PPExpressionParser.st
changeset 11 e6e33e8fe655
parent 4 90de244a7fa2
child 427 a7f5e6de19d2
child 646 6e97d8145481
--- 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 §'
 ! !