Added try .. then .. clause

M2/Macaulay2/d/binding.d

@@ -889,6 +889,10 @@ export bind(e:ParseTree,dictionary:Dictionary):void := (
 	  -- i.alternate = bindnewdictionary(i.alternate,dictionary);
 	  bind(i.alternate,dictionary);
 	  )
+     is i:TryThen do (
+	  bind(i.primary,dictionary);
+	  bind(i.sequel,dictionary);
+	  )
      is i:TryThenElse do (
 	  bind(i.primary,dictionary);
 	  bind(i.sequel,dictionary);

M2/Macaulay2/d/convertr.d

@@ -432,9 +432,10 @@ export convert(e:ParseTree):Code := (
 	  pos := treePosition(e);
 	  nd := nestingDepth(sym.frameID,token.dictionary);
 	  Code(localSymbolClosureCode(nd,sym,pos)))
-     is i:TryThenElse do Code(tryCode(convert(i.primary),convert(i.sequel),convert(i.alternate),treePosition(e)))
-     is i:TryElse do Code(tryCode(convert(i.primary),NullCode,convert(i.alternate),treePosition(e)))
-     is i:Try do Code(tryCode(convert(i.primary),NullCode,NullCode,treePosition(e)))
+    is i:TryThenElse do Code(tryCode(convert(i.primary), convert(i.sequel), convert(i.alternate), treePosition(e)))
+    is i:TryThen     do Code(tryCode(convert(i.primary), convert(i.sequel), NullCode,             treePosition(e)))
+    is i:TryElse     do Code(tryCode(convert(i.primary), NullCode,          convert(i.alternate), treePosition(e)))
+    is i:Try         do Code(tryCode(convert(i.primary), NullCode,          NullCode,             treePosition(e)))
      is i:Catch do Code(catchCode(convert(i.primary),treePosition(e)))
      is u:Postfix do Code(unaryCode(u.Operator.entry.postfix,convert(u.lhs),treePosition(e)))
      is d:dummy do dummyCode

M2/Macaulay2/d/evaluate.d

@@ -1474,14 +1474,11 @@ export evalraw(c:Code):Expr := (
 	  is c:globalSymbolClosureCode do return Expr(SymbolClosure(globalFrame,c.symbol))
 	  is c:threadSymbolClosureCode do return Expr(SymbolClosure(threadFrame,c.symbol))
 	  is c:tryCode do (
-	       p := tryEval(c.code);
-	       if tryEvalSuccess
-	       then (
-		   when p is Error do p
-		   else if c.thenClause == NullCode then p
-		   else eval(c.thenClause))
-	       else (
-		   eval(c.elseClause)))
+	      ret := tryEval(c.code);
+	      if tryEvalSuccess then
+	      when ret is Error do ret
+	      else if c.thenClause == NullCode then ret   else eval(c.thenClause)
+	      else if c.elseClause == NullCode then nullE else eval(c.elseClause))
 	  is c:catchCode do (
 	       p := eval(c.code);
 	       when p is err:Error do if err.message == throwMessage then err.value else p

M2/Macaulay2/d/parse.d

@@ -127,9 +127,10 @@ export For := {+ forToken:Token, variable:ParseTree, inClause:ParseTree, fromCla
 export WhileDo := {+ whileToken:Token, predicate:ParseTree, dotoken:Token, doClause:ParseTree};
 export WhileList := {+ whileToken:Token, predicate:ParseTree, listtoken:Token, listClause:ParseTree};
 export WhileListDo := {+ whileToken:Token, predicate:ParseTree, listtoken:Token, listClause:ParseTree, dotoken:Token, doClause:ParseTree };
-export TryElse := {+ tryToken:Token, primary:ParseTree, elseToken:Token, alternate:ParseTree};
 export TryThenElse := {+ tryToken:Token, primary:ParseTree, thenToken:Token, sequel:ParseTree, elseToken:Token, alternate:ParseTree};
-export Try := {+ tryToken:Token, primary:ParseTree};
+export TryThen     := {+ tryToken:Token, primary:ParseTree, thenToken:Token, sequel:ParseTree};
+export TryElse     := {+ tryToken:Token, primary:ParseTree,                                    elseToken:Token, alternate:ParseTree};
+export Try         := {+ tryToken:Token, primary:ParseTree};
 export Catch := {+ catchToken:Token, primary:ParseTree};
 export IfThen := {+ ifToken:Token, predicate:ParseTree, thenclause:ParseTree };
 export IfThenElse := {+ ifToken:Token, predicate:ParseTree, thenclause:ParseTree, elseClause:ParseTree};
@@ -150,7 +151,7 @@ export ParseTree := (
      Token or Adjacent or Binary or Unary or Postfix or Parentheses 
      or EmptyParentheses or IfThen or IfThenElse
      or Quote or GlobalQuote or ThreadQuote or LocalQuote
-     or TryThenElse or TryElse or Try or Catch or WhileDo or For or WhileList or WhileListDo or Arrow or New or dummy );
+     or TryThenElse or TryThen or TryElse or Try or Catch or WhileDo or For or WhileList or WhileListDo or Arrow or New or dummy );
 
