Improve formatting in small terms.
This change does a few things: 1. Uses .nf and .fi to disable fill during block 2. Shortens block lines likely to wrap 3. Moves instruction stack effect to subsection header
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doc/man/uxntal.7
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doc/man/uxntal.7
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@ -75,14 +75,18 @@ Regular instructions have a single stack effect which is modified in a predictab
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For example the generic effect for \fBADD\fP is ( x y -- x+y ). The eight combinations of modes have the following effects:
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\fBADD\fP ( x^ y^ -- x+y^ ) sum two bytes using \fBwst\fP
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\fBADDr\fP ( [x^ y^] -- [x+y^] ) sum two bytes using \fBrst\fP
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\fBADD2\fP ( x* y* -- x+y* ) sum two shorts using \fBwst\fP
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\fBADD2r\fP ( [x* y*] -- [x+y*] ) sum two shorts using \fBrst\fP
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\fBADDk\fP ( x^ y^ -- x^ y^ x+y^ ) sum two bytes using \fBwst\fP, retain arguments
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\fBADDkr\fP ( [x^ y^] -- [x^ y^ x+y^] ) sum two bytes using \fBrst\fP, retain arguments
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\fBADD2k\fP ( x* y* -- x* y* x+y* ) sum two shorts using \fBwst\fP, retain arguments
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\fBADD2kr\fP ( [x* y*] -- [x* y* x+y*] ) sum two shorts using \fBrst\fP, retain arguments
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.nf
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\fBADD\fP ( x^ y^ -- x+y^ ) sum bytes from \fBwst\fP
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\fBADDr\fP ( [x^ y^] -- [x+y^] ) sum bytes from \fBrst\fP
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\fBADD2\fP ( x* y* -- x+y* ) sum shorts from \fBwst\fP
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\fBADD2r\fP ( [x* y*] -- [x+y*] ) sum shorts from \fBrst\fP
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\fBADDk\fP ( x^ y^ -- x^ y^ x+y^ ) sum and keep bytes from \fBwst\fP
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\fBADDkr\fP ( [x^ y^] -- [x^ y^ x+y^] ) sum and keep bytes from \fBrst\fP
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\fBADD2k\fP ( x* y* -- x* y* x+y* ) sum and keep shorts from \fBwst\fP
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\fBADD2kr\fP ( [x* y*] -- [x* y* x+y*] ) sum and keep shorts from \fBrst\fP
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.fi
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Thus for regular instructions writing a "generic" effect (leaving sigils off values whose size depends on \fIshort mode\fP) is sufficient to describe its behavior across all eight variations. Note that some instructions always read values of a fixed size. For example the boolean condition read by \fBJCN\fP is always one byte, no matter what modes are used.
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@ -98,77 +102,65 @@ We consider the top of the stack to be the first value of the stack, and count b
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.BR
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.SS INC
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( x -- x+1 )
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.SS INC ( x -- x+1 )
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Increment the top value of the stack by 1.
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Overflow will be truncated, so \fB#ff INC\fP will evaluate to \fB0x00\fP.
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.SS POP
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( x -- )
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.SS POP ( x -- )
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Remove the top value of the stack.
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\fBPOPk\fP is guaranteed to have no effect (it will not change the stack).
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.SS NIP
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( x y -- y )
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.SS NIP ( x y -- y )
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Remove the second value of the stack.
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\fBNIPk\fP is guaranteed to have no effect (it will not change the stack).
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.SS SWP
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( x y -- y x )
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.SS SWP ( x y -- y x )
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Swap the top two values of the stack.
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.SS ROT
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( x y z -- y z x )
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.SS ROT ( x y z -- y z x )
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Rotate the top three values of the stack. The lowest becomes the top and the others are each shifted down one place.
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.SS DUP
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( x -- x x )
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.SS DUP ( x -- x x )
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Place a copy of the top value of the stack on top of the stack.
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.SS OVR
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( x y -- x y x )
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.SS OVR ( x y -- x y x )
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Place a copy of the second value of the stack on top of the stack.
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.SS EQU
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( x y -- x==y^ )
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.SS EQU ( x y -- x==y^ )
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Test whether the top two values of the stack are equal.
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Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
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.SS NEQ
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( x y -- x!=y^ )
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.SS NEQ ( x y -- x!=y^ )
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Test whether the top two values of the stack are not equal.
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Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
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.SS GTH
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( x y -- x>y^ )
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.SS GTH ( x y -- x>y^ )
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Test whether the second value of the stack is greater than the top.
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Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
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.SS LTH
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( x y -- x<y^ )
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.SS LTH ( x y -- x<y^ )
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Test whether the second value of the stack is less than the top.
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Result is guaranteed to be boolean (\fB0x00\fP or \fB0x01\fP).
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.SS JMP
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( x -- ; pc <- x )
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.SS JMP ( x -- ; pc <- x )
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Jump to a location.
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@ -178,15 +170,13 @@ It is common to \fBJMP\fP with boolean bytes (0-1) to handle simple conditionals
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@max ( x^ y^ -- max^ ) GTHk JMP SWP POP JMP2r
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.SS JCN
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( x bool^ -- ; pc <- x if bool )
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.SS JCN ( x bool^ -- ; pc <- x if bool )
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Jump to a location when a condition is true.
