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modules/src/flt_arith/flt_arith.3
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modules/src/flt_arith/flt_arith.3
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.TH FLT_ARITH 3ACK " Fri June 30 1989"
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.ad
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.SH NAME
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flt_arith \- high precision floating point arithmetic
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.SH SYNOPSIS
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.nf
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.B #include <flt_arith.h>
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.PP
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.B flt_add(e1, e2, e3)
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.B flt_arith *e1, *e2, *e3;
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.PP
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.B flt_mul(e1, e2, e3)
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.B flt_arith *e1, *e2, *e3;
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.PP
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.B flt_sub(e1, e2, e3)
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.B flt_arith *e1, *e2, *e3;
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.PP
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.B flt_div(e1, e2, e3)
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.B flt_arith *e1, *e2, *e3;
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.PP
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.B flt_modf(e1, intpart, fractpart)
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.B flt_arith *e1, *intpart, *fractpart;
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.PP
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.B int flt_cmp(e1, e2)
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.B flt_arith *e1, *e2;
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.PP
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.B int flt_str2flt(s, e)
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.B char *s;
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.B flt_arith *e;
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.PP
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.B flt_flt2str(e, buf, bufsize)
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.B flt_arith *e;
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.B char *buf;
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.B int bufsize;
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.PP
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.B int flt_status;
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.PP
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.B #include <em_arith.h>
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.B flt_arith2flt(n, e)
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.B arith n;
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.B flt_arith *e;
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.PP
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.B arith flt_flt2arith(e)
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.B flt_arith *e;
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.SH DESCRIPTION
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This set of routines emulates floating point arithmetic, in a high
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precision. It is intended primarily for compilers that need to evaluate
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floating point expressions at compile-time. It could be argued that this
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should be done in the floating point arithmetic of the target machine,
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but EM does not define its floating point arithmetic.
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.PP
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.B flt_add
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adds the numbers indicated by
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.I e1
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and
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.I e2
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and stores the result indirectly through
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.IR e3 .
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.PP
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.B flt_mul
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multiplies the numbers indicated by
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.I e1
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and
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.I e2
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and stores the result indirectly through
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.IR e3 .
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.PP
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.B flt_sub
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subtracts the number indicated by
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.I e2
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from the one indicated by
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.I e1
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and stores the result indirectly through
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.IR e3 .
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.PP
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.B flt_div
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divides the number indicated by
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.I e1
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by the one indicated by
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.I e2
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and stores the result indirectly through
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.IR e3 .
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.PP
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.B flt_modf
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splits the number indicated by
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.I e
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in an integer and a fraction part, and stores the integer part through
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.I intpart
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and the fraction part through
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.IR fractpart .
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So, adding the numbers indicated by
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.I intpart
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and
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.I fractpart
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results (in the absence of rounding error) in the number
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indicated by
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.IR e .
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Also, the absolute value of the number indicated by
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.I intpart
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is less than or equal to the absolute value of the number indicated by
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.IR e .
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The absolute value of the number indicated by
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.I fractpart
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is less than 1.
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.PP
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.B flt_cmp
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compares the numbers indicated by
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.I e1
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and
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.I e2
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and returns -1 if
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.I e1
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<
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.IR e2 ,
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0 if
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.I e1
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=
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.IR e2 ,
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and 1 if
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.I e1
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>
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.IR e2 .
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.PP
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.B flt_str2flt
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converts the string indicated by
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.I s
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to a floating point number, and stores this number through
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.IR e.
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The string should contain a floating point constant, which consists of
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an integer part, a decimal point, a fraction part, an \f(CWe\fP or an
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\f(CWE\fP, and an optionally signed integer exponent. The integer and
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fraction parts both consist of a sequence of digits. They may not both be
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missing. The decimal point, the \f(CWe\fP and the exponent may be
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missing.
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.PP
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.B flt_flt2str
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converts the number indicated by
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.I e
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into a string, in a scientific notation acceptable for EM. The result is
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stored in
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.IR buf .
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At most
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.I bufsize
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characters are stored.
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.PP
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.B flt_arith2flt
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converts the number
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.I n
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to the floating point format use in this package and returns the result
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in
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.IR e .
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.PP
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.B flt_flt2arith
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truncates the number indicated by
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.I e
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to the largest integer value smaller than or equal to the number indicated by
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.IR e .
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It returns this value.
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.PP
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Before each operation, the
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.I flt_status
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variable is reset to 0. After an operation, it can be checked for one
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of the following values:
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.IP FLT_OVFL
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.br
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an overflow occurred. The result is a large value with the correct sign.
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This can occur with the routines
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.IR flt_add ,
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.IR flt_sub ,
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.IR flt_div ,
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.IR flt_mul ,
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.IR flt_flt2arith ,
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and
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.IR flt_str2flt .
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.IP FLT_UNFL
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.br
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an underflow occurred. The result is 0.
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This can occur with the routines
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.IR flt_div ,
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.IR flt_mul ,
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.IR flt_sub ,
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.IR flt_add ,
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and
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.IR flt_str2flt .
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.IP FLT_DIV0
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.br
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divide by 0. The result is a large value with the sign of the dividend.
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This can only occur with the routine
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.IR flt_div .
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.IP FLT_NOFLT
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.br
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indicates that the string did not represent a floating point number. The
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result is 0.
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This can only occur with the routine
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.IR flt_str2flt .
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.IP FLT_BTSM
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.br
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indicates that the buffer is too small. The contents of the buffer is
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undefined. This can only occur with the routine
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.IR flt_flt2str .
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.SH FILES
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~em/modules/h/flt_arith.h
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.br
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~em/modules/h/em_arith.h
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.br
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~em/modules/lib/libflt.a
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