TH HOC 1
SH NAME
hoc \- interactive floating point language
SH SYNOPSIS
B hoc
[
I file ...
]
[
B -e
I expression
]
SH DESCRIPTION
I Hoc
interprets a simple language for floating point arithmetic,
at about the level of BASIC, with C-like syntax and
functions.
PP
The named
I files
are read and interpreted in order.
If no
I file
is given or if
I file
is
L -
I hoc
interprets the standard input.
The
B -e
option allows input to
I hoc
to be specified on the command line, to be treated as if it appeared in a file.
PP
I Hoc
input consists of
I expressions
and
IR statements .
Expressions are evaluated and their results printed.
Statements, typically assignments and function or procedure
definitions, produce no output unless they explicitly call
IR print .
PP
Variable names have the usual syntax, including
LR _ ;
the name
L _
by itself contains the value of the last expression evaluated.
The variables
BR E ,
BR PI ,
BR PHI ,
BR GAMMA
and
B DEG
are predefined; the last is 59.25..., degrees per radian.
PP
Expressions are formed with these C-like operators, listed by
decreasing precedence.
TP
B ^
exponentiation
TP
B ! - ++ --
TP
B * / %
TP
B + -
TP
B > >= < <= == !=
TP
B &&
TP
B ||
TP
B = += -= *= /= %=
PP
Built in functions are
BR abs ,
BR acos ,
BR asin ,
B atan
(one argument),
BR cos ,
BR cosh ,
BR exp ,
BR int ,
BR log ,
BR log10 ,
BR sin ,
BR sinh ,
BR sqrt ,
BR tan ,
and
BR tanh .
The function
B read(x)
reads a value into the variable
B x
and returns 0 at EOF;
the statement
B print
prints a list of expressions that may include
string constants such as
\fL"hello\en"\f1.\fP
PP
Control flow statements are
BR if - else ,
BR while ,
and
BR for ,
with braces for grouping.
Newline ends a statement.
Backslash-newline is equivalent to a space.
PP
Functions and procedures are introduced by the words
B func
and
BR proc ;
B return
is used to return with a value from a function.
SH EXAMPLES
EX
func gcd(a, b) {
temp = abs(a) % abs(b)
if(temp == 0) return abs(b)
return gcd(b, temp)
}
for(i=1; i<12; i++) print gcd(i,12)
EE
SH SOURCE
B /sys/src/cmd/hoc
SH "SEE ALSO"
IR bc (1),
IR dc (1)
br
B. W. Kernighan and R. Pike,
I
The Unix Programming Environment,
Prentice-Hall, 1984
SH BUGS
Error recovery is imperfect within function and procedure definitions.
