diff --git a/R/optObj_cplexAPIClass.R b/R/optObj_cplexAPIClass.R
index 8f6d0edc40cdbbfb88747b9684cde463a6d5be21..3618af1db62558e595ebff43eebf966b7133a351 100644
--- a/R/optObj_cplexAPIClass.R
+++ b/R/optObj_cplexAPIClass.R
@@ -392,7 +392,7 @@ setMethod("addRowsToProb", signature(lp = "optObj_cplexAPI"),
 
         cptype = character(length(type))
         for (l in seq(along = type)) {
-            cptype[l] <- switch(type[l],
+            cptype[l] <- switch(EXPR = type[l],
                 "L" = { "G" },
                 "U" = { "L" },
                 "D" = { "R" },
@@ -737,7 +737,7 @@ setMethod("loadLPprob", signature(lp = "optObj_cplexAPI"),
         stopifnot(is(mat, "Matrix"))
 
         crtype <- sapply(rtype,
-                         function(x) switch(x,
+                         function(x) switch(EXPR = x,
                                             "L" = { "G" },
                                             "U" = { "L" },
                                             "D" = { "R" },
@@ -898,7 +898,7 @@ setMethod("solveLp", signature(lp = "optObj_cplexAPI"),
     function(lp) {
 
         out <- FALSE
-        switch(lp@method,
+        switch(EXPR = lp@method,
             "primopt" = {
                 out <- cplexAPI::primoptCPLEX(lp@oobj@env, lp@oobj@lp)
             },
diff --git a/R/optObj_glpkAPIClass.R b/R/optObj_glpkAPIClass.R
index 325f47eedd25ec721737988bcabd388e9439054a..2fdb9d2d2894dd055ff055994bf56ad0aad8bb5b 100644
--- a/R/optObj_glpkAPIClass.R
+++ b/R/optObj_glpkAPIClass.R
@@ -112,7 +112,7 @@ setMethod("setSolverParm", signature(lp = "optObj_glpkAPI"),
         parm <- sapply(names(solverParm), function(x) eval(parse(text = x)))
         val  <- unlist(solverParm)
 
-        switch(lp@method,
+        switch(EXPR=lp@method,
             "interior" = {
                 glpkAPI::setInteriorParmGLPK(parm, val)
             },
@@ -135,7 +135,7 @@ setMethod("getSolverParm", signature(lp = "optObj_glpkAPI"),
 
         out <- FALSE
 
-        switch(lp@method,
+        switch(EXPR=lp@method,
             "interior" = {
                 out <- glpkAPI::getInteriorParmGLPK()
             },
@@ -329,7 +329,7 @@ setMethod("addRowsToProb", signature(lp = "optObj_glpkAPI"),
         ord <- glpkAPI::addRowsGLPK(lp@oobj, length(i))
         gtype = integer(length(type))
         for (k in seq(along = i)) {
-            gtype[k] <- switch(type[k],
+            gtype[k] <- switch(EXPR = type[k],
                                "F" = { glpkAPI::GLP_FR },
                                "L" = { glpkAPI::GLP_LO },
                                "U" = { glpkAPI::GLP_UP },
@@ -576,7 +576,7 @@ setMethod("loadLPprob", signature(lp = "optObj_glpkAPI"),
         stopifnot(is(mat, "Matrix"))
 
         crtype <- sapply(rtype,
-                         function(x) switch(x,
+                         function(x) switch(EXPR = x,
                                             "F" = { glpkAPI::GLP_FR },
                                             "L" = { glpkAPI::GLP_LO },
                                             "U" = { glpkAPI::GLP_UP },
@@ -610,7 +610,7 @@ setMethod("loadLPprob", signature(lp = "optObj_glpkAPI"),
         # variable type
         if (!is.null(ctype)) {
             cctype <- sapply(ctype,
-                             function(x) switch(x,
+                             function(x) switch(EXPR = x,
                                                 "C" = { glpkAPI::GLP_CV },
                                                 "I" = { glpkAPI::GLP_IV },
                                                 "B" = { glpkAPI::GLP_BV },
@@ -689,7 +689,7 @@ setMethod("solveLp", signature(lp = "optObj_glpkAPI"),
 #                #print(basis)
 #            }
 #        }
-        switch(lp@method,
+        switch(EXPR = lp@method,
             "interior" = {
                 out <- glpkAPI::solveInteriorGLPK(lp@oobj)
             },
@@ -715,7 +715,7 @@ setMethod("getObjVal", signature(lp = "optObj_glpkAPI"),
 
     function(lp) {
 
-        switch(lp@method,
+        switch(EXPR = lp@method,
             "interior" = {
                 out <- glpkAPI::getObjValIptGLPK(lp@oobj)
             },
@@ -756,7 +756,7 @@ setMethod("getSolStat", signature(lp = "optObj_glpkAPI"),
 
     function(lp) {
 
-        switch(lp@method,
+        switch(EXPR = lp@method,
             "interior" = {
                 out <- glpkAPI::getSolStatIptGLPK(lp@oobj)
             },
@@ -779,7 +779,7 @@ setMethod("getFluxDist", signature(lp = "optObj_glpkAPI"),
 
     function(lp) {
 
-        switch(lp@method,
+        switch(EXPR = lp@method,
             "interior" = {
                 out <- glpkAPI::getColsPrimIptGLPK(lp@oobj)
             },
@@ -802,7 +802,7 @@ setMethod("getColPrim", signature(lp = "optObj_glpkAPI", j = "numeric"),
 
     function(lp, j) {
 
-        switch(lp@method,
+        switch(EXPR = lp@method,
             "interior" = {
                 out <- glpkAPI::getColPrimIptGLPK(lp@oobj, j)
             },
@@ -838,7 +838,7 @@ setMethod("writeProb", signature(lp = "optObj_glpkAPI", fname = "character"),
 
     function(lp, fname, ff = "lp", ...) {
 
-        switch(ff,
+        switch(EXPR = ff,
             "lp"  = {
                 fl <- glpkAPI::writeLPGLPK(lp@oobj, fname = fname)
             },
@@ -866,7 +866,7 @@ setMethod("readProb", signature(lp = "optObj_glpkAPI", fname = "character"),
 
     function(lp, fname, ff = "lp", ...) {
 
-        switch(ff,
+        switch(EXPR = ff,
             "lp"  = {
                 fl <- glpkAPI::readLPGLPK(lp@oobj, fname = fname)
             },
diff --git a/R/optObj_lpSolveAPIClass.R b/R/optObj_lpSolveAPIClass.R
index 2ce80c52a28819e9312cb3d12f5e3874e94a9ab4..37505f2142da82d2bfd6e946be427253ceba81a7 100644
--- a/R/optObj_lpSolveAPIClass.R
+++ b/R/optObj_lpSolveAPIClass.R
@@ -292,7 +292,7 @@ setMethod("addRowsToProb", signature(lp = "optObj_lpSolveAPI"),
 
         stopifnot(length(lb) == length(ub))
         for (k in seq(along = i)) {
-            ltype <- switch(type[k],
+            ltype <- switch(EXPR = type[k],
                             "L" = { 2 },
                             "U" = { 1 },
                             "D" = { 1 },
@@ -494,7 +494,7 @@ setMethod("loadLPprob", signature(lp = "optObj_lpSolveAPI"),
         # problem size is already specified in optObj_lpSolveAPI constructor
 
         crtype <- sapply(rtype,
-                         function(x) switch(x,
+                         function(x) switch(EXPR = x,
                                             "L" = { 2 },
                                             "U" = { 1 },
                                             "D" = { 1 },