256 lines
4.7 KiB
Text
256 lines
4.7 KiB
Text
.TH DC 1
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.SH NAME
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dc \- desk calculator
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.SH SYNOPSIS
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.B dc
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[
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.I file
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]
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.SH DESCRIPTION
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.I Dc
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is an arbitrary precision desk calculator.
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Ordinarily it operates on decimal integers,
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but one may specify an input base, output base,
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and a number of fractional digits to be maintained.
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The overall structure of
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.I dc
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is
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a stacking (reverse Polish) calculator.
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If an argument is given,
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input is taken from that file until its end,
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then from the standard input.
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The following constructions are recognized:
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.TP
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number
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The value of the number is pushed on the stack.
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A number is an unbroken string of the digits
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.B 0-9A-F
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or
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.BR 0-9a-f .
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A hexadecimal number beginning with a lower case
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letter must be preceded by a zero to distinguish it
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from the command associated with the letter.
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It may be preceded by an underscore
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.B _
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to input a
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negative number.
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Numbers may contain decimal points.
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.TP
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.L
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+ - / * % ^
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Add
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.LR + ,
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subtract
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.LR - ,
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multiply
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.LR * ,
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divide
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.LR / ,
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remainder
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.LR % ,
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or exponentiate
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.L ^
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the top two values on the stack.
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The two entries are popped off the stack;
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the result is pushed on the stack in their place.
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Any fractional part of an exponent is ignored.
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.TP
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.BI s x
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.br
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.ns
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.TP
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.BI S x
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Pop the top of the stack and store into
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a register named
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.IR x ,
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where
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.I x
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may be any character.
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Under operation
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.B S
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register
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.I x
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is treated as a stack and the value is pushed on it.
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.TP
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.BI l x
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.br
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.ns
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.TP
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.BI L x
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Push the value in register
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.I x
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onto the stack.
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The register
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.I x
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is not altered.
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All registers start with zero value.
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Under operation
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.B L
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register
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.I x
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is treated as a stack and its top value is popped onto the main stack.
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.TP
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.B d
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Duplicate the
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top value on the stack.
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.TP
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.B p
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Print the top value on the stack.
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The top value remains unchanged.
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.B P
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interprets the top of the stack as a text
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string,
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removes it, and prints it.
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.TP
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.B f
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Print the values on the stack.
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.TP
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.B q
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.br
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.ns
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.TP
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.B Q
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Exit the program.
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If executing a string, the recursion level is
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popped by two.
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Under operation
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.B Q
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the top value on the stack is popped and the string execution level is popped
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by that value.
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.TP
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.B x
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Treat the top element of the stack as a character string
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and execute it as a string of
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.I dc
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commands.
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.TP
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.B X
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Replace the number on the top of the stack with its scale factor.
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.TP
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.B "[ ... ]"
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Put the bracketed
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text
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string on the top of the stack.
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.TP
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.PD0
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.BI < x
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.TP
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.BI > x
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.TP
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.BI = x
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.PD
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Pop and compare the
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top two elements of the stack.
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Register
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.I x
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is executed if they obey the stated
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relation.
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.TP
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.B v
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Replace the top element on the stack by its square root.
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Any existing fractional part of the argument is taken
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into account, but otherwise the scale factor is ignored.
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.TP
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.B !
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Interpret the rest of the line as a shell command.
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.TP
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.B c
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Clear the stack.
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.TP
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.B i
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The top value on the stack is popped and used as the
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number base for further input.
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.TP
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.B I
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Push the input base on the top of the stack.
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.TP
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.B o
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The top value on the stack is popped and used as the
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number base for further output.
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In bases larger than 10, each `digit' prints as a group of decimal digits.
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.TP
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.B O
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Push the output base on the top of the stack.
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.TP
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.B k
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Pop the top of the stack, and use that value as
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a non-negative scale factor:
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the appropriate number of places
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are printed on output,
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and maintained during multiplication, division, and exponentiation.
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The interaction of scale factor,
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input base, and output base will be reasonable if all are changed
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together.
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.TP
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.B z
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Push the stack level onto the stack.
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.TP
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.B Z
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Replace the number on the top of the stack with its length.
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.TP
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.B ?
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A line of input is taken from the input source (usually the terminal)
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and executed.
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.TP
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.B "; :"
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Used by
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.I bc
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for array operations.
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.PP
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The scale factor set by
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.B k
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determines how many digits are kept to the right of
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the decimal point.
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If
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.I s
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is the current scale factor,
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.I sa
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is the scale of the first operand,
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.I sb
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is the scale of the second,
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and
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.I b
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is the (integer) second operand,
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results are truncated to the following scales.
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.IP
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.nf
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\fL+\fR,\fL-\fR max(\fIsa,sb\fR)
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\fL*\fR min(\fIsa\fR+\fIsb \fR, max\fR(\fIs,sa,sb\fR))
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\fL/\fI s
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\fL%\fR so that dividend = divisor*quotient + remainder; remainder has sign of dividend
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\fL^\fR min(\fIsa\fR\(mu|\fIb\fR|, max(\fIs,sa\fR))
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\fLv\fR max(\fIs,sa\fR)
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.fi
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.SH EXAMPLES
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.LP
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Print the first ten values of
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.IR n !
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.IP
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.EX
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[la1+dsa*pla10>y]sy
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0sa1
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lyx
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.EE
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.SH SOURCE
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.B /sys/src/cmd/dc.c
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.SH "SEE ALSO"
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.IR bc (1),
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.IR hoc (1)
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.SH DIAGNOSTICS
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.I x
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.LR "is unimplemented" ,
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where
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.I x
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is an octal number: an internal error.
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.br
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`Out of headers'
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for too many numbers being kept around.
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.br
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`Nesting depth'
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for too many levels of nested execution.
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.SH BUGS
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When the input base exceeds 16,
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there is no notation for digits greater than
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.BR F .
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.PP
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Past its time.
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