 
 -- Code

M2/Macaulay2/d/parser.d

@@ -487,9 +487,7 @@ export unarytry(tryToken:Token,file:TokenFile,prec:int,obeylines:bool):ParseTree
 	       elseClause := parse(file,elseW.parse.unaryStrength,obeylines);
 	       if elseClause == errorTree then return errorTree;
 	       accumulate(ParseTree(TryThenElse(tryToken,primary,thenToken,thenClause,elseToken,elseClause)),file,prec,obeylines))
-	  else (
-	       printErrorMessage(tryToken,"syntax error : expected 'else' to match this 'try'");
-	       errorTree))
+	  else accumulate(ParseTree(TryThen(tryToken,primary,thenToken,thenClause)),file,prec,obeylines))
      else accumulate(ParseTree(Try(tryToken,primary)),file,prec,obeylines));
 export unarycatch(catchToken:Token,file:TokenFile,prec:int,obeylines:bool):ParseTree := (
      primary := parse(file,catchToken.word.parse.unaryStrength,obeylines);
@@ -532,6 +530,7 @@ export treePosition(e:ParseTree):Position := (
 	  is ee:EmptyParentheses do return position(ee.left)
      	  is i:IfThen do return position(i.ifToken)
 	  is i:TryThenElse do return position(i.tryToken)
+	  is i:TryThen do return position(i.tryToken)
 	  is i:TryElse do return position(i.tryToken)
 	  is i:Try do return position(i.tryToken)
 	  is i:Catch do return position(i.catchToken)
@@ -564,9 +563,10 @@ export size(e:ParseTree):int := (
      is x:EmptyParentheses do Ccode(int,"sizeof(*",x,")") + size(x.left) + size(x.right)
      is x:IfThen do Ccode(int,"sizeof(*",x,")") + size(x.ifToken) + size(x.predicate) + size(x.thenclause)
      is x:IfThenElse do Ccode(int,"sizeof(*",x,")") + size(x.ifToken) + size(x.predicate) + size(x.thenclause) + size(x.elseClause)
-     is x:TryThenElse do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary) + size(x.thenToken) + size(x.sequel) + size(x.elseToken) + size(x.alternate)
-     is x:TryElse do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary) + size(x.elseToken) + size(x.alternate)
-     is x:Try do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary)
+    is x:TryThenElse do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary) + size(x.thenToken) + size(x.sequel) + size(x.elseToken) + size(x.alternate)
+    is x:TryThen     do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary) + size(x.thenToken) + size(x.sequel)
+    is x:TryElse     do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary)                                      + size(x.elseToken) + size(x.alternate)
+    is x:Try         do Ccode(int,"sizeof(*",x,")") + size(x.tryToken) + size(x.primary)
      is x:Catch do Ccode(int,"sizeof(*",x,")") + size(x.catchToken) + size(x.primary)
      is x:For do Ccode(int,"sizeof(*",x,")")+ size(x.forToken) + size(x.variable) + size(x.inClause) + size(x.fromClause) + size(x.toClause) + size(x.whenClause) + size(x.listClause) + size(x.doClause)
      is x:WhileDo do Ccode(int,"sizeof(*",x,")") + size(x.whileToken) + size(x.predicate) + size(x.dotoken) + size(x.doClause)

M2/Macaulay2/m2/basictests/A01.m2

@@ -55,11 +55,15 @@ assert( not not true )
 assert( not  true === false )
 assert( not  false === true )
 
--- test try
-assert( try error "" else true )
+-- test try .. then .. else clauses
+assert( true === try 1/0 then false else true )
+assert( null === try 1/0 then false )
+assert( true === try 1/0 else true )
+assert( null === try 1/0 )
+assert( try true then true else false )
 assert( try true else false )
+assert( try true then true )
 assert( try true )
-assert( null === try error "" )
 --i = 5
 --try i := 6 else i :=7
 --assert(i === 5)

M2/Macaulay2/packages/Macaulay2Doc/ov_language.m2

@@ -745,6 +745,10 @@ document {
      PARA{},
      "The clause '", TT "then y", "' may be omitted, in which case the return value is the value returned by ", TT "x", ", if there is no error or alarm.",
      PARA{},
+     "The clause '", TT "else z", "' may be omitted,
+     in which case the return value is the value returned by ", TT "y", ",
+     unless an error or alarm occurs, in which case ", TO "null", " is returned.",
+     PARA{},
      "The clauses '", TT "then y else z", "' may both be omitted, in which case the return value is the value returned by ", TT "x", ", unless an error or
      alarm occurs, in which case ", TO "null", " is returned.",
      PARA{},