examples: bistromathic: fix location tracking

[Akim Demaille]

commit 493359b75815df852195b1517f868743ba7998f7
Author: Akim Demaille <address@hidden>
Date:   Sun Feb 2 08:59:54 2020 +0100

    examples: bistromathic: fix location tracking
    
    * examples/c/bistromathic/scan.l (LOCATION_STEP): New.
    Use to properly ignore blanks.
    * examples/c/bistromathic/bistromathic.test: Check that case.

diff --git a/examples/c/bistromathic/bistromathic.test 
b/examples/c/bistromathic/bistromathic.test
index 4d19c98b..89ebcb40 100755
--- a/examples/c/bistromathic/bistromathic.test
+++ b/examples/c/bistromathic/bistromathic.test
@@ -46,3 +46,8 @@ cat >input <<EOF
 *
 EOF
 run 0 "err: 1.1: syntax error expected end of file or - or ( or end of line or 
double precision number or function or variable before *"
+
+cat >input <<EOF
+1 + 2 * * 3
+EOF
+run 0 "err: 1.9: syntax error expected - or ( or double precision number or 
function or variable before *"
diff --git a/examples/c/bistromathic/scan.l b/examples/c/bistromathic/scan.l
index c5f57c1e..e04cbc19 100644
--- a/examples/c/bistromathic/scan.l
+++ b/examples/c/bistromathic/scan.l
@@ -13,13 +13,19 @@
   // Each time a rule is matched, advance the end cursor/position.
 #define YY_USER_ACTION                          \
   yylloc->last_column += yyleng;
+
+  // Move the first position onto the last.
+#define LOCATION_STEP()                         \
+  do {                                          \
+    yylloc->first_line = yylloc->last_line;     \
+    yylloc->first_column = yylloc->last_column; \
+  } while (0)
 %}
 
 %%
 %{
   // Each time yylex is called, move the head position to the end one.
-  yylloc->first_line = yylloc->last_line;
-  yylloc->first_column = yylloc->last_column;
+  LOCATION_STEP ();
 %}
  /* Rules.  */
 
@@ -52,7 +58,7 @@
 "\n"     yylloc->last_line++; yylloc->last_column = 1; return TOK_EOL;
 
  /* Ignore white spaces. */
-[ \t]+   continue;
+[ \t]+   LOCATION_STEP (); continue;
 
 <<EOF>>  return TOK_EOF;