Fixed how cmake handles the openmm version

CMakeLists.txt

@@ -8,17 +8,23 @@ PROJECT(OpenMMNonbondedSlicing VERSION 0.2.1)
 
 IF(DEFINED ENV{CONDA_PREFIX})
     SET(OPENMM_DIR $ENV{CONDA_PREFIX} CACHE PATH "Where OpenMM is installed")
+    EXECUTE_PROCESS(
+        COMMAND conda list ^openmm\\b
+        OUTPUT_VARIABLE CONDA_OPENMM_VERSION
+    )
+    IF (NOT CONDA_OPENMM_VERSION)
+        MESSAGE(FATAL_ERROR "OpenMM conda package not found. Please install OpenMM with conda.")
+    ENDIF(NOT CONDA_OPENMM_VERSION)
+    STRING(REGEX REPLACE "[^\\.]+([0-9]+\\.[0-9]+).*" "\\1" CONDA_OPENMM_VERSION "${CONDA_OPENMM_VERSION}")
+    SET(OPENMM_VERSION ${CONDA_OPENMM_VERSION} CACHE STRING "OpenMM version")
+ELSE(DEFINED ENV{CONDA_PREFIX})
 ENDIF(DEFINED ENV{CONDA_PREFIX})
 
-EXECUTE_PROCESS(
-    COMMAND conda list ^openmm\\b
-    OUTPUT_VARIABLE OPENMM_VERSION
-)
-IF (NOT OPENMM_VERSION)
-    MESSAGE(FATAL_ERROR "OpenMM conda package not found. Please install OpenMM with conda.")
-ENDIF(NOT OPENMM_VERSION)
-STRING(REGEX REPLACE ".* ([0-9]+)\\.[0-9]+\\.[0-9]+.*" "\\1" OPENMM_VERSION_MAJOR "${OPENMM_VERSION}")
-STRING(REGEX REPLACE ".* [0-9]+\\.([0-9]+)\\.[0-9]+.*" "\\1" OPENMM_VERSION_MINOR "${OPENMM_VERSION}")
+MESSAGE(STATUS "OpenMM version: ${OPENMM_VERSION}")
+STRING(REGEX REPLACE "^([0-9]+)\\.[0-9]+.*" "\\1" OPENMM_VERSION_MAJOR "${OPENMM_VERSION}")
+STRING(REGEX REPLACE "^[0-9]+\\.([0-9]+).*" "\\1" OPENMM_VERSION_MINOR "${OPENMM_VERSION}")
+MESSAGE(STATUS "OpenMM major version: ${OPENMM_VERSION_MAJOR}")
+MESSAGE(STATUS "OpenMM minor version: ${OPENMM_VERSION_MINOR}")
 ADD_COMPILE_DEFINITIONS(OPENMM_VERSION_MAJOR=${OPENMM_VERSION_MAJOR})
 ADD_COMPILE_DEFINITIONS(OPENMM_VERSION_MINOR=${OPENMM_VERSION_MINOR})