bitcount(i) returns the number of bits that are set in the integer i. It works only for "normal" integers, not large integers.
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These functions demonstrate the use of external values. extxmin() creates a minimal external type extxstr(s) creates an external hold a string and trivial checksum extxreal(r) creates a fully customized external type holding a real value
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chmod(filename, mode) changes the file permission modes of a file to those specified. umask(mask) sets the process "umask" to the specified value. If mask is omitted, the current process mask is returned.
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fpoll(f, msec) waits until data is available for input from file f, and then returns. It also returns when end-of-file is reached. If msec is specified, and no data is available after waiting that many milliseconds, then fpoll fails. If msec is omitted, fpoll waits indefinitely.
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This file provides three procedures for translating homogeneous
lists of integers, reals, or strings to C arrays:
IListVal(d) returns an array of C ints.
RListVal(d) returns an array of C doubles.
SListVal(d) returns an array of C char pointers (char *).
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These functions provide some access to the internal machinery of the
Icon interpreter. Some knowledge of the interpreter is needed to use
these profitably; misuse can lead to memory violations.
dword(x) return d-word of descriptor
vword(x) return v-word of descriptor
descriptor(d,v) construct descriptor from d-word and v-word
peek(addr,n) return contents of memory as n-character string
(if n is omitted, return Icon integer at addr)
spy(addr,n) return string pointer to memory, without copying
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lgconv(I) converts a large integer into a string using a series of BCD adds. (In contrast, the Icon built-in string() function accomplishes the same conversion using a series of divisions by 10.) lgconv is typically 50% to 75% faster than string() on a Sun or Alpha. For some reason it is as much as 125% SLOWER on a SGI 4/380. lgconv(I) works for all integer values of I. Small integers are simply passed to string() for conversion.
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osftable(id, index, len) returns one element from an OSF table() call.
This function is for the OSF operating system, and fails on other systems.
See "man table" for a detailed description of the "table" system call
and the formats of the structures returned; see /usr/include/table.h
for a list of allowed ID values.
Defaults: index 0
len 100
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s := pack(value, flags, width) x := unpack(string, flags) Flag characters are as follows: l -- little-endian [default] b -- big-endian n -- host platform's native packing order i -- integer [default] u -- unsigned integer r -- real (host platform's native float or double format) The default width is 4. Integer values must fit in a standard Icon integer (not large integer). Consequently, a word-sized value cannot have the high bit set if unsigned. Floating values can only be converted to/from a string width matching sizeof(float) or sizeof(double). Size/type combinations that can't be handled produce errors. Valid combinations produce failure if the value overflows. Some of this code assumes a twos-complement architecture with 8-bit bytes.
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These functions manipulate raw (P6) PPM image files in memory. The images must not contain comment strings. ppmwidth(s) -- return width of PPM image. ppmheight(s) -- return height of PPM image. ppmmax(s) -- return maximum value in PPM header. ppmdata(s) -- return data portion of PPM image. ppmimage(s,p,f) -- quantify image s using palette p, with flags f. Returns an Icon image string. Flag "o" selects ordered dithering. Defaults: p="c6", f="o" ppmstretch(s,lo,hi,max) -- apply contrast stretch operation Returns a PPM string image that results from setting all values <= lo to zero, all values >= hi to max, with values between scaling linearly. If hi = lo + 1, this becomes a simple threshold operation. If lo=0 and hi=ppmmax(s), this simply scales an image to a new maximum. Requirements: 0 <= lo < hi <= ppmmax(s), 1 <= max <= 255. Defaults: lo=0, hi=ppmmax(s), max=255. ppm3x3(s,a,b,c,d,e,f,g,h,i) -- apply 3x3 convolution to PPM image. The matrix of real numbers [[a,b,c],[d,e,f],[g,h,i]] is used as a transformation matrix applied independently to the three color components of the image.
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kill(pid, signal) kill process (defaults: pid=0, signal=SIGTERM) getpid() return process ID getuid() return user ID getgid() return group ID
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tconnect(hostname, portnum) establishes a TCP connection to the given host and port, returning an Icon file f. Note that seek(f) must be called when switching between input and output on this bidirectional file. Additionally, the DEC Alpha requires a call to flush(f), after the seek, when switching from input to output.
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