Adds MSET statement to clear/set memory areas.

Makefile

@@ -140,6 +140,7 @@ COMMON_AS_SRC=\
     src/interp/lnot.asm\
     src/interp/lor.asm\
     src/interp/move.asm\
+    src/interp/mset.asm\
     src/interp/mul.asm\
     src/interp/negax.asm\
     src/interp/nmove.asm\

manual.md

@@ -1381,6 +1381,23 @@ modify memory. Use with care.
       NEXT I
 
 
+**Sets memory to a value**  
+**MSET _address_, _length_, _value_ / MS.**  
+
+  Writes _length_ bytes in memory at
+  given _address_ with _value_.
+
+  This is useful to clear graphics
+  or P/M data, or simply to set an
+  string to a repeated value.
+
+  `MSET a, b, c` is equivalent to:
+
+      FOR I=0 to b-1
+        POKE a+I, c
+      NEXT I
+
+
 **Writes a byte to memory**  
 **POKE _address_, _value_ / P.**
 

src/basic.syn

@@ -39,7 +39,7 @@ TOKENS {
  # Convert from int to bool
  TOK_COMP_0
  # Low level statements
- TOK_POKE, TOK_DPOKE, TOK_MOVE, TOK_NMOVE, TOK_INC, TOK_DEC
+ TOK_POKE, TOK_DPOKE, TOK_MOVE, TOK_NMOVE, TOK_MSET, TOK_INC, TOK_DEC
  # Graphic support statements
  TOK_GRAPHICS, TOK_PLOT, TOK_DRAWTO
  # Print statements
@@ -553,6 +553,7 @@ PARSE_LINE_COMMAND:
         "CLS" IO_CHAN_OPT_NOCOMMA emit TOK_BYTE emit CLS emit TOK_PUT
         "Poke"  EXPR_2 emit TOK_POKE
         "Dpoke" EXPR_2 emit TOK_DPOKE
+        "MSet"  EXPR_2 "," EXPR emit TOK_MSET
         "Move"  EXPR_2 "," EXPR emit TOK_MOVE
         "-move" EXPR_2 "," EXPR emit TOK_NMOVE
         "DO" emit LT_DO_LOOP E_PUSH_LT

src/clearmem.asm

@@ -27,7 +27,7 @@
 ; Clear Memory
 ; ------------
 
-        .export         clear_data, alloc_array
+        .export         clear_data, alloc_array, mem_set
 
         .import         move_dwn_src, move_dwn_dst, move_dwn, putc, EXE_END
         .importzp       mem_end, var_buf, tmp1, tmp2, array_ptr, var_count
@@ -83,11 +83,14 @@ alloc_size=     tmp1
         bcs     err_nomem
 
         ; Clears memory from (tmp2) of (alloc_size) size
+        ldy     #0      ; Value to set
+
+::mem_set:
         txa     ; X = (alloc_size+1)
         clc
         adc     tmp2+1
         sta     tmp2+1
-        lda     #0
+        tya
         inx
         ldy     alloc_size
         beq     nxt

src/interp/mset.asm

@@ -0,0 +1,61 @@
+;
+; FastBasic - Fast basic interpreter for the Atari 8-bit computers
+; Copyright (C) 2017,2018 Daniel Serpell
+;
+; This program is free software; you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation, either version 2 of the License, or
+; (at your option) any later version.
+;
+; This program is distributed in the hope that it will be useful,
+; but WITHOUT ANY WARRANTY; without even the implied warranty of
+; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+; GNU General Public License for more details.
+;
+; You should have received a copy of the GNU General Public License along
+; with this program.  If not, see <http://www.gnu.org/licenses/>
+;
+; In addition to the permissions in the GNU General Public License, the
+; authors give you unlimited permission to link the compiled version of
+; this file into combinations with other programs, and to distribute those
+; combinations without any restriction coming from the use of this file.
+; (The General Public License restrictions do apply in other respects; for
+; example, they cover modification of the file, and distribution when not
+; linked into a combine executable.)
+
+
+; MSET: sets a range of memory to a value
+; ---------------------------------------
+
+        ; From interpreter.asm
+        .import         stack_l, stack_h, pop_stack_3
+        .import         mem_set
+        .importzp       tmp1, tmp2
+
+        .include "atari.inc"
+
+        .segment        "RUNTIME"
+
+.proc   EXE_MSET
+        pha             ; Store value to set into stack
+
+        lda     stack_l, y
+        sta     tmp1
+        ldx     stack_h, y
+
+        lda     stack_l+1, y
+        sta     tmp2
+        lda     stack_h+1, y
+        sta     tmp2+1
+
+        pla             ; Recover value to set into Y
+        tay
+        jsr     mem_set
+
+        jmp     pop_stack_3
+.endproc
+
+        .include "../deftok.inc"
+        deftoken "MSET"
+
+; vi:syntax=asm_ca65