TXL parser for FL

git-svn-id: https://slps.svn.sourceforge.net/svnroot/slps@657 ab42f6e0-554d-0410-b580-99e487e6eeb2

topics/fl/txl/FL.Txl

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+% Calculator.Txl - simple numerical expression evaluator
+
+% Part I.  Syntax specification
+define program
+        [fun+]
+end define
+
+define fun
+        [id] [id+] = [expression] [newline]
+end define
+
+define expression
+        [expression] [op] [expression]
+    |   [id] [expression+]
+    |   if [expression] then [expression] else [expression]
+    |   [expression] == [expression]
+    |   [primary]
+end define
+
+define op
+        +
+    |   -
+    |   ==
+end define
+
+define primary 
+        [number]
+    |   [id]
+    |   ( [expression] )
+end define
+
+
+% Part 2.  Transformation rules
+rule main
+    replace [expression]
+        E [expression]
+    construct NewE [expression]
+        E [resolveAddition]
+          [resolveSubtraction]
+          [resolveBracketedExpressions]
+    where not
+        NewE [= E]
+    by
+        NewE
+end rule
+
+rule resolveAddition
+    replace [expression]
+        N1 [number] + N2 [number]
+    by
+        N1 [+ N2]
+end rule
+
+rule resolveSubtraction
+    replace [expression]
+        N1 [number] - N2 [number]
+    by
+        N1 [- N2]
+end rule 
+
+rule resolveBracketedExpressions
+    replace [primary]
+        ( N [number] )
+    by
+        N
+end rule
+

topics/fl/txl/Makefile

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+test:
+	cp ../shared/factorial.txt factorial.fl
+	txl -newline factorial.fl