parser: implement switch statement

A VM instruction `EqualSet` has been added to preserve the left
operand on the stack in case of failure, to allow efficient
multiple tests on the same value.
Both the pattern 'if/else if' and the classical case clauses have
been implemented.

1 files changed, 1 insertions, 0 deletions

diff --git a/lang/token.go b/lang/token.go
index 880f474..95a1be5 100644
--- a/lang/token.go
+++ b/lang/token.go
@@ -109,6 +109,7 @@ const (
 	JumpFalse
 	JumpSetFalse
 	JumpSetTrue
+	EqualSet
 )
 
 func (t TokenId) IsKeyword() bool   { return t >= Break && t <= Var }