evaluator: add environment, make definitions work, add tests

src/Phsyche.package/Phsyche.class/instance/eval..st

@@ -1,3 +1,3 @@
 as yet unclassified
-eval: expression
-	^ self eval: expression in: nil
+eval: expr
+	^ self eval: expr in: env

src/Phsyche.package/Phsyche.class/instance/eval.in..st

@@ -1,3 +1,9 @@
 as yet unclassified
-eval: expression in: anEnvironment
-	^ expression
+eval: expr in: environ
+	expr = #() ifTrue: [ ^ expr ].
+	expr isSymbol ifTrue: [ ^ environ at: expr ]. "returns the variable value"
+	expr isArray ifFalse: [ ^ expr ] "returns literals boolean, string, number"
+					 ifTrue: [
+						expr first = #define
+						ifTrue: [ ^ self evalDefine: expr in: environ ]
+					]

src/Phsyche.package/Phsyche.class/instance/evalDefine.in..st

@@ -0,0 +1,5 @@
+as yet unclassified
+evalDefine: expr in: environ
+	environ at: expr second
+			  put: (self eval: expr third in: environ).
+	^ #undefined

src/Phsyche.package/Phsyche.class/instance/initialize.st

@@ -0,0 +1,4 @@
+initialization
+initialize
+	super initialize.
+	env := Dictionary new

src/Phsyche.package/Phsyche.class/instance/parse..st

@@ -1,4 +1,4 @@
 as yet unclassified
-parse: aProgramString
-	aProgramString ifEmpty: [ ^ #() ].
-	^ (Scanner new scanTokens: aProgramString) first
+parse: prog
+	prog ifEmpty: [ ^ #() ].
+	^ (Scanner new scanTokens: prog) first

src/Phsyche.package/Phsyche.class/instance/parseAndEval..st

@@ -1,3 +1,3 @@
 as yet unclassified
-parseAndEval: anExpression
-	^ self eval: (self parse: anExpression)
+parseAndEval: expr
+	^ self eval: (self parse: expr)

src/Phsyche.package/PhsycheTest.class/instance/testDefineExpression.st

@@ -0,0 +1,6 @@
+tests
+testDefineExpression
+	ph parseAndEval: '(define pi 3.14)'.
+	self
+		assert: (ph parseAndEval: 'pi')
+		equals: 3.14

src/Phsyche.package/PhsycheTest.class/instance/testEvalExpressionReassignment.st

@@ -0,0 +1,6 @@
+tests
+testEvalExpressionReassignment
+	ph parseAndEval: '(define pi 3.14)'.
+	ph parseAndEval: '(define pi2 pi)'.
+	ph parseAndEval: '(define pi 6.28)'.
+	self assert: (ph parseAndEval: 'pi2') equals: 3.14