GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
Unix |
Unix v7 |
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bc(1) |
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bc − arbitrary-precision arithmetic language
bc [ −c ] [ −l ] [ file ... ]
Bc is an interactive processor for a language which resembles C but provides unlimited precision arithmetic. It takes input from any files given, then reads the standard input. The −l argument stands for the name of an arbitrary precision math library. The syntax for bc programs is as follows; L means letter a-z, E means expression, S means statement.
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Comments |
are enclosed in /* and */.
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Names |
simple variables: L
array elements: L [ E ]
The words ’ibase’, ’obase’, and
’scale’
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Other operands |
arbitrarily long numbers with
optional sign and decimal point.
( E )
sqrt ( E )
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length ( E ) |
number of significant decimal digits | |||
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scale ( E ) |
number of digits right of decimal point |
L ( E , ... , E )
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Operators |
+ − * / % ^ (% is
remainder; ^ is power)
++ −− (prefix and postfix; apply to names)
== <= >= != < >
= =+ =− =* =/ =% =^
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Statements |
E
{ S ; ... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit
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Function definitions |
define L ( L ,..., L ) {
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auto L, ... , L | |
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S; ... S | |
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return ( E ) |
}
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Functions in −l |
math library |
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s(x) |
sine |
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c(x) |
cosine |
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e(x) |
exponential |
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l(x) |
log |
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a(x) |
arctangent |
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j(n,x) |
Bessel function |
All function arguments are passed by value.
The value of a statement that is an expression is printed unless the main operator is an assignment. Either semicolons or newlines may separate statements. Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc(1). Assignments to ibase or obase set the input and output number radix respectively.
The same letter may be used as an array, a function, and a simple variable simultaneously. All variables are global to the program. ’Auto’ variables are pushed down during function calls. When using arrays as function arguments or defining them as automatic variables empty square brackets must follow the array name.
For example
scale = 20
define e(x){
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auto a, b, c, i, s |
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a = 1 |
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b = 1 |
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s = 1 |
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for(i=1; 1==1; i++){ |
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a = a*x |
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b = b*i |
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c = a/b |
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if(c == 0) return(s) |
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s = s+c |
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} |
}
defines a function to compute an approximate value of the exponential function and
for(i=1; i<=10; i++) e(i)
prints approximate values of the exponential function of the first ten integers.
Bc is actually a preprocessor for dc(1), which it invokes automatically, unless the −c (compile only) option is present. In this case the dc input is sent to the standard output instead.
/usr/lib/lib.b
mathematical library
dc(1) desk calculator proper
dc(1)
L. L. Cherry and R. Morris, BC − An arbitrary
precision desk-calculator language
No &&,
||, or ! operators.
For statement must have all three E’s.
Quit is interpreted when read, not when executed.
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bc(1) | |