From 3db38b0d89e5efb6896d93e694e1d09f07a982b2 Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Thu, 12 Dec 2019 11:17:10 -0500
Subject: [PATCH] basic: add while command

---
 apps/basic/README.md      |  5 ++++-
 apps/basic/main.asm       | 32 ++++++++++++++++++++++++++++++--
 doc/blockdev.md           | 21 ++++++---------------
 doc/load-run-code.md      |  4 +---
 tools/emul/shell/glue.asm |  3 ++-
 5 files changed, 43 insertions(+), 22 deletions(-)

diff --git a/apps/basic/README.md b/apps/basic/README.md
index 8af3b08..9a6d705 100644
--- a/apps/basic/README.md
+++ b/apps/basic/README.md
@@ -126,11 +126,14 @@ specified as an argument. Errors out if line doesn't exist. Argument can be
 an expression. If invoked in direct mode, `run` must be called to actually
 run the line (followed by the next, and so on).
 
-`if <cond> <cmd>`: If specified condition is true, execute the rest of the
+`if <cond> <cmds>`: If specified condition is true, execute the rest of the
 line. Otherwise, do nothing. For example, `if 2>1 print 12` prints `12` and `if
 2<1 print 12` does nothing. The argument for this command is a "thruth
 expression".
 
+`while <cond> <cmds>`: As long as specified condition is true, execute specified
+commands repeatedly.
+
 `input [<prompt>]`: Prompts the user for a numerical value and puts that
 value in `A`. The prompted value is evaluated as an expression and then stored.
 The command takes an optional string literal parameter. If present, that string
diff --git a/apps/basic/main.asm b/apps/basic/main.asm
index f4559f7..a1f8ef2 100644
--- a/apps/basic/main.asm
+++ b/apps/basic/main.asm
@@ -267,14 +267,20 @@ basGOTO:
 	ld	(BAS_PNEXTLN), de
 	ret
 
-basIF:
+; evaluate truth condition at (HL) and set A to its value
+; Z for success (but not truth!)
+_basEvalCond:
 	push	hl	; --> lvl 1. original arg
 	ld	de, SCRATCHPAD
 	call	rdWord
 	ex	de, hl
 	call	parseTruth
 	pop	hl	; <-- lvl 1. restore
-	ret	nz
+	ret
+
+basIF:
+	call	_basEvalCond
+	ret	nz	; error
 	or	a
 	ret	z
 	; expr is true, execute next
@@ -285,6 +291,26 @@ basIF:
 	ld	de, basCmds2
 	jp	basCallCmds
 
+basWHILE:
+	push	hl	; --> lvl 1
+	call	_basEvalCond
+	jr	nz, .stop	; error
+	or	a
+	jr	z, .stop
+	ret	z
+	; expr is true, execute next
+	; (HL) back to beginning of args, skip to next arg
+	call	toSepOrEnd
+	call	rdSep
+	ret	nz
+	ld	de, basCmds2
+	call	basCallCmds
+	pop	hl	; <-- lvl 1
+	jr	basWHILE
+.stop:
+	pop	hl	; <-- lvl 1
+	ret
+
 basINPUT:
 	; If our first arg is a string literal, spit it
 	call	spitQuoted
@@ -478,6 +504,8 @@ basCmds2:
 	.dw	basGOTO
 	.db	"if", 0
 	.dw	basIF
+	.db	"while", 0
+	.dw	basWHILE
 	.db	"input", 0
 	.dw	basINPUT
 	.db	"peek", 0
diff --git a/doc/blockdev.md b/doc/blockdev.md
index ddb0ad4..cf3d949 100644
--- a/doc/blockdev.md
+++ b/doc/blockdev.md
@@ -52,21 +52,12 @@ Let's try an example: You glue yourself a Collapse OS with a mmap starting at
 could do to copy memory around:
 
     > m=0xe000
-    > 10 getc
-    > 20 poke m a
-    > 30 m=m+1
-    > 40 if m<0xe004 goto 10 
-    > run
+    > while m<0xe004 getc:poke m a:m=m+1
     [enter "abcd"]
     > bsel 3
-    > clear
-    > 10 getb
-    > 20 puth a
-    > run
-    61> run
-    62> run
-    63> run
-    64> bseek 2
-    > run
-    63> run
+    > i=0
+    > while i<4 getb:puth a:i=i+1
+    61626364> bseek 2
+    > getb:puth a
+    63> getb:puth a
     64>
diff --git a/doc/load-run-code.md b/doc/load-run-code.md
index e0eb477..9766473 100644
--- a/doc/load-run-code.md
+++ b/doc/load-run-code.md
@@ -21,9 +21,7 @@ increase a number at memory address `0xa100`. First, compile it:
 Now, we'll send that code to address `0xa000`:
 
     > m=0xa000
-    > 10 getc
-    > 20 poke m a
-    > 30 if m<0xa008 goto 10
+    > while m<0xa008 getc:poke m a:m=m+1
     (resulting binary is 8 bytes long)
 
 Now, at this point, it's a bit delicate. To pipe your binary to your serial
diff --git a/tools/emul/shell/glue.asm b/tools/emul/shell/glue.asm
index 80b0c97..6bf7ee8 100644
--- a/tools/emul/shell/glue.asm
+++ b/tools/emul/shell/glue.asm
@@ -61,6 +61,7 @@
 .equ	STDIO_RAMSTART	BLOCKDEV_RAMEND
 .equ	STDIO_GETC	emulGetC
 .equ	STDIO_PUTC	emulPutC
+.equ	STDIO_BUFSIZE	0x40	; override
 .inc "stdio.asm"
 
 .equ	FS_RAMSTART	STDIO_RAMEND
@@ -70,7 +71,7 @@
 ; *** BASIC ***
 
 ; RAM space used in different routines for short term processing.
-.equ	SCRATCHPAD_SIZE	0x20
+.equ	SCRATCHPAD_SIZE	STDIO_BUFSIZE
 .equ	SCRATCHPAD	FS_RAMEND
 .inc "lib/util.asm"
 .inc "lib/ari.asm"