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The program counter (\fIpc\fP) is updated when \fIbool\fP is non-zero. When \fIx\fP is a byte, it is treated as relative (\fBpc += x\fP) and when \fIx\fP is a short it is treated as absolute (\fBpc = x\fP).
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.SS JSR
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( x -- [pc+1*] )
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.SS JSR ( x -- [pc+1*] )
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Jump to a location, saving a reference to return to.
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@ -194,82 +184,69 @@ Stores the next address to execute before unconditionally updating the program c
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The saved address will always be a short regardless of \fIshort mode\fP.
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.SS STH
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( x -- [x] )
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.SS STH ( x -- [x] )
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Move the top value of the stack to the return stack.
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.SS LDZ
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( zp^ -- x )
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.SS LDZ ( zp^ -- x )
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Load data from a zero-page address (\fB0x00 - 0xff\fP).
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.SS STZ
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( x zp^ -- )
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.SS STZ ( x zp^ -- )
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Store data at a zero-page address (\fB0x00 - 0xff\fP).
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.SS LDR
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( rel^ -- x )
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.SS LDR ( rel^ -- x )
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Load data from a relative address (\fBpc + x\fP).
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Note that unlike \fBLDZk\fP and \fBLDAk\fP the \fBLDRk\fP instruction is not very useful, since a relative address is usually only meaningful when run from a particular address (i.e. for a particular \fIpc\fP value).
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.SS STR
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( x rel^ -- )
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.SS STR ( x rel^ -- )
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Store data at a relative address (\fBpc + x\fP).
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Note that unlike \fBSTZk\fP and \fBSTAk\fP the \fBSTRk\fP instruction is not very useful, since a relative address is usually only meaningful when run from a particular address (i.e. for a particular \fIpc\fP value).
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.SS LDA
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( abs* -- x )
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.SS LDA ( abs* -- x )
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Load data from an absolute address (\fB0x0000 - 0xffff\fP).
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.SS STA
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( x abs* -- )
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.SS STA ( x abs* -- )
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Store data at an absolute address (\fB0x0000 - 0xffff\fP).
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.SS DEI
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( dev^ -- x )
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.SS DEI ( dev^ -- x )
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Read data from a device port (\fB0x00 - 0xff\fP).
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Reading from some ports may have an effect on the underlying VM; in other cases it will simply read values from device memory. See Varvara device documentation for more details.
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.SS DEO
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( x dev^ -- )
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.SS DEO ( x dev^ -- )
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Write data to a device port (\fB0x00 - 0xff\fP).
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Writing to some ports may have an effect on the underlying VM; in other cases it will simply write values to device memory. See Varvara device documentation for more details.
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.SS ADD
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( x y -- x+y )
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.SS ADD ( x y -- x+y )
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Add the top two values of the stack.
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Overflow will be truncated, so \fB#ff #03 ADD\fP will evaluate to \fB0x02\fP.
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.SS SUB
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( x y -- x-y )
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.SS SUB ( x y -- x-y )
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Subtract the top of the stack from the second value of the stack.
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Underflow will be truncated, so \fB#01 #03 SUB\fP will evaluate to \fB0xfe\fP.
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.SS MUL
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( x y -- xy )
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.SS MUL ( x y -- xy )
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Multiply the top two values of the stack.
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Overflow will be truncated, so \fB#11 #11 MUL\fP will evaluate to \fB0x21\fP.
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.SS DIV
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( x y -- x/y )
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.SS DIV ( x y -- x/y )
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Divide the second value of the stack by the top of the stack.
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@ -281,23 +258,19 @@ Unlike \fBADD\fP, \fBSUB\fP, and \fBMUL\fP, \fBDIV\fP does not behave correctly
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There is no \fIremainder\fP instruction, but the phrase \fBDIVk MUL SUB\fP can be used to compute the remainder.
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.SS AND
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( x y -- x&y )
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.SS AND ( x y -- x&y )
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Compute the bitwise union of the top two values of the stack.
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.SS ORA
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( x y -- x|y )
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.SS ORA ( x y -- x|y )
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Compute the bitwise intersection of the top two values of the stack.
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.SS EOR
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( x y -- x^y )
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.SS EOR ( x y -- x^y )
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Compute the bitwise exclusive-or (\fIxor\fP) of the top two values of the stack.
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.SS SFT
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( x rl^ -- (x>>l)<<r )
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.SS SFT ( x rl^ -- (x>>l)<<r )
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Compute a bit shift of the second value of the stack; the directions and distances are determined by the top value of the stack.
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@ -325,7 +298,7 @@ The "immediate jump" instructions are produced by the assembler. They interpret
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\fBJMI\fP ( -- ) jump to \fIaddr\fP unconditionally
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\fBJCI\fP ( bool^ -- ) jump to \fIaddr\fP if \fIbool\fP is non-zero
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\fBJSI\fP ( -- [pc*] ) jump to \fIaddr\fP saving the current address (\fIpc\fP) on the return stack
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\fBJSI\fP ( -- [pc*] ) jump to \fIaddr\fP saving the current address (\fIpc\fP) on \fIrst\fP
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(The instruction pointer will be moved forward 2 bytes, past the relative address.)
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