allow enabling Prism via flag or env var

Enable Prism using either --prism

    ruby --prism test.rb

or via env var

    RUBY_PRISM=1 ruby test.rb

1 files changed, 11 insertions, 0 deletions

diff --git a/prism/prism.h b/prism/prism.h
index 590cd74016..d55c4f2bfd 100644
--- a/prism/prism.h
+++ b/prism/prism.h
@@ -42,6 +42,17 @@
  */
 PRISM_EXPORTED_FUNCTION const char * pm_version(void);
 
+
+/**
+ * @private
+ *
+ * This is used to decide of the prism parser should be used.
+ *
+ * @retval  true       Use Prism to parse files
+ * @retval  false      Use standard parser
+ */
+bool *rb_ruby_prism_ptr(void);
+
 /**
  * Initialize a parser with the given start and end pointers.
  *