Adds CLR statement.

This fixes #18

manual.md

@@ -1369,6 +1369,19 @@ General Statements
   apostrophe will be ignored. This is
   analogous to REM in Atari BASIC.
 
+
+**Clears variables and free memory**  
+**CLR**
+
+  Clears all integer and floating-point
+  variables to 0, all strings to empty
+  strings and frees all memory
+  associated with arrays.
+
+  After `CLR` you can't access arrays
+  without allocating again with `DIM`.
+
+
 **Defines array with initial values**  
 **DATA _arr()_ [type] = n1,n2, / DA.**
 

src/basic.syn

@@ -665,6 +665,7 @@ PARSE_LINE_COMMAND:
         "PMHpos"  EXPR emit { TOK_PUSH_NUM, &HPOSP0, TOK_ADD, TOK_SADDR } "," EXPR emit TOK_POKE
         "Timer" emit { TOK_0, TOK_BYTE_POKE, 20, TOK_0, TOK_BYTE_POKE, 19 }
         "DLi" DLI_COMMAND
+        "CLR" emit { TOK_NUM, &CLEAR_DATA, TOK_USR_ADDR, TOK_USR_CALL }
 
 PARSE_LINE_ASSIGN:
         VAR_WORD_SAVE                  EQUAL EXPR emit TOK_VAR_STORE E_POP_VAR

src/interp/clearmem.asm

@@ -28,7 +28,7 @@
 ; ------------
 
         .export         clear_data, alloc_array, mem_set, err_nomem, saved_cpu_stack
-        .export         compiled_num_vars
+        .export         compiled_num_vars, CLEAR_DATA
 
         .import         putc
         .importzp       var_page, tmp1, tmp2, array_ptr
@@ -39,6 +39,9 @@ MEMTOP=         $2E5
         ; Allocation size
 alloc_size=     tmp1
 
+        ; Uppercase to export as FastBasic symbol
+CLEAR_DATA = clear_data
+
 ;----------------------------------------------------------
 ; Following routines are part of the runtime
         .segment        "RUNTIME"

src/parse.asm

@@ -42,7 +42,7 @@
         .importzp       DEGFLAG, DEGFLAG_DEG, DEGFLAG_RAD
         .import         EXE_END, saved_cpu_stack, PMGMODE, PMGBASE
         ; Interpreted commands
-        .import         SOUND_OFF
+        .import         CLEAR_DATA, SOUND_OFF
         ; From errors.asm
         .import         error_msg_list
         .importzp       ERR_PARSE, ERR_NO_ELOOP, ERR_LABEL, ERR_TOO_LONG

testsuite/tests/stmt-clr.bas

@@ -0,0 +1,25 @@
+' Test for statement "CLR"
+? "Start"
+
+n = 0
+f = fre()
+
+' Dim inside a PROC to call multiple times
+proc dima
+  ? "---- DIM "; n; " ----"
+  ? "Before: "; f-fre()
+  dim a(n)
+  ? "After: "; f-fre()
+endproc
+
+n=10 : exec dima
+n=10 : exec dima
+
+? "---- CLR ----"
+clr
+
+? f, n, adr(a)
+
+f = fre()
+n=100 : exec dima
+

testsuite/tests/stmt-clr.chk

@@ -0,0 +1,15 @@
+Name: Test statement "CLR"
+Test: run
+Output:
+Start
+---- DIM 10 ----
+Before: 0
+After: 22
+---- DIM 10 ----
+Before: 22
+After: 44
+---- CLR ----
+0         0         0
+---- DIM 100 ----
+Before: 0
+After: 202