* generic/tclCompCmds.c (TclCompileLreplaceCmd): Added a compilation

	strategy for [lreplace] that tackles the cases which are equivalent to
	a static [lrange].

1 files changed, 124 insertions, 0 deletions

diff --git a/generic/tclCompCmds.c b/generic/tclCompCmds.c
index c96f05c..5b7e0a5 100644
--- a/generic/tclCompCmds.c
+++ b/generic/tclCompCmds.c
@@ -3405,6 +3405,130 @@ TclCompileLrangeCmd(
 /*
  *----------------------------------------------------------------------
  *
+ * TclCompileLreplaceCmd --
+ *
+ *	How to compile the "lreplace" command. We only bother with the case
+ *	where there are no elements to insert and where both the 'first' and
+ *	'last' arguments are constant and one can be deterined to be at the
+ *	end of the list. (This is the case that could also be written with
+ *	"lrange".)
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+TclCompileLreplaceCmd(
+    Tcl_Interp *interp,		/* Tcl interpreter for context. */
+    Tcl_Parse *parsePtr,	/* Points to a parse structure for the
+				 * command. */
+    Command *cmdPtr,		/* Points to defintion of command being
+				 * compiled. */
+    CompileEnv *envPtr)		/* Holds the resulting instructions. */
+{
+    Tcl_Token *tokenPtr, *listTokenPtr;
+    DefineLineInformation;	/* TIP #280 */
+    Tcl_Obj *tmpObj;
+    int idx1, idx2, result, guaranteedDropAll = 0;
+
+    if (parsePtr->numWords != 4) {
+	return TCL_ERROR;
+    }
+    listTokenPtr = TokenAfter(parsePtr->tokenPtr);
+
+    /*
+     * Parse the first index. Will only compile if it is constant and not an
+     * _integer_ less than zero (since we reserve negative indices here for
+     * end-relative indexing).
+     */
+
+    tokenPtr = TokenAfter(listTokenPtr);
+    if (tokenPtr->type != TCL_TOKEN_SIMPLE_WORD) {
+	return TCL_ERROR;
+    }
+    tmpObj = Tcl_NewStringObj(tokenPtr[1].start, tokenPtr[1].size);
+    result = TclGetIntFromObj(NULL, tmpObj, &idx1);
+    if (result == TCL_OK) {
+	if (idx1 < 0) {
+	    result = TCL_ERROR;
+	}
+    } else {
+	result = TclGetIntForIndexM(NULL, tmpObj, -2, &idx1);
+	if (result == TCL_OK && idx1 > -2) {
+	    result = TCL_ERROR;
+	}
+    }
+    TclDecrRefCount(tmpObj);
+    if (result != TCL_OK) {
+	return TCL_ERROR;
+    }
+
+    /*
+     * Parse the second index. Will only compile if it is constant and not an
+     * _integer_ less than zero (since we reserve negative indices here for
+     * end-relative indexing).
+     */
+
+    tokenPtr = TokenAfter(tokenPtr);
+    if (tokenPtr->type != TCL_TOKEN_SIMPLE_WORD) {
+	return TCL_ERROR;
+    }
+    tmpObj = Tcl_NewStringObj(tokenPtr[1].start, tokenPtr[1].size);
+    result = TclGetIntFromObj(NULL, tmpObj, &idx2);
+    if (result == TCL_OK) {
+	if (idx2 < 0) {
+	    result = TCL_ERROR;
+	}
+    } else {
+	result = TclGetIntForIndexM(NULL, tmpObj, -2, &idx2);
+	if (result == TCL_OK && idx2 > -2) {
+	    result = TCL_ERROR;
+	}
+    }
+    TclDecrRefCount(tmpObj);
+    if (result != TCL_OK) {
+	return TCL_ERROR;
+    }
+
+    /*
+     * Sanity check: can only issue when we're removing a range at one or
+     * other end of the list. If we're at one end or the other, convert the
+     * indices into the equivalent for an [lrange].
+     */
+
+    if (idx1 == 0) {
+	if (idx2 == -2) {
+	    guaranteedDropAll = 1;
+	}
+	idx1 = idx2 + 1;
+	idx2 = -2;
+    } else if (idx2 == -2) {
+	idx2 = idx1 - 1;
+	idx1 = 0;
+    } else {
+	return TCL_ERROR;
+    }
+
+    /*
+     * Issue instructions. It's not safe to skip doing the LIST_RANGE, as
+     * we've not proved that the 'list' argument is really a list. Not that it
+     * is worth trying to do that given current knowledge.
+     */
+
+    CompileWord(envPtr, listTokenPtr, interp, 1);
+    if (guaranteedDropAll) {
+	TclEmitOpcode(		INST_LIST_LENGTH,		envPtr);
+	TclEmitOpcode(		INST_POP,			envPtr);
+	PushLiteral(envPtr, "", 0);
+    } else {
+	TclEmitInstInt4(	INST_LIST_RANGE_IMM, idx1,	envPtr);
+	TclEmitInt4(		idx2,				envPtr);
+    }
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * TclCompileLsetCmd --
  *
  *	Procedure called to compile the "lset" command.