1 files changed, 149 insertions, 0 deletions
diff --git a/src/runtime/fscan.r b/src/runtime/fscan.r
new file mode 100644
index 0000000..8cba731
--- /dev/null
+++ b/src/runtime/fscan.r
@@ -0,0 +1,149 @@
+/*
+ * File: fscan.r
+ *  Contents: move, pos, tab.
+ */
+
+"move(i) - move &pos by i, return substring of &subject spanned."
+" Reverses effects if resumed."
+
+function{0,1+} move(i)
+
+   if !cnv:C_integer(i) then
+      runerr(101,i)
+
+   abstract {
+      return string
+      }
+
+   body {
+      register C_integer j;
+      C_integer oldpos;
+
+      /*
+       * Save old &pos.  Local variable j holds &pos before the move.
+       */
+      oldpos = j = k_pos;
+
+      /*
+       * If attempted move is past either end of the string, fail.
+       */
+      if (i + j <= 0 || i + j > StrLen(k_subject) + 1)
+         fail;
+
+      /*
+       * Set new &pos.
+       */
+      k_pos += i;
+      EVVal(k_pos, E_Spos);
+
+      /*
+       * Make sure i >= 0.
+       */
+      if (i < 0) {
+         j += i;
+         i = -i;
+         }
+
+      /*
+       * Suspend substring of &subject that was moved over.
+       */
+      suspend string(i, StrLoc(k_subject) + j - 1);
+
+      /*
+       * If move is resumed, restore the old position and fail.
+       */
+      if (oldpos > StrLen(k_subject) + 1)
+         runerr(205, kywd_pos);
+      else {
+         k_pos = oldpos;
+         EVVal(k_pos, E_Spos);
+         }
+
+      fail;
+      }
+end
+
+
+"pos(i) - test if &pos is at position i in &subject."
+
+function{0,1} pos(i)
+
+   if !cnv:C_integer(i) then
+      runerr(101, i)
+
+   abstract {
+      return integer
+      }
+   body {
+      /*
+       * Fail if &pos is not equivalent to i, return i otherwise.
+       */
+      if ((i = cvpos(i, StrLen(k_subject))) != k_pos)
+         fail;
+      return C_integer i;
+      }
+end
+
+
+"tab(i) - set &pos to i, return substring of &subject spanned."
+"Reverses effects if resumed."
+
+function{0,1+} tab(i)
+
+   if !cnv:C_integer(i) then
+      runerr(101, i);
+
+   abstract {
+      return string
+      }
+
+   body {
+      C_integer j, t, oldpos;
+
+      /*
+       * Convert i to an absolute position.
+       */
+      i = cvpos(i, StrLen(k_subject));
+      if (i == CvtFail)
+         fail;
+
+      /*
+       * Save old &pos.  Local variable j holds &pos before the tab.
+       */
+      oldpos = j = k_pos;
+
+      /*
+       * Set new &pos.
+       */
+      k_pos = i;
+      EVVal(k_pos, E_Spos);
+
+      /*
+       *  Make i the length of the substring &subject[i:j]
+       */
+      if (j > i) {
+         t = j;
+         j = i;
+         i = t - j;
+         }
+      else
+         i = i - j;
+
+      /*
+       * Suspend the portion of &subject that was tabbed over.
+       */
+      suspend string(i, StrLoc(k_subject) + j - 1);
+
+      /*
+       * If tab is resumed, restore the old position and fail.
+       */
+      if (oldpos > StrLen(k_subject) + 1)
+         runerr(205, kywd_pos);
+      else {
+         k_pos = oldpos;
+         EVVal(k_pos, E_Spos);
+         }
+
+      fail;
+      }
+end