From: rich Date: Tue, 25 Sep 2007 21:46:20 +0000 (+0000) Subject: /MOD as primitive to replace / and MOD X-Git-Url: http://git.annexia.org/?a=commitdiff_plain;h=d4569e32354ba32b3aa02ed69b1e710e97aa5b8b;p=jonesforth.git /MOD as primitive to replace / and MOD Removed ., now in FORTH. --- diff --git a/jonesforth.S b/jonesforth.S index 7b6a757..6dccceb 100644 --- a/jonesforth.S +++ b/jonesforth.S @@ -1,7 +1,7 @@ /* A sometimes minimal FORTH compiler and tutorial for Linux / i386 systems. -*- asm -*- By Richard W.M. Jones http://annexia.org/forth This is PUBLIC DOMAIN (see public domain release statement below). - $Id: jonesforth.S,v 1.30 2007-09-25 09:50:54 rich Exp $ + $Id: jonesforth.S,v 1.31 2007-09-25 21:46:20 rich Exp $ gcc -m32 -nostdlib -static -Wl,-Ttext,0 -o jonesforth jonesforth.S */ @@ -783,20 +783,18 @@ code_\label : // assembler code follows push %eax // ignore overflow NEXT - defcode "/",1,,DIV - xor %edx,%edx - pop %ebx - pop %eax - idivl %ebx - push %eax // push quotient - NEXT +/* + In this FORTH, only /MOD is primitive. We define the / and MOD words in + terms of /MOD. +*/ - defcode "MOD",3,,MOD + defcode "/MOD",4,,DIVMOD xor %edx,%edx pop %ebx pop %eax idivl %ebx push %edx // push remainder + push %eax // push quotient NEXT defcode "=",1,,EQU // top two words are equal? @@ -1046,17 +1044,16 @@ code_\label : // assembler code follows NEXT /* ! and @ (STORE and FETCH) store 32-bit words. It's also useful to be able to read and write bytes. - * I don't know whether FORTH has these words, so I invented my own, called !b and @b. * Byte-oriented operations only work on architectures which permit them (i386 is one of those). - * UPDATE: writing a byte to the dictionary pointer is called C, in FORTH. + * UPDATE: writing a byte to the dictionary pointer is called C, (CCOMMA) in FORTH. */ - defcode "!b",2,,STOREBYTE + defcode "C!",2,,STOREBYTE pop %ebx // address to store at pop %eax // data to store there movb %al,(%ebx) // store it NEXT - defcode "@b",2,,FETCHBYTE + defcode "C@",2,,FETCHBYTE pop %ebx // address to fetch xor %eax,%eax movb (%ebx),%al // fetch it @@ -1339,36 +1336,9 @@ _WORD: 5: .space 32 /* - . (also called DOT) prints the top of the stack as an integer in the current BASE. -*/ - - defcode ".",1,,DOT - pop %eax // Get the number to print into %eax - call _DOT // Easier to do this recursively ... - NEXT -_DOT: - mov var_BASE,%ecx // Get current BASE -1: - cmp %ecx,%eax // %eax < BASE? If so jump to print immediately. - jb 2f - xor %edx,%edx // %edx:%eax / %ecx -> quotient %eax, remainder %edx - idivl %ecx - pushl %edx // Print quotient (top half) first ... - call _DOT - popl %eax // ... then loop to print remainder - jmp 1b -2: // %eax < BASE so print immediately. - movl $digits,%edx - addl %eax,%edx - movb (%edx),%al // Note top bits are already zero. - call _EMIT - ret - .section .rodata -digits: .ascii "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" - -/* - Almost the opposite of DOT (but not quite), SNUMBER parses a numeric string such as one returned - by WORD and pushes the number on the parameter stack. + As well as reading in words we'll need to read in numbers and for that we are using a function + called SNUMBER. This parses a numeric string such as one returned by WORD and pushes the + number on the parameter stack. This function does absolutely no error checking, and in particular the length of the string must be >= 1 bytes, and should contain only digits 0-9. If it doesn't you'll get random results.