an expression grammar with prefix, postfix, and left- and right-associative infix operators.
-The following code initializes a parser for arithmetic expressions. First we instantiate an expression parser, a simple parser for expressions in parenthesis and a simple parser for integer numbers.
- expression := PPExpressionParser new.
- parens := $( asParser token trim , expression , $) asParser token trim
- ==> [ :nodes | nodes second ].
- integer := #digit asParser plus token trim
- ==> [ :token | token value asInteger ].
-
-Then we define on what term the expression grammar is built on:
- expression term: parens / integer.
-
-Finally we define the operator-groups in descending precedence. Note, that the action blocks receive both, the terms and the parsed operator in the order they appear in the parsed input.
-
- expression
- group: [ :g |
- g prefix: $- asParser token trim do: [ :op :a | a negated ] ];
- group: [ :g |
- g postfix: ''++'' asParser token trim do: [ :a :op | a + 1 ].
- g postfix: ''--'' asParser token trim do: [ :a :op | a - 1 ] ];
- group: [ :g |
- g right: $^ asParser token trim do: [ :a :op :b | a raisedTo: b ] ];
- group: [ :g |
- g left: $* asParser token trim do: [ :a :op :b | a * b ].
- g left: $/ asParser token trim do: [ :a :op :b | a / b ] ];
- group: [ :g |
- g left: $+ asParser token trim do: [ :a :op :b | a + b ].
- g left: $- asParser token trim do: [ :a :op :b | a - b ] ].
-
-After evaluating the above code the ''expression'' is an efficient parser that evaluates examples like:
- expression parse: ''-8++''.
- expression parse: ''1+2*3''.
- expression parse: ''1*2+3''.
- expression parse: ''(1+2)*3''.
- expression parse: ''8/4/2''.
- expression parse: ''8/(4/2)''.
- expression parse: ''2^2^3''.
- expression parse: ''(2^2)^3''.
-
-Instance Variables:
- operators <Dictionary> The operators defined in the current group.'
-!
-
!PPExpressionParser methodsFor:'private'!
@@ -76,10 +34,10 @@
ifTrue: [ term ]
ifFalse: [
self
- perform: selector with: term
+ perform: selector with: term
with: (list size = 1
ifTrue: [ list first first ==> [ :operator | Array with: list first second with: operator ] ]
- ifFalse: [
+ ifFalse: [
list
inject: PPChoiceParser new
into: [ :choice :each | choice / (each first ==> [ :operator | Array with: each second with: operator ]) ] ]) ] ]
@@ -102,17 +60,17 @@
group: aOneArgumentBlock
"Defines a priority group by evaluating aOneArgumentBlock."
-
+
operators := Dictionary new.
- parser := [
+ parser := [
aOneArgumentBlock value: self.
- self buildOn: parser ]
+ self buildOn: parser ]
ensure: [ operators := nil ]
!
left: aParser do: aThreeArgumentBlock
"Define an operator aParser that is left-associative. Evaluate aThreeArgumentBlock with the first term, the operator, and the second term."
-
+
self operator: #build:left: parser: aParser do: aThreeArgumentBlock
!
@@ -130,13 +88,13 @@
right: aParser do: aThreeArgumentBlock
"Define an operator aParser that is right-associative. Evaluate aThreeArgumentBlock with the first term, the operator, and the second term."
-
+
self operator: #build:right: parser: aParser do: aThreeArgumentBlock
!
term: aParser
"Defines the initial term aParser of the receiver."
-
+
parser isNil
ifTrue: [ parser := aParser ]
ifFalse: [ self error: 'Unable to redefine the term.' ]
@@ -144,6 +102,14 @@
!PPExpressionParser class methodsFor:'documentation'!
+version
+ ^ '$Header: /cvs/stx/stx/goodies/petitparser/PPExpressionParser.st,v 1.3 2012-05-04 21:59:01 vrany Exp $'
+!
+
+version_CVS
+ ^ '$Header: /cvs/stx/stx/goodies/petitparser/PPExpressionParser.st,v 1.3 2012-05-04 21:59:01 vrany Exp $'
+!
+
version_SVN
- ^ '$Id: PPExpressionParser.st,v 1.2 2012-01-13 11:22:50 cg Exp $'
+ ^ '§Id: PPExpressionParser.st 2 2010-12-17 18:44:23Z vranyj1 §'
! !